Endocrine Abstracts

This is a case of a patient diagnosed with small cell lung carcinoma after presenting with severe hyponatremia due to syndrome of inappropriate antidiuretic hormone secretion (SIADH) who was readmitted 7 months later with refractory hypokalemia and hyperglycaemia due to ectopic adrenocorticotrophic hormone secretion (EAS). A 65 year-old man presented in November 2018 with symptoms of nausea, vomiting, headaches and blurred vision. On examination he was clinically euvolemic. Laboratory results revealed sodium of 117 mmol/l without other electrolyte abnormalities, serum osmolality 256 mOsm/kg, cortisol 322 nmol/l, urine sodium 112 mOsm/kg, urine osmolality 499 mOsm/kg and normal TFTs, results consistent with SIADH. He had no drug history and was an ex-smoker. Hyponatremia was managed with hypertonic saline and demeclocycline. CT Scan and PET-CT showed left hilar mass but no metastasis (stage T2aN0M0). Bronchosopic guided tissue biopsy + histology confirmed SCLC immunoreactive with CD 56, synaptophysin and chromogranin. In the following weeks he completed a full course of chemotherapy and radiotherapy. The patient was re-admitted in May 2019 with severe hyperglycaemia and refractory hypokalemia associated with hyperpigmentation, peripheral oedema and increased abdominal adiposity. Biochemistry showed baseline 0900 h cortisol of >1650 nmol/l without suppression following dexamethasone, urine cortisol >6905 nmol/24H and high ACTH levels, results compatible with ectopic ACTH secretion from the SCLC. Unfortunately our patient’s condition deteriorated rapidly soon after being diagnosed with Cushing’s syndrome due to EAS on top of SIADH and soon developed pancytopenia with acute liver failure and sadly passed away 14 days after diagnosis of ectopic ACTH secretion from SCLC. So far only 8 cases with SCLC with dual SIADH and EAS have been described in literature, the development of EAS being associated with the worst prognosis and shortest median survival.