Macroprolactinemia: clinical significance and characterization of the condition

Area of Science:

• Endocrinology
• Immunology
• Reproductive Medicine

Background:

• Hyperprolactinemia is a common endocrine disorder.
• Macroprolactinemia (bb PRL) is a variant of hyperprolactinemia, often associated with prolactin-IgG complexes.
• The clinical significance and bioactivity of macroprolactinemia remain incompletely understood.

Purpose of the Study:

• To characterize the clinical presentation of patients with macroprolactinemia.
• To investigate the potential association between macroprolactinemia and autoimmune syndromes.
• To evaluate the in vitro and in vivo bioactivity of macroprolactin.

Main Methods:

• PEG precipitation test to identify macroprolactinemia in hyperprolactinemic patients.
• Hormonal and autoimmune screening, including IV TRH test.
• Nb2 assay for serum prolactin bioactivity and immunoprecipitation with anti-IgG antibodies to determine biochemical nature.

Main Results:

• 14 out of 82 hyperprolactinemic patients had macroprolactinemia (bb PRL).
• 79% of patients presented with symptoms like infertility or galactorrhea, often attributable to other conditions.
• bb-PRL showed in vitro bioactivity, but variable in vivo bioactivity, likely due to reduced vascular endothelium permeability. 85% of bb-PRL samples were PRL-IgG complexes.
• No clinical or laboratory evidence of autoimmunity was found.

Conclusions:

• Macroprolactinemia is characterized by PRL-IgG complexes with variable in vivo bioactivity.
• Symptoms in macroprolactinemic patients are often unrelated to hyperprolactinemia itself.
• Macroprolactinemia does not appear to be part of an autoimmune syndrome.