(bā'tă hyū'măn kōr'ē-on'ik gō-nad'ō-trō'pin) A 145-amino acid subunit unique to HCG, which has the same α-chain as FSH, LH, and TSH. Pregnancy tests specific for β-HCG are more sensitive because there is no confusion with other gonadotropins secreted by the pituitary.