Absence of hypogonadism in a male patient with a giant prolactinoma: a clinical paradox.

Background: Impotence and decreased libido are the cardinal features of prolactinomas in males. We describe the unusual clinical, pathological and biochemical features in a male patient with a giant prolactinoma and normal gonadal function.

Case Report: A 57 year-old man presented with visual symptoms related to a 30x25x60mm tumor of the sella and skull base. Biopsy revealed a pituitary adenoma and subsequent hormone profiles demonstrated grossly elevated serum prolactin (131,412ng/ml), LH at the upper limit of normal and normal testosterone. The patient had no symptoms of decreased libido or impotence related to this giant prolactinoma. Immunohistochemistry revealed a tumor that was positive for prolactin, alpha-subunit and LH. Cabergoline greatly reduced prolactin levels but these remained above normal. LH, testosterone and alpha-subunit levels were decreased in parallel. Loss of libido and impotence became apparent when testosterone fell below normal, a situation that resolved with further cabergoline treatment and prolactin inhibition and testosterone therapy.

Conclusions: Sexual dysfunction is a hallmark of prolactinomas in males. Tumors that co-secrete prolactin and LH are extremely rare and this is the first such case reported in an adult male. In this case, normal testosterone was maintained by intact LH levels even in the face of the highest prolactin level reported to date.