I believe that Progesterone levels could be playing a large role in PSSD.
I'll begin with some studies:
Effects of progesterone on the sexual behavior of castrated, testosterone-treated male cynomolgus monkeys (Macaca fascicularis).
https://www.ncbi.nlm.nih.gov/pubmed/9226343
The following study is really exciting because it ties Estradiol (E2) to Progesterone (PROG) in a way that I haven't seen anyone do before. If this is the case - follow my logic: Increased PROG could decrease E2 binding in the POA. First of all, this could explain why E2 treatment helps with PSSD, and could explain how high PROG levels in PSSD sufferers could be giving symptoms that are reversed by E2 in rats. Note also that E2 plays a big role in SERT expression. Should this be the case, lowering E2 in the POA (which is heavily tied to sex) could decrease SERT expression. As I've shown before, this could explain 5-HT1A AR desensitization, and explain why 5-HT1A ARs un-couple from GIRK channels - leading to increased 5-HT levels.P treatment, which resulted in high plasma P levels (about 44 ng/ml), produced decrements in measures of male sexual behavior and motivation...P did not decrease plasma T levels or change them in any way (about 850 ng/100 ml throughout)
This also tells you that your urologists and endocrinologists have been lying to you. They often state that if Testosterone levels aren't impacted that there can be no hormonal change that is causing your ED. This is false and shown by the above study and the one below. PROG can decrease sex drive without touching T levels. So you can have high T, but low drive. In fact, this is how they currently treat sex offenders - with Progesterone analogs.
Progesterone decreases mating and estradiol uptake in preoptic areas of male monkeys.
https://www.ncbi.nlm.nih.gov/pubmed/11790421
Synthetic progestins such as medroxyprogesterone acetate (MPA) are used widely in the treatment of male sex offenders. In male cynomolgus monkeys (Macaca fascicularis) treated with testosterone (T), both MPA and progesterone (P) had comparable inhibitory effects on male sexual motivation and behavior. To determine if P, like MPA, decreases endogenous T levels, plasma T and P levels were analyzed in weekly blood samples (N=186) from eight intact males, each paired with a sexually receptive female before, during, and after treatment with subcutaneous Silastic P implants (336 behavior tests). P treatment decreased sexual activity but not plasma T levels.
P, unlike MPA, did not affect the nuclear uptake of [3H]androgens by brain, but reduced by 80% the nuclear accumulation of [3H]E(2) in tissue samples containing preoptic area