Quote from: HughE on April 05, 2016, 01:17:03 PM
Aside from assisting the maturation of milk ducts
* Volume 18a of Elsevier's New Comprehensive
Biochemistry, Titled 'Hormones and Their Actions, Part I', editors BA
Cooke, RJB King and HJ van der Molen. Published 1988. ISBN
"Progesterone also acts synergistically with estrogen in the normal
development of the breast. Estrogen stimulates cell mitosis and growth
of the ductal system, while
lobular development and differentiation is
dependent on progesterone."
* J Mammary Gland Biol Neoplasia 1999
"Progesterone was identified as a mammogenic hormone several years ago
but until now its role has been obscure. Recently the role of
progesterone signaling in mammary development is becoming more clear."
"The most significant observations to emerge from these studies are
(1) progesterone receptors are essential for lobuloalveolar [but
not ductal] morphogenesis."
* Ann Endocrinol (Paris) 1986;47(3):179-87
"adequate cell differentiation can be obtained with the successive
and synergistic action of estradiol (E2) and progesterone (P),
essentially because the progesterone receptor (PR) synthesis
implicates the previous action of E2 via its E2 receptor (ER). In
normal breast, E2 stimulates the growth of the ductal system whereas
the development of acini depends on P secretion."
* De Groot LJ, Beck-Peccoz P, Chrousos G, et al., editors.
South Dartmouth (MA):
MDText.com, Inc.; 2000-.
Gynecomastia: Etiology, Diagnosis, and Treatment
Ronald S. Swerdloff, M.D.
"Estrogen and progesterone act in an integrative fashion to stimulate
normal adult female breast development. Estrogen, acting through its
ER a receptor, promotes duct growth, while progesterone, also acting
through its receptor (PR), supports alveolar development (15)."
* Steroids. 2004 Mar;69(3):145-59
"(...) The importance of the sex steroid hormones 17beta-estradiol
and progesterone for normal development of the mammary gland was
recognized several decades ago and has been unequivocally confirmed
since."
"(...) the hormones required for duct growth are estrogen,
somatotropin (STH), and adrenal corticoid. If P and prolactin (PRL)
are added to this combination, lobulo-alveolar growth is stimulated
[2]."
"(...)The biological responses of the mammary gland to P have
been intensively studied by many research groups [19,20]."
"(...) Data obtained with ER-KO and PR-KO models confirm
that E mediated signalling via ER is essential for ductal
morphogenesis, while P signalling via PR is critical for
lobulo-alveolar development. P is required for the transition
from ductal to lobulo-alveolar morphology. However,
it should be noticed that under normal physiological conditions,
E2 indirectly stimulates lobulo-alveolar architecture
formation too because it can also induce mammary PR expression via ER
[22]."
* Gynecology Obstetrics Department, Sénologie/Mastology – Pr Claude Colin
Hormone Dependence of the mammary tissue
"(...)Physiological thelarche only begins with the progressive
secretion of estrogens long before the first periods (menarche, at an
average of 13) and thus before any substantial progesterone
secretion. We then observe lengthening and ramification of the milk
ducts, as well as an increase in supporting connective tissue under
the influence of increased estrogen.
Lobulo-alveolar mammary development takes place after menarche, to
the benefit of ovulatory cycles accompanied by progesterone
secretion."
* Breast Carcinogenesis—Can the Examination of Ductal Fluid Enhance Our
Understanding? January 2005, Volume 32, Number 1
"Estrogen is responsible for the elongation of breast ducts and
thickening of the epithelium that occurs in puberty (Rosen, 2001).
Differentiation of the lobuloalveolar units occurs during puberty,
with insulin, progesterone, and growth hormone contributing to the
process (McCarty & Tucker, 1992; Rosen). These changes continue
through menstrual cycles, pregnancy, lactation, and menopause."
* Climacteric. 2013 Aug;16 Suppl 1:69-78.
"Once a pregnancy occurs, progesterone
is necessary for the full differentiation of breast tissue that
occurs in preparation for lactation. In the mammary gland,
progesterone acts synergistically with estrogen to transform
the terminal end buds into differentiated lobules necessary for
milk secretion 4 . »
* Breast Cancer Research and Treatment
October 1986, Volume 8, Issue 3, pp 179-188
"In normal breast, estrogen stimulates growth of the ductal system, while lobular development depends on progesterone. Thus, estrogen and progesterone, when secreted in an adequate balance, permit the complete and proper development of the mammary gland. »
Quote from: HughE on April 05, 2016, 01:17:03 PM
It also has an antiandrogenic effect, because it slows down the rate of testosterone to DHT conversion by tying up the enzyme 5-alpha reductase
The only study to have shown this with progesterone to any significant degree was using very high levels (supraphysiological) of progesterone in-vitro, if I recall correctly. So, at therapeutic doses, I doubt it will have any significant effect or at the very least, we cannot say anything with certainty.