The macroprolactinemia phenomenon: origin and clinical diagnostic significance

The authors discuss the experimental and clinical data on the origin, properties, and diagnostic value of serum immunoreactive prolactin (irPRL) with a high molecular mass (macroprolactin, 100K-PRL). This form predominates in the blood of about 25% of women of a reproductive age with hyperprolactinemia. Comparison of the biochemical, immunochemical, and functional characteristics of the blood serum 100K-PRL and the monomeric fraction irPRL (23K-PRL) showed them to differ in principle. A low biological activity of 100K-PRL explains the absence of typical clinical signs of hyperprolactinemia in many women with macroprolactinemia. In contrast to 23K-PRL, 100K.-PRL weakly reacts to stimulants and inhibitors of PRL secretion by the pituitary. PRL-binding protein, apparently an immunoglobulin, is the basis of fraction 100K-PRL. The authors consider that analysis of not only total irPRL in the blood, but of its high and low-molecular forms be included in the algorithm of diagnostic search in some forms of hyperprolactinemia. This will help determine the treatment policy, because moderate hyperprolactinemia with predominating 100K- PRL as a rule cannot be corrected by dopamine agonists.