Delayed diagnosis of psychological erectile dysfunction because of the presence of macroprolactinemia.

Idiopathic hyperprolactinemia can be found in men with either normal or low serum testosterone (T) levels. The explanation for the differing effects on T of similar PRL levels has not been found. Macroprolactinemia, as a clinical entity, has been reported mostly in women. These macromolecules are biologically less active and/or are transported less easily across the capillary bed than the 22-kDa molecules. Therefore, women with elevated PRL levels retain normal menses and fertility. We studied six men, aged 28-53 yr (mean, 45 yr), in whom hyperprolactinemia was initially considered to be the cause of their erectile dysfunction. PRL levels ranged from 25-92 ng/mL (normal, 2-15 ng/mL), but T and gonadotropin levels were normal, suggesting that PRL was not disrupting gonadotropin and gonadal steroid function. The results of magnetic resonance imaging studies of the pituitary gland were normal. Separation by Sephadex G-100 column chromatography showed a predominance (85-90%) of big (60 kDa) and big big ( > 150 kDa) PRL, in contrast to the predominance of 22-kDa PRL in normal subjects. Nocturnal tumescence testing was normal, supporting the diagnosis of psychogenic impotence in these subjects, and potency returned after counseling. Hence, the biologically inactive macroprolactinemia did not cause any organic derangement in erectile function. It further obscured and delayed the appropriate diagnosis and treatment of these individuals.