Addison's disease and corticosteroid-reversible hypothyroidism.

We report the case of a 28-year-old man who presented with idiopathic adrenal insufficiency and subclinical hypothyroidism documented by elevated basal thyrotropin level with abnormal response to thyrotropin-releasing hormone administration. Anti-thyroid antibodies were present in high titer, supporting the diagnosis of Hashimoto's thyroiditis, and hence of autoimmune polyglandular syndrome type II. The patient was not submitted to thyroxine therapy, and during cortisol replacement thyroid function improved, as judged by normalization of basal and stimulated thyrotropin and elevation of thyroid hormone levels. Anti-thyroid antibodies titer significantly diminished, and a short-time withdrawal of corticosteroids was not followed by elevation of thyrotropin hormone levels. Possible pathogenetic mechanisms of cortisone-induced remission of hypothyroidism due to chronic lymphocytic thyroiditis are discussed.