The exaggerated prolactin response to thyrotropin-releasing hormone and metoclopramide in 1,2-dibromo-3-chloropropane-induced azoospermia

Abstract

Twelve males with azoospermia secondary to exposure to the nematocide 1,2-dibromo-3-chloropropane were challenged to iv LRH (100 micrograms), TRH (200 micrograms), and metoclopramide (MET; 10 mg) administered 30 min apart. When compared to 24 male controls, both basal FSH and LH levels as well as peak gonadotropin responses to LRH were increased in the azoospermic group. The patients also had increased total estradiol (E2) and testosterone (T) as well as testosterone-binding globulins levels. Free T levels, however, were not significantly different from the controls. Basal PRL levels were similar in the two groups. However, the peak PRL responses to both TRH and MET were significantly increased in the azoospermia subjects (P < 0.001). In both groups, the PRL response to MET was greater than to TRH. In the individual control and azoospermic subjects, there was no correlation between the PRL response and E2, T, or the E2 to T ratio. However, a positive correlation did exist between testosterone-binding globulin levels and the PRL response to TRH and MET. Although the precise mechanism underlying the PRL hyperresponsiveness is unknown, it may be an estrogen-induced phenomenon.