High levels of estrogen inhibit lactation.
Estrogen levels also drop at delivery and remain low for the first several months of breastfeeding.[SUP]
[3][/SUP] Breastfeeding mothers should avoid estrogen-based birth control methods, as a spike in estrogen levels may reduce a mother's milk supply.
Progestogens in turn are precursors to all other steroids, including the estrogens, androgens, mineralocorticoids, and glucocorticoids. Thus, all tissues producing steroids, such as the adrenals, ovaries, and testes,prostate must be capable of producing progestogens.
One of the main regulators of the production of prolactin from the pituitary gland is the hormone called dopamine, which is produced by the
hypothalamus, the part of the brain directly above the pituitary gland. Dopamine restrains prolactin production, so the more dopamine there is, the less prolactin is released. Prolactin itself enhances the secretion of dopamine, so this creates a negative feedback loop.In humans, prolactin is produced both in the front portion of the
pituitary gland (anterior pituitary gland) and in a range of sites elsewhere in the body.
Lactotroph cells in the pituitary gland produce prolactin, where it is stored in small containers called vesicles. Prolactin is released into the bloodstream by a process called exocytosis. Human prolactin is also produced in the uterus, immune cells, brain, breasts, prostate, skin and
adipose tissue.
High levels of estrogen inhibit lactation
http://en.wikipedia.org/wiki/Prolactin