Serum prolactin binding in various forms of hyperprolactinemia

Binding of 125I-labeled prolactin in the sera of women with different forms of hyperprolactinemia was studied. Antiprolactin autoantibodies were detected in the blood of 24% of women with idiopathic hyperprolactinemia. In contrast to idiopathic hyperprolactinemia, there were no autoantibodies to prolactin in pregnant women with physiological hyperprolactinemia and in hyperprolactinemia of tumor origin. These data indicate that the presence of these antibodies in circulating blood can be one cause of idiopathic hyperprolactinemia. Moreover, the prevalence of high-molecular form of immunoreactive prolactin in the blood can be due to binding of an appreciable amount of prolactin monomer to antiprolactin autoantibodies.