Remarkable Cystic Expansion of Microprolactinoma Causing Diabetes Insipidus during Pregnancy

Abstract

A 26-yr-old woman with galactorrhea had an elevated serum prolactin (PRL) level (75 ng/ml). Magnetic resonance imaging (MRI) revealed a 4-mm intrasellar tumor, suggesting a PRL-producing microadenoma. Cabergoline was prescribed and ameliorated the patient’s galactorrhea. No tumor growth was observed for 1 yr after MRI (Fig. 1), and cabergoline administration was discontinued when the patient became pregnant. At 24 wk gestation, she was admitted to the obstetrics department for intrauterine growth retardation. She developed polyuria (7700 ml/d) at 29 wk gestation and had a low serum arginine vasopressin (AVP) level (0.5 pg/ml). MRI revealed a 2-cm cystic lesion with suprasellar extension (Fig. 2). Her serum PRL level robustly increased (461 ng/ml), but visual field testing results were normal. Diabetes insipidus caused by cystic expansion of a prolactinoma was consid-