Endocrine Abstracts

A 70-year-old woman was referred to the endocrine clinic with recently diagnosed diabetes mellitus and poorly controlled systemic hypertension. At presentation she had clinical features of Cushing’s syndrome including central obesity, Cushingoid facies and marked proximal myopathy. BP was 220/190. Initial biochemistry revealed plasma sodium 140 mmol/l, potassium 3.6 mmol/l and creatinine 82 mmol/l. Overnight 1 mg dexamethasone suppression test revealed cortisol 1148 mmol/l and 24-h urinary free cortisol was markedly elevated at 2334 mmol/24 h. ACTH was also elevated at 169 mg l (NR 0–50 mg/l).

A diagnosis of ACTH-dependent Cushing’s syndrome was made. The patient was further investigated by means of low-dose dexamethasone test (48-h cortisol 956 mmol/l). Pituitary MRI and whole body CT did not identify a tumour as source of excessive ACTH production. A corticotrophin-releasing hormone stimulating test with petrosal sinus sampling failed to identify a pituitary source of ACTH. We proceeded to an octrectide scan which revealed increased uptake in the right iliac fossa, however abdominal CT did not identify any tumour and she never developed gastrointestinal symptoms.

As a primary source of excess ACTH was not identifiable the patient was commenced on metyrapone 500 mg three times daily. This supressed urinary fee cortisol into the normal range (238 mmol/24 h). She had repeated octreotide scans at one and two years that remained unchanged however repeated CT scans did not show a source of ACTH.

For the subsequent 8 years she continued to stay well. The clinical symptoms of Cushing’s syndrome resolved on metyrapone and urinary free cortisol remained normal.

Ten years from diagnosis she discontinued metyrapone of her own accord. Repeated urinary free cortisol measurements off metyrapone were found to be normal and no clinical features of Cushing’s syndrome have returned.

There are no previous reports of spontaneously resolving ectopic ACTH-dependent Cushing’s syndrome and this should be considered in the evaluation of patients with ectopic ACTH-dependent Cushing’s.