Macroprolactinemia: diagnostic, clinical, and pathogenic significance

Area of Science:

• Endocrinology
• Immunology
• Clinical Chemistry

Background:

• Macroprolactinemia involves large prolactin (PRL) complexes, often with IgG and anti-PRL autoantibodies.
• It presents as hyperprolactinemia without typical symptoms and affects 10-25% of hyperprolactinemia patients.

Purpose of the Study:

• To define macroprolactinemia, its characteristics, prevalence, and diagnostic approaches.
• To differentiate macroprolactinemia from other causes of hyperprolactinemia, avoiding unnecessary interventions.

Main Methods:

• Polyethylene-glycol (PEG) precipitation for screening.
• Gel filtration chromatography, protein A/G column, and I125-PRL binding studies for confirmation.
• Analysis of autoantibody epitope and PRL receptor binding site interaction.

Main Results:

• Macroprolactin, a PRL-IgG complex, is the primary form in sera, leading to elevated total PRL levels.
• Macroprolactin exhibits lower biological activity due to autoantibody binding near the PRL receptor site.
• Delayed clearance of autoantibody-bound PRL causes hyperprolactinemia.

Conclusions:

• Macroprolactinemia is a prevalent, chronic condition often developing before middle age.
• Screening for macroprolactinemia is essential for accurate hyperprolactinemia diagnosis.
• Distinguishing macroprolactinemia avoids unnecessary patient examinations and treatments.