Case Report

Macroprolactinemia in a Patient with Infertility and Hyperprolactinemia

Authors: Hasnain M. Khandwala, MD, FRCPC

Abstract

A significant number of patients with hyperprolactinemia have macroprolactinemia, a condition characterized by the preponderance of big-big prolactin with normal levels of free prolactin. As macroprolactin does not have biologic activity, such patients do not require further investigations or treatment for hyperprolactinemia. The case of a patient with hyperprolactinemia diagnosed during investigation of secondary infertility is presented. She was treated for over 2 years with dopamine agonists, with which her prolactin level normalized, but she remained infertile. Subsequent investigations demonstrated that she suffered from macroprolactinemia, not true hyperprolactinemia. The patient is currently not on dopamine agonist therapy, and although her total prolactin levels remain significantly elevated, her free prolactin levels have been in the normal range. Physicians should familiarize themselves with this entity and consider testing for it in patients with hyperprolactinemia to avoid an inappropriate diagnosis and unnecessary treatment.


Key Points


* Macroprolactinemia is a condition characterized by elevated total prolactin levels due to a preponderance of big-big prolactin with normal levels of free prolactin.


* Macroprolactinemia may be present in up to 45% of patients with hyperprolactinemia.


* Macroprolactin does not have biologic activity and patients with macroprolactinemia do not require pituitary imaging or treatment with dopamine agonists.


* Physicians should familiarize themselves with this entity and consider further testing for macroprolactinemia in patients with hyperprolactinemia.

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