Macroprolactinaemia in a 33-year old premenopausal Nigerian woman: a case report

Abstract

Background: Macroprolactin is a 150-170kDa heteropolymeric complex of monomeric prolactin and immunoglobulin G (IgG) that contributes less than 1% of circulating prolactin concentration in plasma. It exerts little or no biological action in vivo. Its elevated plasma concentration (macroprolactinaemia) is a notable cause of frequent misdiagnosis, unnecessary investigation, and inappropriate treatment in patients with biochemical hyperprolactinaemia.

Objective: To highlight the need for macroprolactin screening in premenopausal women with biochemical hyperprolactinaemia.

Method: We report an investigated case of macroprolactinaemia in a 33-year old premenopausal nulliparons woman with sustained hyperprolactinaemia, normoovulatory and regular menstrual cycles, and no radiological evidence of pituitary tumour (prolactinoma).

Result: The patient had persistent hyperprolactinaemia even after treatment with bromocriptine for 1 month. The menstrual cycle remained regular with clinical and biochemical presumptive evidence of ovulation.

Conclusion: Macroprolactinaemia is a potential cause of (pseudo) hyperprolactinaemia in women of childbearing age. Its occurrence should be suspected and investigated especially in patients with hyperprolactinaemia and regular normoovulatory cycles. The polyethyleneglycol (PEG) precipitation test is a simple and cost-effective screening test for macroprolactinaemia.

Keywords: Prolactin, hyperprolactinaemia, macroprolactin, macroprolactinaemia