Progesterone USP is both a pro-hormone and a neurosteroid [1]. The science literature commonly confuses Progesterone USP with various "progestins" (xeno-hormones), so there is much confusion on the effects of this substance vs the fakes.
> I seriously think there should be some inquiry into whether it is a driver for the epidemic of post-transition MTF trans suicides
At one point I made a progesterone supplement, which I sold on Amazon - topical progesterone formulas are grandfathered as non-prescription because they are safe, and because the substance was available before the food & drug act was passed. My best customer was "Billie", whom I never met, but who I'm certain was MTF. SHe emailed me recently when she ran out of her last purchase - I told her what to buy instead.
MTF probably usually do poorly post-transition because they only supplement with "the heart attack hormone"/"The Cancer Hormone" - Estrogen. Progesterone USP is essential for balancing the toxic effects of any kind of estrogen/xeno-estrogen. Fertile women are protected from their estrogen load because their bodies produce large amounts of Progesterone during the second half of the cycle.
[1] https://www.ncbi.nlm.nih.gov/pubmed/11108866
edit: gender pronouns