Epidemiology, diagnosis, and treatment of male hypogonadotropic hypogonadism.

Hypogonadotropic hypogonadism (HH), or secondary hypogonadism, is a clinical condition due to an impairment of the pituitary function, characterized by low testosterone plasma levels associated with normal or low FSH and LH plasma levels. An impairment of gonadotropin secretion and, therefore, a reduced efficiency of spermatogenesis was reported to be frequently associated to conditions different from the classical causes of secondary hypogonadism. These conditions (metabolic, endocrine and eating disorders, physical exercise etc.) have been associated with a non-classical form of HH that could be called "functional" HH (FHH). FHH differs from the classical one by the evidence that gonadotropin levels are in the low-normal range, but are inadequate for the testosterone levels, that often are also in the low-normal range. This commentary aims at reviewing knowledge on the forms of male HH in order to indicate and discuss clinical context, diagnostic and therapeutic approach in the less known non-classical form, i.e. FHH.