Endocrine Abstracts

The syndrome of inappropriate secretion of antidiuretic hormone (SIADH) occurs in 10-45% of patients and secretion of ectopic adrenocorticotrophic hormone (EAS) in 2.5% of patients with small cell lung cancer (SCLC). Simultaneous secretion of ADH and ACTH is rare with only 10 cases being reported. The varying biochemical data leads to misdiagnosis as this case demonstrates. A 67 year old male presented with a 2 week history of falls attributed to alcohol abuse. Physical signs were unremarkable. Investigations: sodium 111 mmol/l, serum osmolality 235 mmol/kg and urine osmolality 467 mmol/kg suggested a diagnosis of SIADH. CXR was normal and cortisol 382 nmol/l. Fluid restriction and demeclocycline 150 mg bd improved sodium to 128 mmol/l. At review 2 months later sodium remained unchanged at 128 mmol/l and demeclocycline was increased to 300 mg bd. CT imaging 1 month later confirmed a subcarinal mass and metastases throughout the abdomen. Referral for biopsy was made but 2 weeks later he presented with generalised oedema and leg weakness. Proximal myopathy was confirmed. Investigations: sodium 143 mmol/l, potassium 2.5 mmol/l, pH 7.43, bicarbonate 28.6 mmol/l, cortisol 3104 nmol/l and ACTH 209.1 ng/l. A diagnosis of primary hyperaldosteronism was made and the cortisol level attributed to stress. Referral to endocrinology resulted in diagnostic revision. In view of his poor physical state and extensive metastatic disease oncology opined that symptomatic treatment was appropriate. Metyrapone and spironolactone improved clinical and biochemical status transiently (potassium 4.3 mmol/l, cortisol 731 nmol/l) and he died 2 months later. Cases of SCLC secreting both ADH and ACTH tend to have more extensive disease at presentation and poorer prognosis. Hypercortisolaemia has been invoked as the cause of the latter due to enhanced tumour growth, high rate of metastases, hyperglycaemia, hypokalaemia and infection.