Ectopic ACTH secretion accounts for 1125% of Cushings syndrome, most commonly resulting from small cell lung carcinoma and bronchial carcinoid tumours. Ectopic ACTH requires meticulous consideration in the differential of ACTH-dependent Cushings syndrome. Thymic carcinoids are a very rare cause of ectopic ACTH secretion, accounting for 512% of cases. A 28 year old gentleman was diagnosed with Cushings syndrome after presenting with lethargy, hypertension, facial and central adiposity, plethoric facies, central obesity, violaceous abdominal striae, ankle oedema, proximal myopathy and acute onset back pain. Spinal XRs showed low bone mass and wedge fractures of T8, T9, and T10. Whilst undergoing investigation of Cushings syndrome he presented with acute dyspnoea. A CTPA confirmed bilateral pulmonary emboli and was incidentally noted to have an anterior mediastinal mass 3×2×4.5 cm distal to the thyroid, suggestive of a thymoma. Pituitary MRI revealed a 4 mm adenoma. Adrenal MRI, pituitary function, and calcium were normal. 24 hour urine free cortisol >4320 nmol/day Overnight DST (1 mg): Cortisol 606 nmol/l 9 am ACTH : 119 ng/l (050) He was commenced on metyrapone, alendronate, calcium/vitamin D and low molecular weight heparin. Guided by cortisol day curves, metyrapone was uptitrated to 500 mg qds with addition of hydrocortisone in a block and replacement regimen. CT guided biopsy of the thymic mass showed a well differentiated neuroendocrine carcinoma. Octreotide scan revealed low grade uptake by the tumour and no evidence of distance metastasis. He underwent sternotomy with resection of the thymic tumour. Day 3 post-operatively cortisol level was 370 nmol/l, with a day curve range of 270356 nmol/l, suggesting significant improvement, but not cure of his hypercortisolism. His Cushingoid features improved substantially over the next weeks. The metyrapone was not recommenced post-operatively though he was commenced on prn hydrocortisone for intercurrent illness. IPSS and genetic testing for MEN1 remain outstanding.
Declaration of interest: There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.
Funding: No specific grant from any funding agency in the public, commercial or not-for-profit sector.