Clinical Significance

Prolactin is synthesized in the anterior pituitary and is secreted in episodes. The hormone is made up of 198 amino acids and has a molecular weight of approximately 22‑23 kDa. Prolactin appears in serum in three different forms. The biologically and immunologically active monomeric form predominates (approximately 80 %), 5‑20 % is present as the biologically inactive dimeric form and 0.5‑5 % is present as the tetrameric form having low biological activity. The target organ for prolactin is the mammary gland, the development and differentiation of which is promoted by this hormone. High concentrations of prolactin have an inhibiting action on steroidogenesis of the ovaries and on hypophyseal gonadotropin production and secretion. 

During pregnancy the concentration of prolactin rises under the influence of elevated estrogen and progesterone production. The stimulating action of prolactin on the mammary gland leads post partum to lactation. 

Hyperprolactinemia (in men and women) is the main cause of fertility disorders. The determination of prolactin is utilized in the diagnosis of anovular cycles, hyperprolactinemic amenorrhea and galactorrhea, gynecomastia and azoo-spermia. Prolactin is also determined when breast cancer and pituitary tumors are suspected.

_{Source: Roche cobas Elecsys Prolactin II method sheet, V 3.0 2024-10}