BIOACTIVE FOLLICLE-STIMULATING-HORMONE

Specific and sensitive in vitro bioassays suitable for measurement of follicle-stimulating hormone (FSH) in small quantities of serum and urine have recently been validated. Comparisons of bioassay (B-FSH) potencies with immunoassay (I-FSH) estimates and chromatofocusing patterns have facilitated new discoveries regarding the regulation of FSH biosynthesis, storage, secretion, serum concentrations and target cell responsiveness, plasma clearance, and the significance of excreted forms. A review of recent studies reveals that luteinizing hormone and FSH, as well as B-FSH and I-FSH, appear to be differentially regulated by GnRH, GnRH agonists and antagonists, sex steroids and gonadal peptides in both sexes, with significant differences between the sexes. The results support the overall hypotheses that the quality as well as the quantity of FSH are significant contributors to target cell signal transduction and that distinct FSH isoforms with different functional capabilities influence the expression of acute (ovulation) and chronic reproductive events.