Encyclopedia of Health and Medicine

prolactin 157
See also ANDROGENS; BREAST HEALTH; ESTROGENS.
prolactin A peptide HORMONE the anterior lobe of
the PITUITARY GLAND synthesizes and secretes in
response to the HYPOTHALAMUS’s release of
GONADOTROPIN-RELEASING HORMONE (GNRH). THYROID-
RELEASING HORMONE (TRH) also stimulates prolactin
production. Prolactin is biochemically similar to
GROWTH HORMONE (GH). The primary function of
prolactin is to stimulate BREAST development and
milk production in women who are BREASTFEEDING.
Prolactin also appears to play a role in certain
immune responses. Other cells throughout the
body also synthesize and secrete prolactin, which
researchers believe is to enhance prolactin’s
immune functions. High levels of ESTROGENS in the
BLOOD, such as occur near the end of PREGNANCY,
increase prolactin secretion. DOPAMINE, a peptide
hormone the hypothalamus secretes, signals the
pituitary gland to stop secreting prolactin. Pituitary
ADENOMA (a noncancerous tumor) can cause
excessive prolactin secretion, resulting in galactorrhea
(abnormal milk production) in men as well
as women.
For further discussion of prolactin within the
context of the endocrine system’s structure and
function please see the overview section “The
Endocrine System.”
See also ADRENOCORTICOTROPIN HORMONE (ACTH);
ANTIDIURETIC HORMONE (ADH); FOLLICLE-STIMULATING
HORMONE (FSH); HYPERPROLACTINEMIA; LUTEINIZING
HORMONE (LH); OXYTOCIN.