This editorial refers to combination oestrogen-progestin contraceptives but in the concluding sentences implies that levonorgestrel and norethisterone are types of progesterone. Stephenson in her letter refers to the etonogestrel containing implant as a progesterone implant.Progesterone appears to have been used as a synonym for progestin. The British Pharmacopeia lists the action and use of progesterone and progestins such as levonorgestrel and norethisterone as progestogen. There appears to be a lot of confusion around the group name for progestational
agents. In 1976 Dalton argued that progesterone should not be confused with or considered the same as progestins (synthetic progestogens). Yet in 2009 it appears they are still being confused.
The confusion possibly arises because of the use of oestrogen and progesterone to represent the female sex hormones. Oestrogen is a generic term for oestrogenic agent, and there are three primary oestrogens in the
human body; oestrone (E1), oestradiol (E2), and oestriol (E3). On the other hand progestogen is the generic term for a progestational agent and progesterone (P4) is a single chemical entity and the primary progestogenic hormone synthesised by the human body. The termprogestin can be used to refer to synthetic progestational agents.
It appears that the difference between progesterone, progestogens, and progestins is still not appreciated. Confusion associated with interpreting research findings with regard to progesterone and progestins would be reduced if a consistent name, other than progesterone, was used to represent synthetic progestogens.
Synthetic progestins are molecularly different from natural progesterone and therefore do not metabolize to the same compounds as natural progesterone. They do not show benefits for cognitive or anti-anxiety function. In fact, they have not been found to have any of progesterone’s neuroprotective properties. The progestin that has been the most extensively studied and which is commonly used in synthetic hormone replacement therapy, MPA (medroxyprogesterone acetate), has been found to have negative effects on the nervous system and even reduces the beneficial effects of estrogen.
