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

BACKGROUND/OBJECTIVE: Men 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. 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 REPORT

The 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.

DISCUSSION

The 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.

CONCLUSION

We suggest that all men with cystic fibrosis found to have hypogonadism undergo additional evaluation for causes of hypogonadism prior to treatment with testosterone.