An unusual case of Cushing's syndrome due to bihormonal ACTH–prolactin secreting pituitary macroadenoma with rapid response to cabergoline

• Published in: BMJ case reports 2017-08, Vol.2017, p.bcr-2017-219921
• Main Authors: Kunasegaran, Shalini, Croxson, Michael S, Holdaway, Ian, Murphy, Rinki
• Format: Article
• Language: English
• Subjects: ACTH-Secreting Pituitary Adenoma - complications; ACTH-Secreting Pituitary Adenoma - drug therapy; Adenoma - complications; Adenoma - drug therapy; Adrenal glands; Antineoplastic Agents - therapeutic use; Australasia; Blood pressure; Cabergoline; Case reports; Cushing syndrome; Cushing Syndrome - etiology; Dopamine; Ergolines - therapeutic use; Hormones; Humans; Indian Sub-Continent; Laboratories; Male; Pituitary Neoplasms - complications; Pituitary Neoplasms - drug therapy; Prolactinoma - complications; Prolactinoma - drug therapy; Rare Disease; Surgery; Testosterone; Tumors; Young Adult
• ISSN: 1757-790X; 1757-790X
• DOI: 10.1136/bcr-2017-219921

A 23-year-old man presenting with florid Cushing's syndrome was found to have high plasma ACTH and very high serum prolactin. Pituitary MRI showed a large invasive macroadenoma. Low-dose cabergoline promptly suppressed both ACTH and prolactin levels within 2 weeks, with unexpected clinical and biochemical hypocortisolism requiring hydrocortisone replacement. Secondary hypogonadism was reversed. Clinical and biochemical remission of his Cushing's syndrome together with significant shrinkage of his macroadenoma has been maintained for 1 year on cabergoline 0.5 mg twice weekly. Reduction in pituitary tumour volume and brisk fall in serum prolactin in response to low-dose cabergoline is regularly observed in patients with macroprolactinomas, but the concurrent fall in the plasma ACTH level and hypocortisolism was a pleasant surprise. We assume that he most likely has a single bihormonal adenoma that is enriched with dopamine-2 receptors.