ASYMPTOMATIC BIG HYPERPROLACTINEMIA IN 2 MEN WITH PITUITARY-ADENOMAS

'Big' and 'big-big' hyperprolactinemia, the presence of increased seru m concentrations of high molecular weight (50-60 and 150kDa respective ly) prolactin forms, has mostly been reported in women with idiopathic hyperprolactinemia and normal hypothalamic-pituitary ovarian axis fun ction. It has been suggested that both 'big' and 'big-big' prolactin s pecies are biologically less active than the 22 kDa form predominating in normal individuals. We report the cases of two men with pituitary adenomas who were secreting significant amounts of 'big' (50-60kDa) pr olactin documented by Sephadex G-100 column chromatography. Both patie nts reported normal sexual function despite high prolactin levels. Res ults of nocturnal rigidity and tumescence testing were normal, confirm ing that significant hyperprolactinemia was not interfering with eithe r patient's sexual function. 'Big' hyperprolactinemia should thus be s uspected even in male patients with prolactin-secreting pituitary aden omas who maintain adequate sexual function in the presence of high pro lactin levels.