Lack of nocturnal prolactin increase in patients with hypogonadotropic hypogonadism

The circadian prolactin rhythm was studied in a group of 16 male adult volunteers: 10 healthy subjects and 6 patients affected by isolated hypogonadotropic hypogonadism (IHH). A significant nycto-hemeral prolactin rhythm (p = 0.0003, according to cosinor method) is detected in healthy subjects, but not in patients with IHH. In view of these results we may deem that the absence of nycto-hemeral variations of serum prolactin in subjects with IHH could be caused by failure of LH and FSH release.