More complex protein hormones have carbohydrate side chains and are called glycoprotein hormones. Hormones in this class are Follicle-stimulating hormone (FSH; follitropin), Luteinizing hormone (LH), Thyroid-stimulating hormone (TSH; thyrotropin) and human chorionic gonadotropin (hCG). The alpha subunit of glycoprotein hormones is a 92 aa peptide and serves as the alpha subunit for FSH, LH, hCG and TSH (Fiddes JC and Goodman HM, 1981). The beta subunits for these hormones are unique and confer biological specificity to them. These two subunits combine via disulphide bonding to produce the mature glycoprotein hormone dimer.