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Hyperprolactinemia, characterized by abnormally high levels of prolactin, may cause galactorrhea (production and spontaneous flow of breast milk), infertility, and menstrual disruptions in women. In men, it can lead to hypogonadism, infertility and erectile dysfunction. Prolactin is crucial for milk production during pregnancy and lactation.
Prolactin levels peak during REM sleep and in the early morning. Many mammals experience a seasonal cycle. [38] During pregnancy, high circulating concentrations of estrogen and progesterone increase prolactin levels by 10- to 20-fold. Estrogen and progesterone inhibit the stimulatory effects of prolactin on milk production.
Galactorrhea hyperprolactinemia is increased blood prolactin levels associated with galactorrhea (abnormal milk secretion). It may be caused by such things as certain medications, pituitary disorders and thyroid disorders. The condition can occur in males as well as females.
During pregnancy, the production of prolactin by the mother increases steadily, starting at 6–8 weeks of gestation and continuing until the end of the pregnancy. [32] Prolactin levels in the human fetal circulation see a gradual increase from around 30 weeks of gestation until birth. [ 32 ]
Estrogen and progesterone cause the secretion of high levels of prolactin from the anterior pituitary, [32] [33] which reach levels as high as 20 times greater than normal menstrual cycle levels. [31] IGF-1 and IGF-2 levels also increase dramatically during pregnancy, due to secretion of placental growth hormone (PGH). [34]
High levels of prolactin during pregnancy and breastfeeding also increase insulin resistance, increase growth factor levels (IGF-1) and modify lipid metabolism in preparation for breastfeeding. During lactation, prolactin is the main factor maintaining tight junctions of the ductal epithelium and regulating milk production through osmotic balance.
A prolactin cell (also known as a lactotropic cell, epsilon acidophil, lactotrope, lactotroph, mammatroph, mammotroph) is a cell in the anterior pituitary which produces prolactin (a peptide hormone) in response to hormonal signals including dopamine (which is inhibitory), thyrotropin-releasing hormone and estrogen (especially during pregnancy), which are stimulatory.
A prolactinoma is a tumor of the pituitary gland that produces the hormone prolactin.It is the most common type of functioning pituitary tumor. [1] Symptoms of prolactinoma are due to abnormally high levels of prolactin in the blood (hyperprolactinemia), or due to pressure of the tumor on surrounding brain tissue and/or the optic nerves.