A neutral effect of testosterone therapy on macroprolactin content in men with macroprolactinemia and late-onset hypogonadism

Background: In the light of recent studies, macroprolactinemia seems to occur much more frequently than previously thought. In women, oral contraceptive pills exhibit a stimulatory effect on macroprolactin production. No previous study has investigated macroprolactin levels in androgen treated hypogonadal men. Methods: We studied 10 men with isolated macroprolactinemia and 14 men with normal prolactin levels who because of late-onset hypogonadism were treated with intramuscular testosterone enanthate. Serum prolactin, macroprolactin content, serum testosterone and gonadotropin levels were assessed at baseline and after 4 months of therapy. Results: Although baseline levels of testosterone and gonadotropins were similar in men with and without macroprolactinemia, clinical symptoms were more severe in patients with elevated big-big prolactin levels. As expected, testosterone treatment increased serum testosterone, slightly reduced serum gonadotropins, as well as improved clinical condition in both patients with and without macroprolactinemia, with no difference between the groups. However, testosterone therapy did not affect serum prolactin and macroprolactin content, even after replacing intramuscular testosterone enanthate with oral testosterone undecanoate. Conclusions: Our results suggest a negligible effect of testosterone replacement on macroprolactin levels in macroprolactinemic men with late-onset hypogonadism. (c) 2015 Institute of Pharmacology, Polish Academy of Sciences. Published by Elsevier Sp. z o.o. All rights reserved.