Uterine Fibroid Causing Hyperprolactinemia and Paradoxical Prolactin Rise with Dopamine Agonist: Case Report and Systematic Review

Hyperprolactinemia in premenopausal women often presents with amenorrhea, symptoms of estrogen deficiency and sub-fertility. After exclusion of other common causes and in the context of a normal pituitary MRI scan, hyperprolactinemia is typically deemed “idiopathic.” Here we present a case where excess prolactin secretion was attributed to a uterine fibroid and following myomectomy the hyperprolactinemia and its clinical sequelae resolved. Following 6 years of secondary infertility, a 41-year-old woman presented with secondary amenorrhea, expressible galactorrhea, and symptoms of estrogen deficiency. Prolactin levels were consistently raised (1300 mU/L to 2100 mU/L, reference interval < 600 mU/L), and repeated pituitary imaging demonstrated no pituitary abnormality. Prolactin levels demonstrated a paradoxical rise in response to dopamine agonist therapy (2000 mU/L to 5900 mU/L). Imaging demonstrated a uterine fibroid and the patient underwent myomectomy. Following myomectomy, prolactin levels became undetectable, galactorrhea and symptoms of estrogen deficiency resolved, menses returned, and a planned unassisted pregnancy followed. Ectopic prolactin secretion from uterine fibroids is a rare cause of hyperprolactinemia and can result in the same clinical sequelae as pituitary causes. As ectopic prolactin secretion is not under inhibitory control of dopamine, it is usually resistant to, or may rise in response to, dopamine agonist therapy. Prior to a diagnosis of “idiopathic” hyperprolactinemia, ectopic sources of prolactin should be considered.