Prolactin

Prolactin is a protein that in humans is encoded by the PRL gene. Prolactin, which is a peptide hormone, may also be called luteotropic hormone (LTH). It is most known for its role in lactation, but it has more than 300 known effects, including stimulating proliferation of oligodendrocyte precursor cells, contributing to surfactant synthesis of the fetal lungs at the end of pregnancy and some effects dealing with sexual arousal and gratification. Prolactin also existed in the oldest known vertebrates — fish — most likely to control the balance between water and salt.

How it works

Prolactin helps to regulate the immune system by acting in a cytokine manner. It helps the cell cycle in functions, including growth, differentiating and anti-apoptotic factor.

The hormone is regulated by endocrine neurons in the hypothalamus.

When patients require a sex hormone workup, prolactin levels may be checked. Elevated secretion of prolactin can suppress the secretion of follicle-stimulating hormone and gonadotropin-releasing hormone, which could, in turn, lead to hypogonadism. It may also cause sexual dysfunction in men. Experts have also used prolactin levels to determine whether a seizure was epileptic or psychogenic non-epileptic. Epileptic seizures may be marked by an increase in serum prolactin level.

Pregnant women demonstrate high circulating levels of estrogen and progesterone, which inhibits the mechanism of prolactin that produces milk. When estrogen and progesterone are reduced after childbirth, milk is produced. Fathers or expectant fathers also may have higher prolactin concentrations than other men.

Individuals are more likely to demonstrate hypersecretion of prolactin than hyposecretion.

Prolactin levels

The following levels are considered normal:

men: 2-18 ng/mL;
non-pregnant women: 2-29 ng/mL; and
pregnant women: 10-209 ng/mL.

Abnormal prolactin levels could indicate a variety of conditions, including chest wall trauma or irritation, hypothalamic disease, hypothyroidism, kidney disease and a pituitary tumor that produces prolactin.

Medications could also raise prolactin levels, including antidepressants, estrogens and H2 blockers, among others.

Additional information may be found at these websites:

http://bloodjournal.hematologylibrary.org/cgi/collection/gene_expression

http://www.nlm.nih.gov/medlineplus/ency/article/003706.htm

http://www.mayoclinic.com/health/metabolism/WT00006/

http://www.nature.com/jcbfm/index.html

http://www.nutritionandmetabolism.com/

http://www.hormone.org/Public/endocrinologist.cfm

http://www.nlm.nih.gov/medlineplus/ency/article/002257.htm

http://www.ncbi.nlm.nih.gov/books/NBK22/?depth=10

http://endo.endojournals.org/

http://www.mayoclinic.org/medicalprofs/glucocorticoid-induced-diabetes.html