Progesterone does seem to help with my nipples. Also,
From a report coming from a Clinic in Vancouver where hundreds of transsexuals have been treated since 1986.
"Progesterone appears to be necessary for maturation of the areolae
and nipples to Tanner stage 5."
Current Concepts in Transgender Identity, by Dallas Denny, 1998
« Progesterone activity also allows the full maturity of the breast and nipple development (maturity to Tanner 5 stage requires progesterone (unpublished Prior, 1989))"
Progesterone can, however oppose estrogen and cause breast shrinkage.
Fertil Steril. 1995 Apr;63(4):785-91.
"Increased E2 concentration increases the number of cycling epithelial cells. Increased P concentration significantly decreases the number of cycling epithelial cells."
"Exposure to P for 10 to 13 days reduces E2-induced proliferation of normal breast epithelial cells in vivo."
Fertil Steril. 1998 May;69(5):963-9.
"Increasing the estradiol concentration enhanced the number of cycling epithelial cells, whereas increasing the progesterone concentration significantly limited the number of cycling epithelial cells."
"Exposure to progesterone for 14 days reduced the estradiol-induced proliferation of normal breast epithelial cells in vivo."
