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
Anti-Müllerian hormone testis suppresses Müllerian development only on its own side. In humans, this action takes place during the first 8 weeks of gestation. If no hormone is produced from the gonads, the Müllerian ducts automatically develop, while the Wolffian ducts, which are responsible for male reproductive parts, automatically die. Amounts of AMH that are measurable in the blood vary by age and sex. AMH works by interacting with specific receptors on the surfaces of the cells of target tissues (anti-Müllerian hormone receptors). The best-known and most specific effect, mediated through the AMH type II receptors, includes programmed cell death (apoptosis) of