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We read with great interest the paper by Tirgar-Tabari et al. published in the International Journal of Trichology in August 2016 regarding the role of hyperprolactinemia in the onset of hirsutism. We would like to point out important aspects related to the evaluation of the levels of prolactin (PRL).
Venipuncture stress may induce transient elevations in serum PRL. For this reason, clinical guidelines recommend obtaining 2–3 blood samples separated by 15–20 minutes to correctly determine its levels. Therefore, routine blood tests taken after a 12 h overnight fasting, as the authors performed, are not valid to determine hyperprolactinemia. Normal PRL levels in women and men are below 25 ng/ml and 20 ng/ml, respectively.[2,3] The authors considered high levels of PRL when its value exceeded 27 ng/ml. Nevertheless, serum PRL levels between 20 and 40 ng/ml may be a result of physiological conditions such as physical activity, emotional or physical stress, and even sleep.[2,3] Patients with higher serum levels of PRL than 20 ng/ml but below 40 ng/ml should have their laboratory test repeated to confirm hyperprolactinemia.
Secondary causes of hyperprolactinemia must be ruled out by a detailed clinical history (with emphasis on psychoactive drugs use), physical examination, evaluation of kidney and liver function by routine biochemical analysis, thyroid-stimulating hormone (TSH) determination, and a pregnancy test. The authors apparently only performed TSH determination to discard secondary causes of increased levels of PRL.
In conclusion, to stablish a diagnosis of isolated hyperprolactinemia an adequate laboratory assessment must be performed, and secondary causes of hyperprolactinemia should be excluded. The effort of the authors stressed the need of further studies to evaluate the role of the PRL in hair growth correctly.
There are no conflicts of interest.