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
Growth hormone–releasing hormone Growth hormone–releasing hormone Growth hormone–releasing hormone (GHRH), also known as somatocrinin or by several other names in its endogenous forms and as somatorelin (INN) in its pharmaceutical form, is a releasing hormone of growth hormone (GH). It is a 44-amino acid peptide hormone produced in the arcuate nucleus of the hypothalamus. GHRH first appears in the human hypothalamus between 18 and 29 weeks of gestation, which corresponds to the start of production of growth hormone and other somatotropes in fetuses. GHRH is released from neurosecretory nerve terminals of these arcuate neurons, and is carried by the hypothalamo-hypophyseal portal system to