Macroprolactin

This test is recommended as an adjunct to the Prolactin assay when elevated Prolactin levels (>33 ng/ml) are detected, which will greatly increase the diagnostic value of the test results.

Prolactin ("promotion", "lactation" in English) is a hormone produced by the pituitary gland. The main functions of prolactin in women are to stimulate the growth of the mammary glands and the production of milk during pregnancy and lactation. In men, the hormone provides testosterone production and regulates sperm activity. Increased prolactin levels (hyperprolactinemia) are pathological (with the exception of pregnancy and breastfeeding) and are most often seen in the case of a benign prolactin-producing pituitary tumour - prolactinoma. Rarely, the tumour is asymptomatic. In other cases it may cause menstrual disorders or even full cessation of the menstrual cycle, mammary gland discharge, absence of ovulation and infertility in women.

In men too high prolactin levels lead to lower blood levels of testosterone and impaired spermatogenesis (spermatozoa formation). This leads to decreased libido, potency and infertility.

There are three forms of prolactin in the blood:

85 % - in the form of monomer (monoprolactin), this is the most active form of prolactin;
10% as a dimer (bigprolactin);
5% is a complex of prolactin monomer and immunoglobulin G, called macroprolactin (big-bigprolactin); this form is the largest (its molecular weight is about 200 kD) but is the least active.

Macroprolactin is eliminated from the blood in a much longer period of time than forms of prolactin with a smaller molecular weight. For this reason, macroprolactin has the ability to accumulate in the blood in high concentrations. This form is the least biologically active, unlike other forms of prolactin circulating in the blood, so high prolactin hyperprolactinemia (macroprolactinemia) has no or little symptoms and most often manifests as menstrual irregularities. Other more severe symptoms (galactorrhoea, infertility) are rare.

Hypermacroprolactinemia (as opposed to hyperprolactinemia) is not a risk for diseases such as osteoporosis and breast cancer.