ABSTRACT
Follicle-stimulating hormone (FSH) is an essential factor for the regulation of reproductive functions. It belongs to the group of glycoprotein hormones - FSH, luteinizing hormone (LH), thyroid-stimulating hormone (TSH), and choriogonadotropin (CG) - which share a number of structural features. They are composed of two dissimilar, noncovalently complexed subunits, a and 13. Within a species, the a-subunit of these hormones is identical, having a chain length of 92 (human) or 96 amino acids (ovine, bovine, equine, and rat). 1.2 Two asparagine residues at positions 52 and 82 carry oligosaccharide chains of the N-linked complex typel (Figure 1). The l3-subunits, which are thought to determine the hormonespecific biological effects, differ between the various glycoprotein hormones on an intraspecies level, although considerable homology exists in some portions of the sequence. They comprise about 120 to 130 amino acids with asparagine-linked complex oligosaccharide chains at positions 7 and 24 for FSH. I The biological activity of glycoprotein hormones is bound to their integral structure. The individual subunits are biologically inactive.3
