Frequency of macroprolactinemia in hyperprolactinemic patients with simple polyethylene glycol precipitation test

Hyperprolactinemia is seen not only in pregnancy but also in several pathological conditions, However, some patients with hyperprolactinemia are diagnosed as idiopathic, because the causes are unknown. They are subjected to repeated radiological examinations to find a microadenoma, to a long term treatment with bromocriptine, and even to a surgical intervention. There is evidence that macroprolactinemia, in which most circulating PRL form large protein complexes (>150 KDa), is a major cause of idiopathic hyperprolactinemia. Macroprolactinemic patients are clinically characterized by lack of or less hyperprolactinemia – related symptoms. The objective of this study was to assess the prevalence of macroprolactinemia in hyperprolactinemic patients. Prolactin was measured before and after precipitation of macroprolactin by polyethylene glycole in 113 hyperprolactinemic (PRL>28 µg/L patients. In 23% of the patients, macroprolactinemia was found. Considering the high prevalence of macroprolactinemia and to avoid diagnostic and therapeutic pitfalls, the screening for macroprolactinemia in all hyperprolactinemic patients is recommended.