ABSTRACT
Thyroid-stimulating hormone (TSH, thyrotropin) is a glycoprotein composed of two noncovalently linked subunits, desginated as the a and ~. TSH is structurally similar to other glycoprotein hormones including luteinizing hormone (LH, lutropin), follicle-stimulating hormone (FSH, follitropin), and human chorionic gonadotropin (hCG). While these hormones share a common a-subunit within species, the ~-subunit is unique and, when combined with an a-subunit, confers biologic specificity to the respective hormone. Both of the subunits of TSH are glycosylated with the a-subunit containing two and the ~subunit possessing one asparagine N-linked carbohydrate residues each (reviewed in Chapter 2).
