Hyponatremia in pulmonary TB: evidence of ectopic antidiuretic hormone production.

Hyponatremia is among the most common biochemical abnormalities in hospital inpatients. The syndrome of inappropriate antidiuretic hormone secretion (SIADH) is one of several causes of hyponatremia, particularly in patients with pulmonary diseases. The mechanism of SIADH associated with pulmonary infection is, however, poorly understood. We report an unusual case of hyponatremia in a man with pulmonary TB and central diabetes insipidus with biochemical evidence of ectopic antidiuretic hormone production as a possible mechanism causing hyponatremia.