A case of squamous cell carcinoma of the tongue was complicated by post operative hyponatraemia. The criteria for the syndrome of inappropriate secretion of anti diuretic hormone, [ADH] (SIADH) were met but the patient remained hyponatraemic despite adequate treatment. The patient had previously received radical external radiotherapy to the neck and was found to be profoundly hypothyroid. Correction of the hypothyroid state led to clinical and biochemical recovery. The frequency of post-irradiation hypothyroidism and the possible mechanisms of hypothyroid-induced hyponatraemia are discussed

A case of tuberculous Addison's disease presenting with psychosis, profound hyponatraemia, and detectable plasma antidiuretic hormone is reported. Clinical and biochemical improvement after corticosteroid replacement was followed by relapse with further psychosis and inappropriate antidiuretic hormone secretion: both were promptly reversed by demethylchlortetracycline. The association of psychological symptoms with Addison's disease, the role of anti-diuretic hormone secretion in Addison's disease, and the inter-relationship between Addison's disease, psychosis and anti-diuretic hormone secretion are discussed.