Steroid therapy in inappropriate secretion of antidiuretic hormone due to malignant thymoma

The authors present the case of a 48-year-old female known to have malignant thymoma with metastases for 6 years and treated continuously for 4 years by corticosteroids with marked regression of tumor. The patient ceased medication on her own accord, and was admitted with extensively enlarged tumor and metastases in association with the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). In view of the previous excellent response of the thymoma to corticosteroids, the same treatment was given again with disappearance of the tumor and the features of SIADH. The authors are unaware of previous use of corticosteroids in SIADH as a consequence of their effect on tumor regressions.