Remission of acanthosis nigricans, hypertrichosis, and Hashimoto's thyroiditis with thyroxine replacement.

Hypothyroidism is not commonly associated with acanthosis nigricans (AN). We examined a 13-year-old girl with AN, hypertrichosis, and Hashimoto's thyroiditis. Overt biochemical hypothyroidism, thyroid enlargement, and positive titers of antimicrosomal and antithyroglobulin antibodies confirmed Hashimoto's thyroiditis. Both AN and hypertrichosis resolved with thyroid hormone replacement. There was no evidence of insulin resistance, polycystic ovarian disease, lipoatrophy, or other endocrine dysfunction, or of malignancy. In two patients from the literature with AN and hypothyroidism, AN was attributed to associated thyroid carcinoma or insulin resistance, rather than coexisting hypothyroidism. Since the skin lesions improved with thyroid hormone therapy in those two patients and in ours, hypothyroidism appears to be directly involved in the pathogenesis of AN.