A team of scientists working at the University of Pennsylvania have discovered PGD2 plays a significant role in typical MPB hair loss as well. The 2012 research paper indicates a causal link between elevated levels of localized prostaglandin D2 and hair loss. Applied topically, the research found PGD2 prevents hair growth, and mice that were genetically inclined to produce higher levels of PGD2 had inhibited hair growth. The research also found PGD2 levels were much higher in balding scalp tissue than nonbalding scalp tissue. The paper suggested one of the receptors involved in production of PGD2, GPR44, would therefore be a therapeutic targets for androgenic alopecia in both men and women with hair loss and thinning.
Progestogens The discovery that ethinyl substitution leads to oral potency led to the preparation of ethisterone, an orally active derivative of testosterone. In 1951, it was found that removal of the carbon-19 from ethisterone to form norethindrone did not destroy the oral activity and, most importantly, changed the major hormonal effect from that of an androgen to that of a progestogen. Accordingly, the progestational derivatives of testosterone were designated 19-nortestosterones. The androgenic properties of these compounds, however, were not completely eliminated, and minimal anabolic and androgenic activity remains. Examples of this class of progestogens include norethindrone, norethynodrel, ethynodiol diacetate, and some other related compounds not used in the United States. The second group of 19-nor compounds are gonanes, which have an 18-ethyl instead of an 18-methyl group. They include racemic norgestrel, levonorgestrel, and three newer compounds: gestodene, desogestrel (a pro-drug that must be converted to 3-ketodesogestrel to be biologically active) and norgestimate, which is the 17-acetyl-3-oxime derivative of norgestrel, into which it is rapidly metabolized.