ABSTRACT
Using a variety of fractionation techniques, a number of isoforms of FSH from a wide range of species have been identified. As the isoform distribution is dramatically affected by neuraminidase treatment which specifically removes terminal sialic acid residues it would appear that hormone heterogeneity is largely due to its sialic acid content. Since the desialylated hormone is cleared more rapidly from the circulation than the native hormone, the various isoforms may have different biological activities in vivo. Examination of the immunological, in vitro bioactivity, and receptor-binding activity of these isoforms also shows differences indicating that the various isoforms may also differ in their receptor binding and subsequent biological activity.
