INTRODUCTION: Recent studies show an association between hyponatremia and osteoporosis. We have previously reported a case of severe male osteoporosis due to chronic syndrome of inappropriate secretion of antidiuretic hormone (SIADH). Here, we provide a follow-up on this case after cure of the condition that further supports the causal relationship.

THE CASE: A 38-year-old man had been diagnosed with severe osteoporosis most likely due to chronic SIADH. The SIADH was believed to be idiopathic. A magnetic resonance imaging scan, however, revealed a tumor in the sinus, and biopsies showed an esthesioneuroblastoma, immunohistochemically positive for antidiuretic hormone (ADH). After the tumor was removed, ADH and sodium levels normalized. A dual-energy x-ray absorptiometry scan performed 7 months after the patient's last surgery showed a significant spontaneous improvement in bone mineral density in the lumbar vertebrae.

CONCLUSION: This case provides evidence for a causal relationship between SIADH and chronic hyponatremia and impaired bone metabolism that can lead to severe secondary osteoporosis. The effect on bone metabolism is at least partially reversible.