"There were significantly more self-medicating individuals than controls in the mammoplasty group (11.5 vs. 6%, P < 0.05). The type of estrogen use did not affect the outcome. Compared with other antiandrogens, spironolactone use was significantly higher in those requesting mammoplasty (4.8 vs. 1.8%, P = 0.002)."
It could just be that Spiro is a less effective anti-androgen vs. others, androgen being a strong inhibitor of breast development or that self-medicators have a personality temperament that makes them more likely to seek breast augmentation and to self-medicate or that self-medicators happened to use Spiro more often. These are all associations and I'm afraid no cause and effect can be concluded from this.
The difference between anti-androgens was not even significant.
"With regard to the use of antiandrogens, overall there was no statistically significant difference in the use of antiandrogens between those requiring breast augmentation and controls."
On spironolactone and estrogen
Expert Opin Drug Saf. 2012 Sep;11(5):779-95.
"displaces estrogen from sex hormone-binding globulin (SHBG) and increases the peripheral conversion of testosterone to estrogen leading to elevated estradiol [12].Estradiol levels decrease and testosterone increase significantly 3 – 6 months after stopping spironolactone [12]."
Ann Intern Med. 1977 Oct;87(4):398-403.
"Peripheral blood levels of testosterone, estradiol, luteinizing hormone, and follicle-stimulating hormone and the metabolic clearance rates of testosterone and estradiol, as well as the peripheral conversion of testosterone into estradiol, were measured in 16 patients with hypertension. Six of these patients were treated with spironolactone and developed gynecomastia."
Hypertension is usually treated with lower doses of Spironolactone relative to what is prescribed to transwomen.
"blood estradiol levels in the spironolactone group (30 +/- 4 pg/ml) were significantly greater (P less than 0.01) than in the control group (13 +/- 2 pg/ml). These changes were primarily due to significant increases in the metabolic clearance rate of testosterone (P less than 0.02) and in the rate of peripheral conversion of testosterone into estradiol (P less than 0.001) in the spironolactone-treated group."
I wouldn't call the increase in estradiol levels phenomenal, LOL. An increase by 17 pg/ml is very small when one considers range in females during menstrual cycle to be 20-650 pg/ml.
Interestingly,
Clinical Pharmacology & Therapeutics
Volume 24, Issue 4, pages 465–473, October 1978
"To evaluate the long-term effects of spironolactone, 30 normal males were randomly divided into three groups(...)"
"The study was double blind and lasted 10 months."
(doses were typical of what is prescribed for transwomen)
"The concentrations of testosterone, estradiol, estriol, luteinizing hormone, follicle stimulating hormone, progesterone, and prolactin were also determined before treatment and at two-month intervals during treatment."
"Spironolactone induced no significant changes in the metabolic clearance of androstenedione or testosterone. Plasma concentrations of the various hormones did not change as a result of either spironolactone or the development of gynecomastia. Inhibition of testosterone synthesis or alteration in its metabolic clearance by spironolactone does not appear to be the cause of spironolactone-induced gynecomastia in man."
And,
J Clin Endocrinol Metab. 1977 Aug;45(2):255-60.
"One group of nine men took *mg daily for 4 weeks, none for 4 weeks, then *mg daily for 4 weeks."
"The serum concentrations of FSH, LH, testosterone and estradiol, however, did not change during either period, nor did the FSH and LH responses to synthetic gonadotropin-releasing hormone."
"Another group of 9 men took * mg of spironolactone daily for up to 24 weeks. During this time, 6 developed gynecomastia and 2 noted a decrease in libido." (dose was higher than typical for most transwomen)
"No change occurred in the mean serum concentrations of FSH, LH, testosterone or estradiol."
"We conclude that spironolactone-induced gynecomastia and occasional semen abnormalities do not appear to be due to changes in the serum concentrations of testosterone or estradiol. We hypothesize that these changes may be related to binding of canrenone to tissue androgen receptors."
From these studies alone, it appears that higher doses of spironolactone (typically comparable to what transwomen take) did not increase estradiol. Smaller doses (probably) in the other study resulted in a very small increase in estradiol levels.
Spironolactone appears to have a significant blocking effect of androgens at the receptor.
So, when authors state that
"it also has a significant estrogenic action at the doses used in transwomen." I strongly question this and the researchers' objectivity. The increase, if any, in E2, is too small to even make such a strong statement.
The authors of this study seem to have a bias, a negative opinion of high estrogen levels (due to ignorance) and seem to have an agenda, that of trying to discourage transwomen of self-medicating (or supplementing) by asserting that, if you do, too high estrogen levels can actually backfire and prevent optimal breast development by causing breasts to fuse too early which is a hypothesis invented by them, not based on any study. Could it be they are trying to regain control over their patients for research purposes or for personal purposes?
Too many other factors have been ignored in the discussion.
So when it is said...
"One can postulate that this could lead to an excessive estrogenic action and consequent poorer breast outcome by the same mechanism as that seen when patients self-medicate with estrogens."
Studies do not indicate that the addition of spironolactone leads to significantly higher levels of estradiol, if any. Self-medicators may seek breast augmentation, NOT because they took too much estrogen (and poorer breast growth outcome) but because the trait or motivation (wanting bigger breasts, their demands being higher) that led them to seek breast augmentation is the same trait/motivation that led them to self-medicate. This is why associations are weak in research because there are CONFOUNDING VARIABLES!
One wonders as well...how come pregnant women have increased breast growth when estrogen levels are VERY high?
Seeking mammoplasty is also not necessarily an indication of poorer breast growth outcome but perhaps more of individual expectations/ambitions and personality. Hence, it is an unreliable criteria for determining breast growth. Rather one should take measurements of breasts, determine degree of proportionality to body to determine whether breast growth outcome is poor or not. Also, time on HRT is an important factor.
In any case, jumping to conclusions is extremely difficult. One should be cautious.