macroprolactinemia

Macroprolactinemia is a condition in which most circulating prolactin is present as a high‑molecular‑weight complex, usually prolactin bound to immunoglobulin G (IgG), known as macroprolactin. This form has reduced biological activity compared with monomeric prolactin and often yields elevated prolactin levels on standard immunoassays despite little or no clinical symptoms.

Clinical features vary. Many individuals with macroprolactinemia are asymptomatic. When symptoms occur, they are typically mild or attributable to true hyperprolactinemia from another cause, such as pituitary disease or medication effects. Distinguishing macroprolactinemia from genuine hyperprolactinemia is important because management differs.

Diagnosis relies on distinguishing macroprolactin from monomeric prolactin. The most common approach is a polyethylene glycol (PEG) precipitation test or gel filtration chromatography to determine the proportion of biologically active monomeric prolactin. If the majority of measurable prolactin is macroprolactin and free monomeric prolactin is normal, the condition is diagnosed as macroprolactinemia. Clinicians also review clinical symptoms and may perform pituitary imaging if indicated by the overall clinical picture.

Management generally involves observation and patient education. If macroprolactinemia is identified in an asymptomatic patient, no specific treatment is required and unnecessary pituitary imaging or dopamine‑agonist therapy is usually avoided. If true hyperprolactinemia or symptoms are present, appropriate evaluation and treatment for those underlying conditions should be pursued. Prognosis is typically favorable in isolated macroprolactinemia.