A case of Cushing's syndrome in a pregnant woman associated with hypertension, hypokalemia, and gestational diabetes mellitus

We report the case of a 33-year-old woman who was referred to the department of endocrinology and diagnosed with gestational diabetes mellitus (GDM). She had been hypertensive from 20 weeks of pregnancy. A 75 g oral glucose tolerance test for screening of GDM at 26 weeks of pregnancy revealed positive results at two points: 183 mg/dL at 60 min, and 193 mg/dL at 90 min. At the first visit to the Department of Endocrinology, Cushing's features were clinically unclear. She started self-monitoring blood glucose levels, and hypokalemia was detected. At 28 weeks of pregnancy, she was admitted to our hospital because of uncontrolled blood pressure. The patient started multiple injections of rapid insulin for postprandial hyperglycemia. Laboratory testing revealed suppressed plasma ACTH (< 1.5 pg/mL) and elevated serum cortisol levels (34.1 μg/dL) in the early morning. Because of uncontrollable pregnancy related complications, the patient delivered a baby by Caesarean section at 29 weeks of pregnancy. After delivery, she was diagnosed with ACTH-independent Cushing's syndrome by endocrinological tests. Computed tomography scan demonstrated a right adrenal tumor measuring 24 mm at greatest dimension. Twenty-three days after delivery, laparoscopic right adrenalectomy was performed. The diagnosis of cortisol-producing adrenocortical adenoma was pathologically confirmed. After surgery, the patient was given glucocorticoids as a replacement, and her blood pressure, blood glucose, and serum potassium levels were normalized. Although rare, GDM may be caused by Cushing's syndrome. Pregnant women with combinations of GDM, hypertension, and hypokalemia should be clinically suspected as harboring Cushing's syndrome even in the absence of specific clinical features.