The prolactin response to TRH and domperidone does not differentiate male hypothalamic hypogonadism and constitutional delay of puberty.

In order to test whether prolactin response to challenge with TRH and domperidone, dopamine receptor antagonist, is diagnostic for idiopathic hypothalamic hypogonadism (IHH) we studied 8 normal controls, 9 subjects with delayed sexual development and 6 patients with IHH. TRH test (200 micrograms i.v. bolus) and domperidone (10 mg i.v. bolus) were given on two different days. Prolactin (RIA-Biodata) was determined in blood samples during the test. The basal value of prolactin in subjects with delayed puberty and healthy controls did not differ from basal values of prolactin in patients with IHH. The peak elevation of prolactin after TRH in subjects with delayed puberty and healthy controls did not differ from that in patients with IHH. After successful treatment of one patient with IHH (Kallmann's syndrome) with pulsatile s.c. LHRH we did not find any change in the response of prolactin to TRH challenge after 1, 3 and 6 months of treatment, while prolactin response to domperidone increased. Prolactin responses to TRH and domperidone are not differential for the early diagnosis of IHH. Successful treatment of a patient with IHH did not change the response of prolactin to TRH, but increased prolactin response to domperidone possibly due to altered steroid milieu.