number of papers where the relationship between gynecomastia and progesterone is mentioned. As Big Cat succinctly put it,
"What is being said is basically that progesterone can only cause or aggravate gyno in the presence of circulating estrogen."
Just a couple of quotes from studies I pulled up on medline:
"Plasma progesterone was raised in 36 of 50 (72%) men with liver disease compared with 20 healthy male control subjects. Plasma progesterone was significantly higher in men with non-alcoholic cirrhosis with gynaecomastia than those without, but no similar relationship was found in men with alcoholic fatty change and alcoholic cirrhosis. Hyperprolactinaemia was found in 14% of men with liver disease but levels were unrelated to the presence of gynaecomastia.. Increased circulating levels of progesterone and prolactin alone do not explain the development of gynaecomastia in patients with liver disease, but progesterone may be an additional factor acting in association with the known disturbances of other sex steroids. (1)
Progesterone enhances estrogen's stimulation of mammary gland growth, and our findings suggest that progesterone may play a role in the gynecomastia that occurs in men with hyperthyroidism. (2)
This is all we are saying: progesterone/progestins themselves are not capable of causing gyno (study 1), but enhance the action of estrogen, which is typically elevated in hyperthyroidism (study 2).
"True gynecomastia is a condition in which there is an enlargement of the male breast due to an increase in ductal tissue and periductal stroma.[13]"
http://www.medscape.com/viewarticle....2/7002/7001/-1
Estrogen receptor knockout mice manifest significantly impaired ductal development, implying that estrogen is key to ductal development, and by definition (see phrase in quotes above) gynecomastia.
I've cited these references time and time again. This is truly flogging a dead horse. If others wish to continue the discussion please do so. I'm bowing out as everything that can be said has been said many times over.
(1) Gut. 1982 Apr;23(4):276-9.
Progesterone, prolactin, and gynaecomastia in men with liver disease.
Farthing MJ, Green JR, Edwards CR, Dawson AM.
(2) J Clin Endocrinol Metab. 1988 Jan;66(1):230-2.
High serum progesterone in hyperthyroid men with Graves' disease.
Nomura K, Suzuki H, Saji M, Horiba N, Ujihara M, Tsushima T, Demura H, Shizume K.
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