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1.  Pretreatment with stress cortisol enhances the human systemic inflammatory response to bacterial endotoxin 
Critical care medicine  2009;37(10):2727.
Objective
There is continuing controversy regarding the effect of glucocorticoids on a systemic inflammatory process. Based on a model of glucocorticoid action that includes both pro- and anti-inflammatory effects, we used the human experimental endotoxemia model to test the hypothesis that a transient elevation of plasma cortisol to stress-associated levels would enhance a subsequent (delayed) systemic inflammatory response to bacterial endotoxin.
Design
Prospective, randomized, double-blind, placebo-controlled clinical investigation.
Setting
Academic medical center.
Subjects
Thirty-six healthy human volunteers.
Interventions
Participants were randomized to receive a 6-hr intravenous infusion of saline (control), an intermediate dose of cortisol (Cort80; 6.3 mg/hr/70 kg), or a high dose of cortisol (Cort160; 12.6 mg/hr/70 kg) on day 1. On day 2, participants received an intravenous injection of 2 ng/kg Escherichia coli endotoxin followed by serial measurements of plasma cytokine concentrations.
Measurements and Main Results
Baseline participant characteristics and cortisol and cytokine concentrations were similar in all three groups. The plasma cortisol response to endotoxemia on day 2 was similar in all three groups. The interleukin-6 response to endotoxemia was significantly increased in the Cort80 Group compared with the control Group (p = .004), whereas the interleukin- 10 response was significantly suppressed (p = .034). Corresponding results for the Cort160 Group were not significantly different from control Group values.
Conclusions
In this study, transient elevation of in vivo cortisol concentrations to levels that are observed during major systemic stress enhanced a subsequent, delayed in vivo inflammatory response to endotoxin. This appeared to be a dose-dependent effect that was more prominent at intermediate concentrations of cortisol than at higher concentrations of cortisol.
PMCID: PMC2819133  PMID: 19885996
cytokine; glucocorticoid; experimental endotoxemia; interleukin-6; sepsis; human
2.  Effect of synthetic ovine corticotropin-releasing factor. Dose response of plasma adrenocorticotropin and cortisol. 
Journal of Clinical Investigation  1983;71(3):587-595.
Synthetic ovine corticotropin-releasing factor (CRF) was administered to normal male volunteer subjects as an intravenous bolus or 30-s infusion. Doses of CRF ranging from 0.001 to 30 micrograms/kg body wt were administered, and plasma immunoreactive (IR)-ACTH and IR-cortisol concentrations were measured. The threshold dose appeared to be 0.01-0.03 micrograms/kg, the half-maximal dose 0.3-1 micrograms/kg, and the maximally effective dose 3-10 micrograms/kg. Basal concentrations of IR-ACTH and IR-cortisol were 14 +/- 7.6 pg/ml (mean +/- SD) and 5.6 +/- 2.2 micrograms/dl, respectively. IR-ACTH rose as early as 2 min after CRF injection, reached peak levels in 10-15 min, and declined slowly thereafter. IR-cortisol rose at 10 min or later and reached peak levels in 30-60 min. At a dose of 30 micrograms/kg, neither IR-ACTH nor IR-cortisol fell from peak levels of 82 +/- 21 pg/ml (mean +/- SE) and 23 +/- 1.4 micrograms/dl, respectively, during the 2-h course of the experiment, indicating that CRF has a sustained effect on ACTH release and/or a prolonged circulating plasma half-life. There was little or no increase in the levels of other anterior pituitary hormones. At doses of 1 microgram/kg and higher, facial flushing, tachycardia, and, in some subjects, a 15-29-mmHg decline in systemic arterial blood pressure were observed, even though blood volume was replaced and the subjects remained supine. These data indicate that synthetic ovine CRF is a very potent and specific ACTH secretagogue in man. Administered with caution until its vasomotor effects are more fully defined, CRF promises to be a safe and very useful investigative, diagnostic, and, possibly, therapeutic agent in man.
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PMCID: PMC436907  PMID: 6298280
3.  Genome Wide Association Identifies Common Variants at the SERPINA6/SERPINA1 Locus Influencing Plasma Cortisol and Corticosteroid Binding Globulin 
PLoS Genetics  2014;10(7):e1004474.
Variation in plasma levels of cortisol, an essential hormone in the stress response, is associated in population-based studies with cardio-metabolic, inflammatory and neuro-cognitive traits and diseases. Heritability of plasma cortisol is estimated at 30–60% but no common genetic contribution has been identified. The CORtisol NETwork (CORNET) consortium undertook genome wide association meta-analysis for plasma cortisol in 12,597 Caucasian participants, replicated in 2,795 participants. The results indicate that <1% of variance in plasma cortisol is accounted for by genetic variation in a single region of chromosome 14. This locus spans SERPINA6, encoding corticosteroid binding globulin (CBG, the major cortisol-binding protein in plasma), and SERPINA1, encoding α1-antitrypsin (which inhibits cleavage of the reactive centre loop that releases cortisol from CBG). Three partially independent signals were identified within the region, represented by common SNPs; detailed biochemical investigation in a nested sub-cohort showed all these SNPs were associated with variation in total cortisol binding activity in plasma, but some variants influenced total CBG concentrations while the top hit (rs12589136) influenced the immunoreactivity of the reactive centre loop of CBG. Exome chip and 1000 Genomes imputation analysis of this locus in the CROATIA-Korcula cohort identified missense mutations in SERPINA6 and SERPINA1 that did not account for the effects of common variants. These findings reveal a novel common genetic source of variation in binding of cortisol by CBG, and reinforce the key role of CBG in determining plasma cortisol levels. In turn this genetic variation may contribute to cortisol-associated degenerative diseases.
Author Summary
Cortisol is a steroid hormone from the adrenal glands that is essential in the response to stress. Most cortisol in blood is bound to corticosteroid binding globulin (CBG). Diseases causing cortisol deficiency (Addison's disease) or excess (Cushing's syndrome) are life-threatening. Variations in plasma cortisol have been associated with cardiovascular and psychiatric diseases and their risk factors. To dissect the genetic contribution to variation in plasma cortisol, we formed the CORtisol NETwork (CORNET) consortium and recruited collaborators with suitable samples from more than 15,000 people. The results reveal that the major genetic influence on plasma cortisol is mediated by variations in the binding capacity of CBG. This is determined by differences in the circulating concentrations of CBG and also in the immunoreactivity of its ‘reactive centre loop’, potentially influencing not only binding affinity for cortisol but also the stability of CBG and hence the tissue delivery of cortisol. These findings provide the first evidence for a common genetic effect on levels of this clinically important hormone, suggest that differences in CBG between individuals are biologically important, and pave the way for further research to dissect causality in the associations of plasma cortisol with common diseases.
doi:10.1371/journal.pgen.1004474
PMCID: PMC4091794  PMID: 25010111
4.  Continuous administration of synthetic ovine corticotropin-releasing factor in man. Physiological and pathophysiological implications. 
Journal of Clinical Investigation  1985;75(6):1781-1785.
The continuous 24-h infusion of a maximally stimulating dose (1 micrograms/kg per h) of ovine corticotropin-releasing factor (CRF) in man caused a modest elevation of plasma cortisol (17.2 +/- 1.4 micrograms/dl) and urinary-free cortisol (173 +/- 43 micrograms/24 h) concentrations, which was far less than that seen with a maximally stimulating dose of ACTH (50.4 +/- 2.2 micrograms/dl and 1,200 +/- 94 micrograms/24 h, respectively). The circadian rhythms of plasma ACTH and cortisol were preserved during CRF administration. An intravenous bolus injection of 1 microgram/kg of ovine CRF given to normal volunteers under basal conditions resulted in elevated plasma ACTH and cortisol peak levels (28 +/- 6 pg/ml and 15.0 +/- 1.0 micrograms/dl, respectively). However, no plasma ACTH and cortisol responses were observed when an identical CRF stimulation test was given at the end of the continuous infusion. These findings suggest that the stimulatory activity of exogenous CRF on the ACTH-secreting cells of the pituitary gland is restrained by the negative feedback of cortisol. The persistent circadian rhythm of ACTH, despite a constant level of plasma CRF during the infusion, suggests that the circadian variation in the activity of the hypothalamic-pituitary-adrenal axis cannot be explained solely by circadian periodicity of the endogenous CRF stimulus.
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PMCID: PMC425532  PMID: 2989331
5.  The effect of oral contraceptives on cortisol metabolism 
The administration of oral contraceptives which contain oestrogen increases non-protein-bound plasma cortisol levels at 9 am as well as protein-bound and total cortisol levels. These increases are dependent on the dose of oestrogen; they are not usually seen with progestogen-only or `low-dose' oestrogen (0·05 mg mestranol or less) preparations. `Standard' oral contraceptives (0·1 mg mestranol or equivalent) produce some elevation of unbound cortisol levels at 9 am (from a normal mean of 0·66 μg/100 ml to 1·02 on the `pill') but this elevation is less than that associated with high-dose oestrogen treatment of, for example, prostate cancer (mean 1·8 μg/100 ml). Since unbound cortisol levels in plasma are controlled by a hypothalamic feedback mechanism, it appears that oral contraceptives have some effect on this mechanism. Possible long-term effects of oral contraceptives on hypothalamopituitary function require examination.
However, the plasma unbound cortisol to which the tissues are exposed at 9 am does not measure the overall exposure of tissues to cortisol throughout the 24 hours. Neither does measurement of cortisol production rate or urinary metabolite excretion accurately reflect the exposure of tissues to cortisol during oestrogen treatment, because of the complex effects of oestrogen on hepatic metabolism of steroids, steroid-protein binding, and the increased size of the extracellular cortisol pool.
The overall exposure of tissues to unbound cortisol is measured better by urinary free cortisol excretion. Urinary free cortisol excretion is a measure of the integrated area under the diurnal curve of plasma unbound cortisol, ie, of the 24-hour exposure of tissues to unbound cortisol. Urinary free cortisol excretion is normal in women taking low-dose oestrogen or progestogen-only contraceptives, and is only trivially increased by the standard `pill'. Thus increased exposure of tissues to unbound cortisol is likely to be only a minor factor in the metabolic responses to oral contraceptives. In contrast, urinary free cortisol excretion (mean normal 38 μg/24 hours) is increased by high-dose oestrogen administration for prostatic cancer (mean 110 μg/24 hours); this is because the diurnal rhythm of unbound cortisol is impaired.
It is thus unwise to ascribe effects of oral contraceptives to increased exposure of tissues to cortisol, except in the liver where it is possible that the increased concentration of protein-bound cortisol they cause may exert metabolic effects. The preparations which cause least change in cortisol metabolism are the low-dose oestrogen or progestogen-only contraceptives.
PMCID: PMC1436049
6.  Cortisol elimination from plasma in premenopausal women with rheumatoid arthritis 
Annals of the Rheumatic Diseases  2003;62(7):674-676.
Methods: Twelve premenopausal female patients with RA (39.8 (1.8) years) and nine healthy control women matched for age and body mass index (42 (3.3) years) were enrolled in the study. None of the patients had previously been receiving treatment with glucocorticoids. After dexamethasone suppression (2 mg by mouth) the evening before the study, 20 mg of hydrocortisone was given. Blood and saliva samples were drawn six hours after injection of hydrocortisone. Plasma and salivary cortisol were measured.
Results: Dexamethasone administration suppressed plasma cortisol concentrations to an almost undetectable level in all subjects, except one with RA. In this subject, a raised concentration of plasma cortisol was verified by repeated analysis despite the fact that cortisol concentration in the saliva sample measured simultaneously was not raised. No significant difference in the disappearance curve of cortisol in plasma or in salivary cortisol levels was found between the patients with RA and the healthy controls.
Conclusions: The profile of disappearance of total cortisol from plasma, and salivary cortisol levels during the elimination phase after its intravenous administration, are unchanged in premenopausal women with RA. Alterations in cortisol clearance are not likely to have a role in cortisol availability in patients with RA.
doi:10.1136/ard.62.7.674
PMCID: PMC1754603  PMID: 12810434
7.  The impact of maternal overnutrition and obesity on hypothalamic-pituitary-adrenal axis, response of offspring to stress 
Domestic animal endocrinology  2012;42(4):195-202.
We evaluated the effect of maternal obesity before and throughout gestation on offspring hypothalamic pituitary adrenal axis function. Multiparous Rambouillet × Columbia crossbred ewes were fed either 100 % of NRC recommendations (Control, C) or 150 % of NRC (Obese, OB) from 60 d before mating until lambing. Ten lambs born to OB ewes (5 males and 5 females), and 8 lambs born to C ewes (3 male and 5 female) were studied. From delivery to weaning lambs were maintained with their mothers who were all fed 100% NRC recommendations. After weaning all lambs were group housed and fed the same diet to meet NRC requirements. At 19 mo of age lambs were placed in individual pens and fed a pelletized diet to meet maintenance requirements. Jugular vein catheters were placed and 2 d later they received an i.v ACTH challenge followed by an i.v. corticotrophin releasing hormone (CRH)/arginine vasopressin (AVP) challenge 1 d later. Thirty d later offspring were again catheterized and placed into metabolism crates for 2 d before receiving an isolation stress test. ACTH and cortisol responses to the isolation stress test and CRH/AVP challenge and cortisol responses to ACTH challenge were determined. Cortisol was quantified via RIA and ACTH was quantified using an Immulite 1000 and both were analyzed using repeated measures utilizing the MIXED procedure of SAS. Offspring from OB ewes had elevated basal plasma ACTH and cortisol compared to C offspring prior to all three challenges (P < 0.05). Offspring from OB mothers tended (P = 0.06) to have a greater ACTH response after an intravenous CRH/AVP injection than offspring from C mothers (12340 ± 1430 vs 8170 ± 1570 area under the curve, respectively). Cortisol response to the CRH/AVP and ACTH challenges was not influenced by maternal nutrition (P < 0.46), and averaged 4.77 ± 0.2 and 1.94 ± .01 μg/dl, respectively. The ACTH response following the isolation stress test was also similar (P = 0.82) for OB and C offspring (147 ± 20 pg/ml). Cortisol response during the isolation stress test was also similar between C and Obese offspring (P = 0.64, 5.25 ± 0.3 μg/dl). These findings suggest that maternal obesity before and during gestation does not affect stress responses by the offspring, but has an impact on hypothalamo-pituitary-adrenal sensitivity. The lack of differences in cortisol release under the influence of difference concentrations of ACTH during the CRH/AVP challenge could indicate adrenal dysfunction in OB offspring.
doi:10.1016/j.domaniend.2011.12.002
PMCID: PMC4206411  PMID: 22264661
maternal obesity; offspring; stress response; hypothalamic-pituitary-adrenal axis; sheep
8.  Plasma, salivary and urinary cortisol levels following physiological and stress doses of hydrocortisone in normal volunteers 
BMC Endocrine Disorders  2014;14(1):91.
Background
Glucocorticoid replacement is essential in patients with primary and secondary adrenal insufficiency, but many patients remain on higher than recommended dose regimens. There is no uniformly accepted method to monitor the dose in individual patients. We have compared cortisol concentrations in plasma, saliva and urine achieved following “physiological” and “stress” doses of hydrocortisone as potential methods for monitoring glucocorticoid replacement.
Methods
Cortisol profiles were measured in plasma, saliva and urine following “physiological” (20 mg oral) or “stress” (50 mg intravenous) doses of hydrocortisone in dexamethasone-suppressed healthy subjects (8 in each group), compared to endogenous cortisol levels (12 subjects). Total plasma cortisol was measured half-hourly, and salivary cortisol and urinary cortisol:creatinine ratio were measured hourly from time 0 (between 0830 and 0900) to 5 h. Endogenous plasma corticosteroid-binding globulin (CBG) levels were measured at time 0 and 5 h, and hourly from time 0 to 5 h following administration of oral or intravenous hydrocortisone. Plasma free cortisol was calculated using Coolens’ equation.
Results
Plasma, salivary and urine cortisol at 2 h after oral hydrocortisone gave a good indication of peak cortisol concentrations, which were uniformly supraphysiological. Intravenous hydrocortisone administration achieved very high 30 minute cortisol concentrations. Total plasma cortisol correlated significantly with both saliva and urine cortisol after oral and intravenous hydrocortisone (P <0.0001, correlation coefficient between 0.61 and 0.94). There was no difference in CBG levels across the sampling period.
Conclusions
An oral dose of hydrocortisone 20 mg is supraphysiological for routine maintenance, while stress doses above 50 mg 6-hourly would rarely be necessary in managing acute illness. Salivary cortisol and urinary cortisol:creatinine ratio may provide useful alternatives to plasma cortisol measurements to monitor replacement doses in hypoadrenal patients.
doi:10.1186/1472-6823-14-91
PMCID: PMC4280712  PMID: 25425285
Adrenal Cortex; HPA axis (hypothalamic-pituitary-adrenal); Cortisol; Hydrocortisone
9.  Cortisol secretion after adrenocorticotrophin (ACTH) and Dexamethasone tests in healthy female and male dogs 
Background
For the conclusive diagnosis of Cushing's Syndrome, a stimulating ACTH test or a low suppressive Dexamethasone test is used. Reports in other species than the dog indicate that plasma cortisol concentration after ACTH administration is affected by gender. We investigated the effect of gender on the cortisol response to ACTH and Dexamethasone tests in dogs.
Methods
Seven healthy adult Cocker Spaniels (4 females and 3 males) were assigned to a two by two factorial design: 4 dogs (2 females and 2 males) received IV Dexamethasone 0.01 mg/kg, while the other 3 dogs received an IV saline solution (control group). Two weeks later the treatments were reversed. After one month, ACTH was given IV (250 μg/animal) to 4 dogs (2 female and 2 males) while the rest was treated with saline solution (control group). Cortisol concentrations were determined by a direct solid-phase radioimmunoassay and cholesterol and triglycerides by commercial kits.
Results and Discussion
No effect of treatment was observed in metabolite concentrations, but females presented higher cholesterol concentrations. ACTH-treated dogs showed an increase in cortisol levels in the first hour after sampling until 3 hours post injection. Cortisol concentrations in Dexamethasone-treated dogs decreased one hour post injection and remained low for 3 hours, thereafter cortisol concentrations increased. The increase in cortisol levels from one to two hours post ACTH injection was significantly higher in females than males. In Dexamethasone-treated males cortisol levels decreased one hour post injection up to 3 hours; in females the decrease was more pronounced and prolonged, up to 5 hours post injection.
Conclusion
We have demonstrated that cortisol response to ACTH and Dexamethasone treatment in dogs differs according to sex.
doi:10.1186/1751-0147-51-33
PMCID: PMC2739526  PMID: 19686591
10.  Arginine vasopressin potentiates adrenocorticotropin release induced by ovine corticotropin-releasing factor. 
Journal of Clinical Investigation  1984;73(2):533-538.
Arginine vasopressin (AVP) stimulates ACTH release in man and acts synergistically with synthetic ovine corticotropin-releasing factor (oCRF) in vitro. This study was designed to examine in man the combined effects of synthetic AVP (10 U intramuscularly) and oCRF (1 micrograms/kg intravenously) on ACTH release. Five normal male volunteers participated in five separate experiments: (a) AVP alone; (b) oCRF alone; (c) AVP followed by oCRF 15 min later; (d) simultaneous AVP and oCRF; and (e) insulin-induced hypoglycemia. Plasma immunoreactive ACTH (IR-ACTH) and IR-cortisol were measured for 4 h after injection of each hormone; basal levels for all subjects were less than or equal to 9 +/- 1.2 pg/ml and 4.9 +/- 0.4 micrograms/dl (mean +/- SE), respectively. AVP and oCRF, when given individually, caused rapid rises in IR-ACTH to similar peak levels of 25 +/- 6.6 and 33 +/- 4.6 pg/ml, respectively. AVP given 15 min before oCRF caused a 2.6-fold potentiation of the oCRF response, with a peak IR-ACTH of 85 +/- 4.6 pg/ml. AVP given at the same time as oCRF produced a fourfold potentiation of the peak IR-ACTH response to 132 +/- 11 pg/ml. These ACTH responses were far greater than those previously observed after 30-fold greater doses of oCRF alone. By way of comparison, insulin-induced hypoglycemia caused a peak IR-ACTH of 169 +/- 20 pg/ml. IR-ACTH returned to base line at 60-90 min after AVP alone, whereas the prolonged effect of oCRF was apparent whether it was given alone or in combination with AVP. The mean peak IR-cortisol responses to AVP, oCRF, and AVP given 15 min before oCRF were similar (16.5 +/- 0.9, 16.4 +/- 2.3, and 18.5 +/- 0.8 micrograms/dl, respectively), but the peak IR-cortisol responses to AVP and oCRF given simultaneously and to insulin-induced hypoglycemia were 1.5 and 1.7 times greater, respectively. IR-cortisol returned to base line within 2-3 h after AVP alone, but remained elevated for at least 4 h after oCRF alone or in combination with AVP. These results indicate that AVP acts synergistically with oCRF to release ACTH in man and suggest that AVP may play a physiologic role in modulating the ACTH response mediated by corticotropin-releasing factor.
PMCID: PMC425045  PMID: 6321557
11.  Increased proteolysis. An effect of increases in plasma cortisol within the physiologic range. 
Journal of Clinical Investigation  1984;73(2):412-420.
Prolonged exposure to glucocorticoids in pharmacologic amounts results in muscle wasting, but whether changes in plasma cortisol within the physiologic range affect amino acid and protein metabolism in man has not been determined. To determine whether a physiologic increase in plasma cortisol increases proteolysis and the de novo synthesis of alanine, seven normal subjects were studied on two occasions during an 8-h infusion of either hydrocortisone sodium succinate (2 micrograms/kg X min) or saline. The rate of appearance (Ra) of leucine and alanine were estimated using [2H3]leucine and [2H3]alanine. In addition, the Ra of leucine nitrogen and the rate of transfer of leucine nitrogen to alanine were estimated using [15N]leucine. Plasma cortisol increased (10 +/- 1 to 42 +/- 4 micrograms/dl) during cortisol infusion and decreased (14 +/- 2 to 10 +/- 2 micrograms/dl) during saline infusion. No change was observed in plasma insulin, C-peptide, or glucagon during either saline or cortisol infusion. Plasma leucine concentration increased more (P less than 0.05) during cortisol infusion (120 +/- 1 to 203 +/- 21 microM) than saline (118 +/- 8 to 154 +/- 4 microM) as a result of a greater (P less than 0.01) increase in its Ra during cortisol infusion (1.47 +/- 0.08 to 1.81 +/- 0.08 mumol/kg X min for cortisol vs. 1.50 +/- 0.08 to 1.57 +/- 0.09 mumol/kg X min). Leucine nitrogen Ra increased (P less than 0.01) from 2.35 +/- 0.12 to 3.46 +/- 0.24 mumol/kg X min, but less so (P less than 0.05) during saline infusion (2.43 +/- 0.17 to 2.84 +/- 0.15 mumol/kg X min, P less than 0.01). Alanine Ra increased (P less than 0.05) during cortisol infusion but remained constant during saline infusion. During cortisol, but not during saline infusion, the rate and percentage of leucine nitrogen going to alanine increased (P less than 0.05). Thus, an increase in plasma cortisol within the physiologic range increases proteolysis and the de novo synthesis of alanine, a potential gluconeogenic substrate. Therefore, physiologic changes in plasma cortisol play a role in the regulation of whole body protein and amino acid metabolism in man.
PMCID: PMC425032  PMID: 6365973
12.  Lack of regulation of 11β-hydroxysteroid dehydrogenase type 1 during short-term manipulation of GH in patients with hypopituitarism 
European Journal of Endocrinology  2009;161(3):375-380.
Objective
Evidence from long-term clinical studies measuring urinary steroid ratios, and from in vitro studies, suggests that GH administered for longer than 2 months down-regulates 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), thereby reducing cortisol regeneration in liver and adipose tissue. We aimed to measure acute effects of GH on 11β-HSD1 in liver and adipose tissue in vivo, including using a stable isotope tracer.
Design
Observational studies of GH withdrawal and reintroduction in patients with hypopituitarism.
Methods
Twelve men with benign pituitary disease causing GH and ACTH deficiency on stable replacement therapy for >6 months were studied after GH withdrawal for 3 weeks, and after either placebo or GH injections were reintroduced for another 3 weeks. We measured cortisol kinetics during 9,11,12,12-2H4-cortisol (d4-cortisol) infusion, urinary cortisol/cortisone metabolite ratios, liver 11β-HSD1 by appearance of plasma cortisol after oral cortisone, and 11β-HSD1 mRNA levels in subcutaneous adipose biopsies.
Results
GH withdrawal and reintroduction had no effect on 9,12,12-[2H]3-cortisol (d3-cortisol) appearance, urinary cortisol/cortisone metabolite ratios, initial appearance of cortisol after oral cortisone, or adipose 11β-HSD1 mRNA. GH withdrawal increased plasma cortisol 30–180 min after oral cortisone, increased d4-cortisol clearance, and decreased relative excretion of 5α-reduced cortisol metabolites.
Conclusions
In this setting, GH did not regulate 11β-HSD1 rapidly in vivo in humans. Altered cortisol metabolism with longer term changes in GH may reflect indirect effects on 11β-HSD1. These data do not suggest that glucocorticoid replacement doses need to be increased immediately after introducing GH therapy to compensate for reduced 11β-HSD1 activity, although dose adjustment may be required in the longer term.
doi:10.1530/EJE-09-0315
PMCID: PMC2754375  PMID: 19549748
13.  Quantitative Relations of Fetal and Maternal Pitiutary - Adrenal Systems I. EFFECTS OF MATERNAL HYPOPHYSECTOMY 
Journal of Clinical Investigation  1973;52(12):3154-3160.
Even though certain aspects of the fetal pituitary-adrenal system have been extensively studied, much remains to be learned of its basic development and function. In the present work, the effect of maternal hypophysectomy upon quantitative pituitary-adrenal relations in mother and fetus was investigated in pregnant beagle dogs. At 57 days gestation in each of seven normal animals and seven animals 3 wk posthypophysectomy, a cannula for collection of adrenal effluent was placed in a single fetus in utero under halothane anesthesia. A timed fetal adrenal sample was obtained; ACTH (10 mU) was injected into the fetus; 3 min thereafter a second fetal adrenal sample was collected and fetal and maternal peripheral arterial samples were drawn. All fetuses and their adrenal glands were weighed. Concentrations of cortisol and corticosterone were determined by a modification of the double-isotope dilution derivative method of Kliman and Peterson.
Mean peripheral cortisol concentrations in mother and fetus were 92 and 94 ng/ml, respectively (ratio 1.0), in normal pregnancies and 11 and 54 ng/ml, respectively (ratio 0.2), in maternal hypophysectomy pregnancies. Weights of fetal adrenal gland pairs of 32 and 44 mg, respectively, in normal and hypophysectomy pregnancies indicate increased fetal ACTH secretion in response to lowered circulating cortisol in the fetus secondary to maternal hypophysectomy. These data demonstrate the presence of an active pituitary-adrenal feedback mechanism in the dog fetus which is partly influenced by maternal pituitary-adrenal function. The shift in the maternal-fetal ratio of peripheral cortisol concentrations from 1.0 to 0.2 occasioned by maternal hypophysectomy neither supports nor rules out the presence of specific placental mechanisms affecting relative concentrations of cortisol in mother and fetus. It does suggest, however, that the relative steroid input into maternal and fetal compartments is one of the factors which influences such concentration ratios. Concentrations of cortisol were significantly higher in fetal adrenal effluent (pre-ACTH) than in fetal peripheral plasma in normal pregnancies, which demonstrates secretion of cortisol by the fetus and shows that corticosteroid of maternal origin does not lead to complete suppression of fetal pituitary-adrenal function. Cortisol secretion rates in response to exogenous ACTH were essentially the same in fetuses in normal and hypophysectomy pregnancies (132 and 128 ng/min, respectively). Thus, fetal adrenal responsiveness to ACTH, i.e., maximum secretory capacity, is not enhanced by increased ACTH stimulation sufficient to induce adrenal hypertrophy in the same fetuses.
Images
PMCID: PMC302591  PMID: 4356264
14.  Neural Control of Counter-Regulatory Events during Glucopenia in Man 
Journal of Clinical Investigation  1973;52(8):1841-1844.
The effect of autonomic denervation on the metabolic and hormonal responses during intracellular glucopenia in man was investigated. 2-Deoxy-d-glucose (2 DG), a competitive inhibitor of glucose metabolism, was administered intravenously to nine normal volunteers and to five patients, three with complete cervical cord transection (C-6) and two with idiopathic orthostatic hypotension. Before, during, and after a 20 min infusion of 2 DG (50 mg/kg) plasma concentrations of glucose, lactate, FFA, total catecholamines, immunoreactive insulin (IRI), human growth hormone (HGH), and cortisol were determined for periods up to 150 min. In control subjects, the initial elevation of FFA, glucose. HGH, and cortisol corresponded with the rise in total catecholamines, with maximal levels attained at 60 min, lactate rose at a slower rate, reaching peak levels at 150 min: although no change in IRI was noted. In contrast, 2 DG-induced glucopenic stress in the autonomic denervated subjects was characterized by no detectable catecholamine release or significant rise in glucose, FFA, lactate, or IRI. However, HGH and cortisol responses in four of the five patients were of a similar or greater magnitude than controls.
These studies demonstrate that the integrity of the sympathoadrenomedullary axis is essential for the counter-regulatory response to intracellular glucopenia in man. Cortisol and HGH have no apparent role in these events.
Images
PMCID: PMC302464  PMID: 4719665
15.  Effects of Elevated Circulating Cortisol Concentrations on Maternal Behavior in Common Marmoset Monkeys (Callithrix jacchus) 
Psychoneuroendocrinology  2009;34(8):1222-1234.
Summary
Both acute and chronic stress can impair maternal behavior and increase rates of infant abuse in several species. The mechanisms inducing these effects are unknown, but experimental manipulation of circulating corticosterone levels alters maternal behavior in rats, and circulating or excreted cortisol concentrations have been found to correlate either positively or negatively with maternal behavior in humans and nonhuman primates. In this study, therefore, we experimentally tested the hypothesis that both acute and chronic treatment with exogenous glucocorticoids would alter maternal behavior in a primate, the common marmoset (Callithrix jacchus). Multiparous females, approximately 3−5 weeks postpartum, received daily injections of either cortisol (hydrocortisone sodium succinate and hydrocortisone acetate; N = 7) or vehicle (N = 7) for 8 days, and maternal behavior was characterized under baseline conditions as well as during exposure to a noise stressor. Cortisol treatment successfully elevated both morning and afternoon plasma cortisol concentrations and suppressed circulating levels of adrenocorticotropic hormone. In home-cage observations, cortisol-treated females carried their infants significantly less than control mothers, and in noise-stressor tests, several hours after the first cortisol or vehicle treatment, cortisol-treated mothers inspected their infants significantly more often than controls. Aggression towards infants was infrequent and mild, and did not differ between treatment groups. These findings provide the first experimental evidence that cortisol elevations can alter maternal behavior in primates. As these effects were limited in scope, however, they suggest that other stress-responsive hormones or neuropeptides may additionally play a role in mediating the effects of stress on maternal behavior.
doi:10.1016/j.psyneuen.2009.03.012
PMCID: PMC2716431  PMID: 19362777
common marmoset; stress; maternal behavior; glucocorticoids; infant abuse; infant neglect
16.  The fetal sheep lung does not respond to cortisol infusion during the late canalicular phase of development 
Physiological Reports  2013;1(6):e00130.
The prepartum surge in plasma cortisol concentrations in humans and sheep promotes fetal lung and surfactant system maturation in the support of air breathing after birth. This physiological process has been used to enhance lung maturation in the preterm fetus using maternal administration of betamethasone in the clinical setting in fetuses as young as 24 weeks gestation (term = 40 weeks). Here, we have investigated the impact of fetal intravenous cortisol infusion during the canalicular phase of lung development (from 109- to 116-days gestation, term = 150 ± 3 days) on the expression of genes regulating glucocorticoid (GC) activity, lung liquid reabsorption, and surfactant maturation in the very preterm sheep fetus and compared this to their expression near term. Cortisol infusion had no impact on mRNA expression of the corticosteroid receptors (GC receptor and mineralocorticoid receptor) or HSD11B-2, however, there was increased expression of HSD11B-1 in the fetal lung. Despite this, cortisol infusion had no effect on the expression of genes involved in lung sodium (epithelial sodium channel -α, -β, or -γ subunits and sodium–potassium ATPase-β1 subunit) or water (aquaporin 1, 3, and 5) reabsorption when compared to the level of expression during exposure to the normal prepartum cortisol surge. Furthermore, in comparison to late gestation, cortisol infusion does not increase mRNA expression of surfactant proteins (SFTP-A, -B, and -C) or the number of SFTP-B-positive cells present in the alveolar epithelium, the cells that produce pulmonary surfactant. These data suggest that there may be an age before which the lung is unable to respond biochemically to an increase in fetal plasma cortisol concentrations.
doi:10.1002/phy2.130
PMCID: PMC3871449  PMID: 24400136
Glucocorticoid; liquid reabsorption; lung; preterm; surfactant
17.  Dose related in vitro effects of ranitidine and cimetidine on basal and ACTH-stimulated steroidogenesis. 
Gut  1986;27(10):1143-1146.
Isolated bovine adrenocortical cells were incubated with and without 3 ng/ml ACTH, with various concentrations (10-1000 micrograms/ml) of either cimetidine or ranitidine. Cortisol, corticosterone, and deoxycorticosterone outputs were measured. Cimetidine and ranitidine at 320 and 1000 micrograms/ml inhibited ACTH-stimulated corticosterone and cortisol synthesis and cimetidine decreased basal cortisol synthesis. The inhibitory effects of cimetidine on cortisol synthesis were approximately 10 times greater than those of ranitidine. Cimetidine (1000 micrograms/ml), but not ranitidine increased deoxycorticosterone synthesis by ACTH-stimulated cells, indicating inhibition of 11 beta-hydroxylation in the adrenal steroidogenic pathway. Although doses of cimetidine and ranitidine which produce these in vitro effects are much greater than plasma concentrations in normal clinical use, they might be important in acutely ill patients given intravenous bolus injections of cimetidine, or if either antagonist were accumulated by the adrenal to produce high intracellular concentrations.
PMCID: PMC1433889  PMID: 3023203
18.  Measurement of tissue cortisol levels in patients with severe burns: a preliminary investigation 
Critical Care  2009;13(6):R189.
Introduction
The assessment of adrenal function in critically ill patients is problematic, and there is evidence to suggest that measurement of tissue glucocorticoid activity may be more useful than estimation of plasma cortisol concentrations. Interstitial cortisol concentrations of cortisol represent the available pool of glucocorticoids able to enter the cell and bind to the glucocorticoid receptor. However the concentrations of plasma cortisol may not accurately reflect interstitial concentrations. We elected to perform a preliminary study into the feasibility of measuring interstitial cortisol by microdialysis, and to investigate the relationship between total plasma cortisol, free plasma cortisol and interstitial cortisol in patients with severe burns.
Methods
A prospective observational study carried out in a tertiary intensive care unit. Ten adult patients with a mean total burn surface area of 48% were studied. Interstitial cortisol was measured by microdialysis from patient-matched burnt and non-burnt tissue and compared with that of 3 healthy volunteers. Plasma sampling for estimations of total and free cortisol concentrations was performed concurrently.
Results
In the burn patients, mean total plasma and free plasma cortisol concentrations were 8.8 +/- 3.9, and 1.7 +/- 1.1 mcg/dL, (p < 0.001), respectively. Mean subcutaneous microdialysis cortisol concentrations in the burn and non-burn tissue were 0.80 +/- 0.31 vs 0.74 +/- 0.41 mcg/dL (p = 0.8), respectively, and were significantly elevated over the mean subcutaneous microdialysis cortisol concentrations in the healthy volunteers. There was no significant correlation between total plasma or free plasma and microdialysis cortisol concentrations. Plasma free cortisol was better correlated with total burn surface area than total cortisol.
Conclusions
In this preliminary study, interstitial cortisol concentrations measured by microdialysis in burnt and non-burnt skin from patients with severe thermal injury are significantly elevated over those from healthy volunteers. Plasma estimations of cortisol do not correlate with the microdialysis levels, raising the possibility that plasma cortisol may be an unreliable guide to tissue cortisol activity.
doi:10.1186/cc8184
PMCID: PMC2811946  PMID: 19943926
19.  Physiologic changes in maternal cortisol do not alter expression of growth-related genes in the ovine placenta 
Placenta  2010;31(12):10.1016/j.placenta.2010.09.010.
Objectives
The aim of this study was to investigate the effect of cortisol on growth-related genes in the ovine placenta.
Study design
Ewes carrying singleton pregnancies were operated on between 112 and 116 days of gestation (115 ± 0.4, term=147 days) and randomly assigned into three groups: six control animals, five ewes that were administered cortisol by continuous intravenous infusion (1 mg/kg/day) (high cortisol), and five ewes that were adrenalectomized and replaced with 0.5–0.6 mg cortisol/kg/day and 3 μg aldosterone/kg/day to produce cortisol concentrations equivalent to pre-pregnancy values (low cortisol). At necropsy (130 ± 0.2 days of gestation), placental tissue was frozen and stored at −80°C for mRNA analysis.
Main outcome measures
To assess potential molecular mechanisms by which cortisol alters placental structure and function and fetal growth.
Results
Cortisol levels did not significantly affect 11β-hydroxysteroid dehydrogenase 1 and 2 enzymes, glucocorticoid receptor, mineralocorticoid receptor and angiotensin II receptor, type 1 (AT1R) expression levels. Gene expression levels of AT2R were increased in the high cortisol group for type B placentomes. There was little effect of cortisol on the insulin-like growth factor (IGF) axis. There was significantly more IGF-I mRNA in B versus A type and more IGFBP-2 mRNA in B and C type versus A type placentomes regardless of treatment (p<0.05).
Conclusions
These data suggest that cortisol affects AT2R expression at high concentrations. Cortisol had little effect on the IGF axis in the placenta. However, the IGF axis might be involved in remodeling the fetal zone of placentomes during normal development.
doi:10.1016/j.placenta.2010.09.010
PMCID: PMC3870879  PMID: 20951429
cortisol; placentomes; insulin-like growth factor; angiotensin receptor
20.  Cortisol Interferes with the Estradiol-Induced Surge of Luteinizing Hormone in the Ewe1 
Biology of Reproduction  2009;80(3):458-463.
Two experiments were conducted to test the hypothesis that cortisol interferes with the positive feedback action of estradiol that induces the luteinizing hormone (LH) surge. Ovariectomized sheep were treated sequentially with progesterone and estradiol to create artificial estrous cycles. Cortisol or vehicle (saline) was infused from 2 h before the estradiol stimulus through the time of the anticipated LH surge in the artificial follicular phase of two successive cycles. The plasma cortisol increment produced by infusion was ∼1.5 times greater than maximal concentrations seen during infusion of endotoxin, which is a model of immune/inflammatory stress. In experiment 1, half of the ewes received vehicle in the first cycle and cortisol in the second; the others were treated in reverse order. All ewes responded with an LH surge. Cortisol delayed the LH surge and reduced its amplitude, but both effects were observed only in the second cycle. Experiment 2 was modified to provide better control for a cycle effect. Four treatment sequences were tested (cycle 1-cycle 2): vehicle-vehicle, cortisol-cortisol, vehicle-cortisol, cortisol-vehicle. Again, cortisol delayed but did not block the LH surge, and this delay occurred in both cycles. Thus, an elevation in plasma cortisol can interfere with the positive feedback action of estradiol by delaying and attenuating the LH surge.
An elevation in plasma cortisol interferes with the positive feedback action of estradiol in the ewe by delaying and attenuating the induced LH surge.
doi:10.1095/biolreprod.108.074252
PMCID: PMC2805396  PMID: 19056703
cortisol; estradiol; glucocorticoid; LH surge; luteinizing hormone; positive feedback; stress
21.  Antepartum depression severity is increased during seasonally longer nights: Relationship to melatonin and cortisol timing and quantity 
Chronobiology international  2013;30(9):1160-1173.
Current research suggests that mood varies from season to season in some individuals, in conjunction with light-modulated alterations in chronobiologic indices like melatonin and cortisol. The primary aim of this study was to evaluate the effects of seasonal variations in darkness on mood in depressed antepartum women, and to determine the relationship of seasonal mood variations to contemporaneous blood melatonin and cortisol measures; a secondary aim was to evaluate the influence of seasonal factors on measures of melancholic versus atypical depressive symptoms. We obtained measures of mood and overnight concentrations of plasma melatonin and serum cortisol in 19 depressed patients (DP) and 12 healthy control (HC) antepartum women, during on-going seasonal variations in daylight/darkness, in a cross-sectional design. Analyses of variance showed that in DP, but not HC, Hamilton Depression Rating Scale (HRSD) scores were significantly higher in women tested during seasonally longer vs. shorter nights. This exacerbation of depressive symptoms occurred when the dim light melatonin onset, the melatonin synthesis offset and the time of maximum cortisol secretion (acrophase) were phase-advanced (temporally shifted earlier), and melatonin quantity was reduced, in DP but not HC. Serum cortisol increased across gestational weeks in both the HC and DP groups, which did not differ significantly in cortisol concentration. Nevertheless, serum cortisol concentration correlated positively with HRSD score in DP but not HC; notably, HC showed neither significant mood changes nor altered melatonin and cortisol timing or quantity in association with seasonal variations. These findings suggest that depression severity during pregnancy may become elevated in association with seasonally-related phase-advances in melatonin and cortisol timing and reduced melatonin quantity that occur in DP, but not HC. Thus, women who experience antepartum depression may be more susceptible than their non-depressed counterparts to phase alterations in melatonin and cortisol timing during seasonally longer nights. Interventions that phase delay melatonin and/or cortisol timing -- for example, increased exposure to bright evening light -- might serve as an effective intervention for antepartum depressions whose severity is increased during seasonally longer nights.
doi:10.3109/07420528.2013.808652
PMCID: PMC4041493  PMID: 23998286
Pregnant depression; chronobiology; season; circadian rhythm; darkness
22.  Diurnal Variation in the Responsiveness of Human Subjects to Human Growth Hormone 
Journal of Clinical Investigation  1973;52(4):912-918.
The objective of this study was to compare the responsiveness of human subjects to the anabolic effects of human growth hormone (HGH) administered at 8 a.m. or at 11 p.m. Three doses of HGH were used: A, 0.0168 U/kg body weight (BW)3/4 per day; B, 0.0532 U/kg BW3/4 per day; C, 0.168 U/kg BW3/4 per day. The effect of each dose on daily balances of N, P, Na, and K and on BW was measured. The subjects were of two groups: (a) seven GH-deficient children, of whom three were deficient in ACTH; and (b) three patients with limb-girdle dystrophy. ACTH-deficient patients in group (a) received exogenous cortisol at 7 a.m. In all 10 subjects, the anabolic effects of dose C, and sometimes of B and A, administered at 11 p.m. were significantly (P < 0.05) greater than when administered at 8 a.m. In these experiments plasma cortisol concentration averaged 3 times greater at 8 a.m. than at 11 p.m.
In the next experiments, exogenous cortisol was administered to the three ACTH-deficient patients at 10 p.m. and the responsiveness to HGH injected at 11 p.m. vs. 8 a.m. was again compared. Under these conditions, when plasma cortisol concentration averaged 3 times greater at 11 p.m. than at 8 a.m., HGH injected at 8 a.m. caused significantly greater anabolic responses than HGH injected at 11 p.m.
These findings indicate that the magnitude of the anabolic response to exogenous HGH is inversely related to the plasma cortisol concentration at the time of HGH injection.
PMCID: PMC302339  PMID: 4693655
23.  Altered Methylprednisolone Pharmacodynamics in Healthy Subjects With Histamine N-Methyltransferase C314T Genetic Polymorphism 
Journal of clinical pharmacology  2006;46(4):408-417.
This study investigated the potential differences in methylprednisolone pharmacodynamics between healthy subjects with different histamine N-methyltransferase (HNMT) C314T genotypes. Six individuals with C/C genotype and 4 with C/T genotype were administered a single intravenous dose of methylprednisolone 0.6 mg/kg ideal body weight in a randomized 2-period manner. Methylprednisolone plasma concentrations were fitted with a 1-compartment model. Cortisol and whole blood histamine suppression were assessed by indirect response models, with circadian baseline cortisol analyzed by Fourier analysis. The area between the baseline and effect curve and the area under the effect versus time curve suppression ratiowere used to characterize plasma histamine suppression. Methylprednisolone pharmacokinetics and plasma and whole blood histamine suppression were similar between the 2 genotype groups. Median nadir of cortisol and the 50% inhibitory concentration for cortisol were significantly higher in subjects with C/T genotype than those with C/C genotype (P = .031 and .033, respectively, Wilcoxon rank sum test). Subjects who are heterozygous for the T314 variant allele thus appeared less sensitive to the suppressive effects of methylprednisolone on cortisol secretion.
doi:10.1177/0091270006286434
PMCID: PMC4196422  PMID: 16554448
Corticosteroids; methylprednisolone pharmacodynamics; cortisol suppression; histamine suppression; HNMT polymorphism
24.  The Relationship Between Fluticasone Furoate Systemic Exposure and Cortisol Suppression 
Clinical Pharmacokinetics  2013;52(10):885-896.
Introduction
The inhaled corticosteroid (ICS) fluticasone furoate is in development, in combination with the long-acting beta2-agonist vilanterol for the once-daily treatment of asthma and chronic obstructive pulmonary disease and as a monotherapy treatment for asthma. Corticosteroids, including ICSs, have the potential to induce dose-dependent systemic effects on the hypothalamic–pituitary–adrenal (HPA) axis. Cortisol suppression has been observed in asthma patients with normal HPA axis function at baseline on receiving high doses of ICSs, and is associated with adverse effects on a number of physiological processes. The measurement of 24-h serum cortisol and 24-h urinary cortisol excretion are sensitive methods for assessing adrenocortical activity, and can evaluate cortisol suppression in a dose-dependent manner.
Objective
The purpose of the meta-analysis presented here was to characterize the population pharmacokinetic/pharmacodynamic relationship between fluticasone furoate systemic exposure [as measured by area under the concentration–time curve over 24 h postdose (AUC24)] and both 24-h weighted mean serum cortisol (WM24) and 24-h urine cortisol excretion in healthy subjects and subjects with asthma.
Methods
The serum cortisol meta-analysis integrated eight studies; five Phase I studies in healthy subjects, two Phase IIa studies, and one Phase III study in subjects with asthma. Each study included serial blood sampling for estimation of WM24. The urine cortisol meta-analysis integrated three studies: one Phase I study in healthy subjects, and one Phase IIb and one Phase III study in subjects with asthma. Each study included complete 0–24 h urine collection for estimation of urine cortisol excretion. All studies included blood sampling for estimation of fluticasone furoate AUC24. A sigmoid maximum effect (Emax) model was fitted to fluticasone furoate AUC24 and serum cortisol and urine cortisol data using nonlinear mixed-effect modeling with the computer program NONMEM®.
Results
Over a wide range of systemic fluticasone furoate exposure representing the therapeutic and supratherapeutic range, the relationship between fluticasone furoate AUC24 and WM24 and 24-h urine cortisol excretion was well described by an Emax model. The average estimate of AUC producing 50 % of maximum effect (AUC50) was similar for the serum cortisol and urine cortisol models with values of 1,556 and 1,686 pg·h/mL, respectively. Although formulation/inhaler was shown to be a significant covariate on the estimates of both WM24 at zero concentration (C0) and AUC50 in the serum cortisol model, the differences were small and believed to be due to study variability. Age was shown to be a significant covariate on the estimates of both C0 and AUC50 in the urine cortisol model, and was considered to be a reflection of lower urine cortisol excretion in adolescents.
Conclusion
A pharmacokinetic/pharmacodynamic model has been established over a wide range of systemic fluticasone furoate exposure representing the therapeutic and supratherapeutic range to both WM24 and 24-h urine cortisol excretion. The values of AUC50 of 1,556 and 1,686 pg·h/mL, respectively, are several times higher than average fluticasone furoate AUC24 values observed at clinical doses of fluticasone furoate (≤200 μg). The models predict a fluticasone furoate AUC24 of 1,000 pg·h/mL would be required to reduce 24-h serum cortisol or 24-h urine cortisol excretion by 20 and 17 %, respectively.
doi:10.1007/s40262-013-0078-1
PMCID: PMC3779313  PMID: 23719680
25.  Adrenocorticotropic hormone stimulation tests in healthy foals from birth to 12 weeks of age 
The purpose of this study was to investigate total baseline plasma cortisol and adrenocorticotropic hormone (ACTH) concentrations, and ACTH-stimulated cortisol concentrations in foals from birth to 12 wk of age. Plasma (baseline) cortisol and ACTH concentrations were measured in 13 healthy foals at birth and at 1, 2, 3, 4, 5, 7, 10, 14, 21, 28, 42, 56, and 84 d of age. Each foal received cosyntropin (0.1 μg/kg) intravenously. Plasma cortisol concentrations were measured before (baseline), and 30, and 60 min after cosyntropin administration at birth and at 3, 5, 7, 10, 14, 21, 28, 42, 56, and 84 d of age. Compared with baseline, cortisol concentration increased significantly 30 min after administration of cosyntropin on all days. Cortisol concentration was highest at birth, measured at 30 and 60 min after cosyntropin administration, compared with all other days. With the exception of birth measurements, cortisol concentration was significantly higher on day 84, measured at 30 and 60 min after cosyntropin administration, when compared with all other days. Baseline plasma ACTH was lowest at birth when compared with concentrations on days 2, 3, 4, 5, 7, 10, 14, 42, 56, and 84. Administration of 0.1 μg/kg of cosyntropin, IV, reliably induces cortisol secretion in healthy foals. Differences in the magnitude of response to cosyntropin are observed depending on the age of the foal. These data should serve as a reference for the ACTH stimulation test in foals and should be useful in subsequent studies to evaluate the hypothalamic-pituitary-adrenal axis in healthy and critically ill foals.
PMCID: PMC2613599  PMID: 19337398

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