Norethisterone made me sick for 4 days, so I quit.
Taking progesterone will lower testosterone levels in the short term. I had a blood test 2 days after finishing the usual 5 day course for one O.
Dr advised that he expects progesterone to reduce testosterone for a while. The test results confirmed this. I took another blood test when I had not taken progesterone for over a week and it had returned to within the healthy range. My Doc advised there are other drugs which reduced testosterone and this included treatments for male pattern baldness. When taking male pattern baldness medication testosterone reduces and returns to normally levels afterwards when stop taking the medication. I guess we just don't know if progesterone could affect testosterone levels adversely for long periods of time or permanently. I expect POIsers with causal factor being low testosterone could have a bad experience with the testosterone lowering effect progesterone can have, in my limited understanding.
You never know perhaps progesterone could have the side effect of preventing baldness. It would be good if my bald patch didn't get any bigger!
FB