Objective: To review the current literature regarding the prevalence of macroprolactin (macroPRL) in hyperprolactinemic patients and determine recommendations for testing.
Methods: An electronic United States National Library of Medicine PubMed search (through October, 2014) was conducted for search term "macroprolactin." Only English-language articles were considered.
Results: MacroPRL is an under-recognized cause of elevated prolactin (PRL) and is present in approximately 4% to 40% of hyperprolactinemic patients depending on the referral population. Clinical findings which could be due to hyperprolactinemia are the impetus for testing for PRL. Because of this there is significant overlap in the clinical presentation of patients with true hyperprolactinemia and those with macroPRL, differentiation cannot always be made on the basis of symptoms. A lack of recognition of the presence of macroPRL can lead to unnecessary laboratory investigations, imaging, and pharmacologic or surgical treatment.
Conclusion: Until there is a commercially available PRL assay that is not subject to interference by macroPRL, clinicians should consider the possibility of macroPRL, especially if the clinical presentation, imaging findings, and/or response to therapy reveal inconsistencies.