Understanding the dynamics of endocrine changes in the normally aging male is important not only because of the important role hormones play in the maintenance of sexual characteristics and sexual activity, but also for the diagnosis and management of endocrine and metabolic diseases. Data concerning the influence of age on androgens are inconsistent. Several researchers have reported a decrease in free and total testosterone concentrations, whereas others have failed to find age-related changes in testosterone.3,12
Although tT seems to decline slightly with age, we could not find any statistically significant correlation between age groups and the values of tT and fT.
This decline with age is related to decreased Leydig cell mass, decreased testicular perfusion with relative hypoxia and alterations in pituitary-hypothalamic function.13
FSH and LH show an increase with age, but PL has not been studied well in men. Davidson et al and Deslypere et al found no correlation between male PL levels and age, while Vekemans and Robyn reported a slight rise in PRL in 55 to 65 year-old men compared to those 20 years younger.14-16
In this study there was no correlation between age and PL levels.
In hypogonadic men, impaired erection response to visual sexual stimulation prompts consideration of androgens as enhancing erection, but not absolutely necessary.17,18
In 1% of ED cases caused by endocrinological problems, investigating serum testosterone levels once is sufficient when paired with a detailed history and physical examination.19
Johnson and Jarrow found a low incidence of endocrinopathy (2.1%) and noted that decreased libido and/or testicular atrophy would predict this condition with 100% sensitivity.20
They recommended laboratory testing only in patients with decreased libido and/or testicular atrophy. Slag et al studied 187 impotent patients and found no correlation between libido and hypogonadism in 35, while testicular atrophy correlated only with primary hypogonadism.21
In our study group (n = 100), only 42 patients had decreased libido and none of them had any type of endocrinopathy. Moreover, most of these patients had normal values of tT (80.5%) and PL (76%).
Fahmy et al reported that it is very difficult to establish a correlation between ED and serum testosterone levels; and demonstrated that low serum tT levels (< 10 nmol/mL) indicate hypogonadism.18
In the Massachusetts Male Aging Study, testosterone levels were confirmed to decline with age and free testosterone was found to be more predictive than tT.12
It has been suggested that only the measurement of free testosterone is sufficient in ED, and it is not necessary to analyze other hormones.7
Buvat and Lemaire recommended measuring testosterone in all the men > 50 years and in only those men who are < 50 years old but having decreased libido and abnormal physical findings.22
But Ansong et al. found that routine serum tT and fT measurement were not sufficient for decreased libido and ED.13
However, we have found no significant correlation between ED and the values of tT and fT.
Although it seems more likely that decreased libido is a secondary phenomenon related to a defence mechanism in men with ED, in the present study, no statistically significant relation was found between ED and libido. PL levels were found to have a significant relation with decreased libido. Govier et al found a 16% incidence of hypogonadism and 57% of this group had neither decreased libido nor testicular atrophy.7
Baskin reviewed 600 patients and found a 3% incidence of hyperprolactinemia and 7 patients had pituitary tumors (6 with low testosterone).23
Foster et al. found a 3.9% incidence of hyperprolactinemia with 2 pituitary tumors.24
One patient with pituitary tumor had decreased libido and decreased serum testosterone, and 1 had decreased libido but normal serum testosterone. In practice, performing a history and physical examination in conjunction with measurement of testosterone may not be sufficient to diagnose hypogonadism or hyperprolactinemia in these patients.25
Moreover, testosterone levels are not always depressed in endocrinological diseases.18
As such, we suggest that PL should be measured only in patients having any clinical signs and manifestation of endocrinopathy, not in all patients who present to a urology clinic for ED.
Measurement of hormones should be delayed until after taking a detailed history and performing a thorough physical examination. When these findings were evaluated with respect to other studies in the literature, measuring fT and especially PL should provide adequate information.
Taking a detailed medical history and performing a thorough physical examination with history can decrease the need for excessive studies and consultations, saving patients time and unnecessary cost.