Clinical Significance of Elevated Macroprolactin Levels in Patients with Hyperprolactinemia. Case report

Abstract

Introduction: Hyperprolactinemia is the most common abnormality of the hypothalamic-pituitary axis and is the most frequent manifestation of functional pituitary adenomas. Macroprolactin is a non-bioactive prolactin isoform usually composed of a prolactin monomer and an IgG molecule. Despite being clinically non-reactive, it interferes with immunological assays used for the detection of prolactin. Macroprolactin is a significant cause of misdiagnosis, unnecessary investigation, and inappropriate treatment in patients with hyperprolactinemia. Despite its estimated prevalence in up to 46% in patients with hyperprolactinemia, macroprolactin is one of the less commonly considered etiologic factors. Materials and Methods: An overview of scientific publications on the database of the National Library of Medicine and PubMed Central and a case report are presented. Results: We present a case report of a 22-year-old female patient, who was admitted at the Endocrinology Department of the St. Marina University Hospital, Varna. The patient complains of irregular menstrual cycle, persisting headache for six months, which is lightly influenced by analgesics, and presents outpatient laboratory results of prolactin (1206 mIU/ml) and normal LH, FSH and E2 levels. The MRI scan of the head shows no pathological findings in the pituitary gland. The levels of the macroprolactin are measured using the polyethylene glycol (PEG) precipitation method and show a total of 952 mIU/ml, and prolactin of only 518 mIU/ml. Conclusion: Macroprolactin is commonly found in patients with hyperprolactinemia; however, neither symptoms nor MRI findings are useful in predicting its presence. Patients with macroprolactinemia commonly have symptoms similar to those with elevation in monomeric prolactin only, but its clinical significance remains uncertain. The presence of macroprolactin should always be suspected in patients with hyperprolactinemia.