Macroprolactin

Macroprolactin is a high-molecular-weight form of prolactin, which is a complex of the hormone with immunoglobulins. Unlike biologically active monomeric prolactin, macroprolactin has virtually no physiological effect on body tissues.

In a standard prolactin test, the laboratory method does not distinguish between active and inactive fractions, which is why the total prolactin level may be elevated without clinical manifestations.

Clinical significance of the test

Detection of macroprolactin allows you to:

distinguish true hyperprolactinemia from a laboratory phenomenon;
avoid misdiagnosis of pituitary diseases;
prevent unnecessary MRI scans and drug therapy;
correctly interpret elevated prolactin in the absence of symptoms.

A condition in which the increase in prolactin is mainly due to macroprolactin is called macroprolactinemia. It usually does not require treatment.

Why is this important

The biological activity of macroprolactin is extremely low. Patients with macroprolactinemia most often:

do not have menstrual cycle disorders;
do not experience infertility;
do not complain of symptoms characteristic of hyperprolactinemia.

Without the isolation of the macrofraction, there is a risk of overdiagnosis and prolonged unnecessary treatment.

How the test is performed

The test is performed by precipitating macromolecular complexes, followed by the detection of residual (biologically active) prolactin.

The result allows us to assess which part of the total prolactin is truly significant.

Important notes

Macroprolactin testing is not a standalone screening test:

Macroprolactin testing is only performed after elevated prolactin has been detected.
With normal or low prolactin, macroprolactin may not be detected, which is a normal variant.
The decision on the need for examination is made by an endocrinologist or gynecologist.