Using a recently developed granulosa cell aromatase bioassy (GAB), we measured serum bioactive follicle-stimulating hormone (bio-FSH) levels in 5 normal men after administration of a potent GnRH antagonist. Although only minimal suppression of immunoreactive FSH (immuno-FSH) was detected during administration of 20 mg of the antagonist, ([N-Ac-D-Nal(2)1D-pCl-Phe2 D-Trp3D-h(Arg(Et2)6 D-Ala10]GnRH, pronounced inhibition (79 to89%) of bio-FSH levels occurred. Concomitantly, the ratio of bio- to immuno-FSH levels dramatically decreased within 6 h after antagonist administration. These data reinforce earlier expectations that GnRH antagonists might be potential male contraceptives and provide the first report of changes in circulating bio- to immuno-FSH levels. The GAB assay will facilitate future studies on the biochemical mechanisms by which GnRH antagonists induce changes in the bioactivity of circulating FSH.
All Science Journal Classification (ASJC) codes
- Endocrinology, Diabetes and Metabolism
- Clinical Biochemistry
- Biochemistry, medical