Hypogonadism in a Man With Cystic Fibrosis and an Unusually Low Serum Testosterone: A Cautionary Tale

Abstract

Background/ObjectiveMen with cystic fibrosis (CF) have a high prevalence of low testosterone levels. A recent retrospective study demonstrated a quarter of a cohort of men with CF had serum testosterone levels below 300 ng/dL.1 The evaluation of hypogonadism is of increasing clinical importance in order to prevent unfavorable outcomes. Herein we present a 31-year-old man with CF and a relatively low serum testosterone value who was found to have an additional unsuspected cause of male hypogonadism. Case ReportThe patient was a 31-year-old man with history of CF who was referred to endocrinology clinic for the evaluation of hypogonadism. Serum testing revealed a total testosterone of 175 ng/mL (296-1377), luteinizing hormone 2.8 mIU/mL (1.2-8.6), and a prolactin of 341 ng/mL (3-13). A brain magnetic resonance imaging was obtained, which revealed a 1 cm hypoenhancing left sellar lesion. He was started on cabergoline. His testosterone increased to 707 ng/dL after a year on cabergoline treatment. His prolactin decreased to 12 ng/mL after a year of treatment. The pituitary adenoma decreased 50% in size 2 years after cabergoline was initiated. DiscussionThe most common etiologies of CF are recurrent infections, chronic inflammation, and glucocorticoid administration, which lead to both hypothalamic-pituitary dysregulation and primary hypogonadism. However, other less common causes of hypogonadism can also be found in CF. ConclusionWe suggest that all men with cystic fibrosis whose serum testosterone is < 300 ng/dL undergo additional studies to identify any coexisting reasons, other than sequelae from cystic fibrosis, for low testosterone levels.