I was told adding bioidentical micronized progesterone to my HRT of Lupron, Elestrin and Avodart after my orchiectomy will also have an anti androgenic effect to fight hair loss. I want to get some brands that I can bring up to my Endo when i see him on January 20th. I am VERY concerned about hair loss and have noticed some thinning at the hairline and I want to MAKE SURE i can AT LEAST stop it COLD, even reverse the thinning. I am getting an orchiectomy on Jan 11th but I have heard that hairloss can actually continue afterwards even taking Avodart daily. So I think since I am 21 I should be as aggressive with this as possible.

I was also told  :

"those with 19 or 20 carbon atoms are the 'bad' ones, which can actually have androgenic effects! The 'good" ones, with AA
effects, have 21 carbon atoms, like the bioidentical micronized progesterone."

So any that fit this category with the 21 carbon atoms would be very much appreciated.

I think your are barking up the wrong tree with the carbon atoms.  Estrogens have 18, Testosterone has 19, Progesterone has 21, and cholesterol (which is the precursor of all sex steriods) has 27.

I find it interesting that the enzyme aromatase can convert testosterone to estradiol by pulling off a side chain and reducing the number of carbon atoms by one.

Microgest and Prometrium are two brands of micronized progesterone.  I wouldn't recommend any progestin, which is not a true progeseterone. 

Sorry, as I already PM to the author of this topic upon his request, I lost the original source, but it was
either Wikipedia or some other scientifical or medical web site.
I found another (slight different one) source reporting still other numbers:

http://www.gynogab.com/2011/03/progesterone-vs-progestin-natural-vs.html

Please understand what organic chemistry is, you can't just compare two molecules simply by the number
of carbon atoms, it depends also on HOW they are linked.

The only thing which is clear is that there're both progestins with androgenic OR antiandrogenic properties.
Natural progesterone (bioidentical) has AA effect and IS good (even if doctors usually don't want to
prescribe it to us, go understand why...)

I'm getting Finasteride on prescription.  The primary effect is to combat hair loss, which has already gone too far in my case, but it also has feminising effects.  I'm prescribed the full dose, not the "cut a tablet in four" sometimes recommended to avoid diminished libido or erectile dysfunction.  In my case those aren't side effects - they are part of the intended effects.  I'm not prescribed progesterone but I'm taking Microgest anyway.