Comparison of pituitary response to regular GnRH, analogue (D-TRP6) and placebo

Pituitary response to synthetic regular GnRH, to a potent analogue (D-TRp6) and to placebo were compared in ten azoospermic males. FSH and LH were measured prior to and at given intervals following administration of each substance. In addition, plasma levels of testosterone and prolactin were measured. There was no significant difference in the magnitude of FSH and LH release following injection of their the regular or the analogue form of GnRH. However, plasma gonadotrophins remained elevated for significantly longer time periods following the administration of the analogue GnRH. In those patients in whom LH levels remained elevated for at least 24 hours the observation of elevated testosterone levels permitted the inference of adequate biological activity of endogenously produced LH. Patients who did not respond to the regular GnRH were also non-responsive to D-TRp6 GnRH. A surprising finding ws elevated prolactin levels 4-6 hours following GnRH administration. Placebo had no influence on gonadotrophins, testosterone and prolactin.