Endocrine assessment of impotence--pitfalls of measuring serum testosterone without sex-hormone-binding globulin.

The pitfalls of measuring only total serum testosterone are illustrated by a 52 year old man whose hyperprolactinaemia was associated with normal total serum testosterone but a raised sex-hormone-binding globulin, giving a low free testosterone. Prolactin suppression with bromocriptine normalized sex-hormone-binding globulin and free testosterone, and restored potency and energy after 30 years of impotence and tiredness.