Breast development extension adrenocorticotropic hormone (ACTH)), and thyroid hormones such as thyroxine (and by extension thyroid-stimulating hormone (TSH) and thyrotropin-releasing hormone (TRH)) also play permissive but less well-understood/poorly-characterized roles in breast development during both puberty and pregnancy, and are required for full functional development. Leptin has also been found to be an important factor in mammary gland development, and has been found to promote mammary epithelial cell proliferation. In contrast to the female-associated sex hormones, estrogen and progesterone, the male-associated sex hormones, the androgens, such as testosterone and dihydrotestosterone (DHT), powerfully suppress the action of estrogen in the breasts. At least one
Transgender hormone therapy (male-to-female) cases of prostate cancer in transgender women have been reported in the literature. As such, and in accordance with the fact that androgens are responsible for the development of prostate cancer, HRT appears to be highly protective against prostate cancer in transgender women. The risks of hormone-sensitive cancers in transgender women have been reviewed. Estrogens and progestogens can cause prolactinomas, which are prolactin-secreting tumors of the pituitary gland. Milk discharge from the nipples can be a sign of elevated prolactin levels. If a prolactinoma becomes large enough, it can cause visual changes (especially decreased peripheral vision), headaches, depression or other