[A case of unilateral primary adrenal nodular hyperplasia with elevated plasma adrenocorticotropin (ACTH)]

A 57-year-old woman was admitted to our hospital with occipital headache and nausea. She had severe hypertension (192/122mmHg), hypokalemia (2.8mEq/l) and fasting hyperglycemia (127 mg/dl). Further examination revealed elevated plasma ACTH (124pg/ml) and cortisol (26.5 mu g/dl) with a lack of diurnal rhythm. Plasma ACTH or cortisol did not increase by injection of corticotropin releasing hormone (CRH). Rapid ACTH test resulted in an exaggerated response of plasma cortisol. Abdominal MRI scan showed a left adrenal tumor. Since the bilateral adrenal venous blood sampling revealed a significant increase of cortisol on the left, left adrenalectomy was performed. Histological examination of the resected adrenal gland revealed marked cortical hyperplasia. Postoperative investigations revealed that despite a small dose of steroid replacement for only 20 days, plasma ACTH level was decreased for a period of 6 months. Both plasma ACTH and cortisol increased by a CRH injection 38 days after surgery. CRH test during bilateral inferior petrosal sinus sampling indicated that this patient had no functioning pituitary tumor. Although the exact mechanism of high plasma ACTH level in this case was unknown, these findings suggest that any substance secreted from primary adrenal nodular hyperplasia adrenal nodular hyperplasia may stimulate pituitary ACTH production. This is a very rare case of Cushing's syndrome due to unilateral primary adrenal nodular hyperplasia with elevated plasma ACTH.