Norethindrone (Ethynyl-13C2) is the 13C labeled compound of Norethindrone. Norethindrone has a CAS number of 68-22-4. Norethindrone is a synthetic progestational hormone with actions similar to those of PROGESTERONE but functioning as a more potent inhibitor of ovulation. It has weak estrogenic and androgenic properties. The hormone has been used in treating amenorrhea, functional uterine bleeding, endometriosis, and for contraception.