and at doses of 50 to 300 mg/day as an antiandrogen.

Uh I think that entire range is irl crimes

the more as some of the side effects may be related to the progestational overdosage rather than to the administered antiandrogenic activity. […] Adverse reactions like tiredness, lassitude, and increase in body weight are possibly due to the enormous overdose of progestational activity in the formula

Well that fuckin makes sense, and these studies are from the 1970s, ffs. Western medicine is a joke. What interested me here though

T decreased from ~431 ng/dL at baseline to ~149 ng/dL with CPA (–65%) for the 10 and 20 mg/day doses combined.

Seeing figures like this make me go Oh, well that's not like upwards of 90%! But as stated in the article E, even at like 4mg would offer a pretty good amount of suppression too though, these dorks are cypro only:

Fung and colleagues showed that the combination of either 25 or 50 mg/day CPA with a moderate dosage of oral estradiol (~3.5 mg/day) or transdermal estradiol (~3.5 mg/day gel or ~100 μg/day patch) resulted in equivalent and complete suppression of gonadal testosterone production (~95% suppression of testosterone levels) in transfeminine people (Fung, Hellstern-Layefsky, & Lega, 2017).

So CPA's not 100% effective on its own under 50mg, but more than like 10mg is overkill with estrogen:

Accordingly, Meyer et al. (2020) assessed a dosage of CPA in combination with estradiol in 155 transfeminine people and found no difference in testosterone levels with 10, 25, or 50 mg/day CPA; testosterone levels were strongly suppressed with all three doses (to about 15–20 ng/dL on average, or into the lower end of the normal female range). The estradiol forms and doses used in this study were oral estradiol valerate (median 6 mg/day, range 3–10 mg/day), transdermal estradiol gel (median 2.25 mg/day, range 1.5–6 mg/day), and transdermal estradiol patches (100 μg/day in all cases). Estradiol levels were about 100 pg/mL on average, with an interquartile range (i.e., difference between 75th and 25th percentiles) of about 100 pg/mL. This study demonstrates that, provided estradiol levels are adequate, no more than 10 mg/day CPA is needed to fully suppress testosterone levels in transfeminine people.

I think I'll wait to do 6mg though, I dunno:

Even doses of CPA lower than 5 mg/day (e.g., 2 mg/day) may be usefully effective for testosterone suppression if combined with sufficient levels of estradiol, although this has not been studied and remains to be validated. But there is certainly precedent for the notion when looking at studies with other progestogens.

I don't see a lot of support for lower than 10mg, Idk. I do wish this shit came in 10 or 20mg tabs instead of fucking 50.