Research is a never ending study. Only the uneducated claim science is settled. Keep in mind, medicine is science. I swore at Harry Benjamin and his Standards of Care the first time I read about his diagnoses of transgender. Truth be known, I wished for...,

I've parsed both articles and if one wants to read them as they were written then please go to the web page. However be advised I am not an outside observer as I am actively engaged. Thus I am kinda prejudice as to if it works.

Benefits and Negative effects of using Progesteron
https://academic.oup.com/jcem/article/104/4/1181/5270376 (this was a medical study)
Progesterone Is Important for Transgender Women’s Therapy—Applying Evidence for the Benefits of Progesterone in Ciswomen
Oral Micronized Progesterone’s Benefits for Transgender Women (I strongly disagree it should not be taken orally unless one wants to kill themselves)
More rapid feminization
Progesterone suppression of gonadal androgen production
Progesterone plus E2 leads to optimal breast maturation and size (This is why I’m dancing naked around a cactus in the full moon giving thanks to the Breast Fairy Queen. It’s working. I'm also still massaging the breasts with the change in hormones)
Progesterone improves cardiovascular physiology

https://queerdoc.com/blog/progesterone/ (Not exactly a medical research paper)
A study done in the 1990s, called the Women’s Health Initiative1, raised some concerns that supplemental progesterone increased the rates of cardiac events, strokes, pulmonary emboli, and invasive breast cancers in post-menopausal cis women. An entirely different progesterone (who knew there were so many different kinds) and used only genetic women in their research
For MtF women progesterone brings about more developed feminization
Helps create larger more developed breasts
Reduces testosterone
Eestrogen and progesterone work hand-in-hand (and some times in opposition) to bring about these health benefits.
We know that progesterone is needed for the later stages of breast development in cis women (Tanner 4-5
SYNTHETIC progestins cause increases in strokes, heart problems, and blood clots, BUT micronized progesterone, which is BIOIDENTICAL, does not have these effects

Barb, back to my studies.It should be taken annus, to bypass the liver, which is a disgusting job, but we’re women and we can handle the dirty jobs men won’t touch.

Keep in mind testosterone is produced in genetic women. Zero testosterone will result in tiredness, lack of energy, lethargic. Don't shut it all down. I did for two months to kick start the estrogen. Did it on purpose and with medical guidance. Please be very careful with your body. It was assigned to you in trust. "IF" one is MtF and taking spirolactone, I strongly advise them to watch this video. Besides keeping breast development from happening there are other negatives associated with it. It is a drug I wish had never been suggested for MtF care. Damn you Harry Benjamin.
https://www.youtube.com/watch?v=LX8AdkL7u0s

Please to God do NOT go off on a tangent and change your hormones without consulting your doctor. Be very careful what one wishes for as Transgender Care is not approved by any medical board. There are no, zero medicines which are approved for transgender. Everything prescribed is done off label by one's doctor. If you are a vet check around if you aren't receiving care. Amarillo washed me out of TG care. OKC doesn't have any reservations except the progesterone. I was already on it and my Endo said, "You've studied the risks, I'll allow it but I won't prescribe it for anyone else." My psychologist and I both laughed when I told her. "You're on the outside looking in. I'm on the inside looking out. I have the advantage."
Hugs People, Gear Up!
Barb
Life is too short to take seriously. Have fun with it if possible.