What is "nestorone"

Segesterone acetate ( USAN)1 (brand name Nestorone; former developmental code names ST-1435, AC-6844, CS-0411), known more commonly simply as nestorone (or nestoron) and also known as elcometrine, is a steroidal progestin of the 19-norprogesterone group which is used as a hormonal contraceptive in several South American countries. Nestorone is the acetate ester of segesterone, which was never marketed, but is an active metabolite of nestorone. Nestorone is only weakly active orally, and is instead given as a subcutaneous implant. It is more than 100-fold times as potent when delivered subcutaneously relative to orally.

Nestorone acts primarily as a high- affinity agonist of the progesterone receptor. It lacks significant affinity for the androgen receptor, and accordingly, does not produce any androgenic or anabolic effects. It does not bind to the estrogen receptor either. Nestorone does however have some affinity for the glucocorticoid receptor, where it appears to act as an agonist, but it does not appear to produce any glucocorticoid side effects unless used at high doses. It does not bind to the mineralocorticoid receptor. Nestorone does not bind to sex hormone-binding globulin, and is instead bound to serum albumin.