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Statin drugs may increase thyroid secretion and decrease autoimmunity in patients with Hashimoto’s thyroiditis

The background of the study. Hashimoto’s thyroiditis is characterized by the intrathyroidal accumulation of lymphocytes and injury to thyroid cells, and therefore hypothyroidism. Statin drugs inhibit the synthesis of cholesterol and its precursors, and may also have immunomodulatory actions. This study evaluated the effects of a statin on thyroid function and circulating lymphocytes in patients with Hashimoto’s thyroiditis.

How the study was done. The studies were done in 21 patients with subclinical hypothyroidism caused by Hashimoto’s thyroiditis. All the patients had thyroid enlargement, high serum thyrotropin (TSH) concentrations, normal serum free thyroxine (T4) concentrations, high serum antithyroid antibody concentrations, and lymphocytic infiltration of the thyroid. They were randomly assigned to receive simvastatin, 20 mg daily, or no treatment for 8 weeks. Serum TSH, free T4, and antithyroid antibodies were measured at base line and 8 weeks. The percentages of different types of lymphocytes in peripheral blood also were measured at these times.

The results of the studies. The serum free T4 concentrations increased and serum TSH concentrations decreased in the patients treated with simvastatin (Table), but there was no change in serum antithyroid antibody concentrations. There was an increase in lymphocytes with immune suppressor activity and a decrease in cells with killer activity. There were no changes in the 10 untreated patients.

The conclusions of the study. A statin drug improves thyroid function in patients with subclinical hypothyroidism caused by Hashimoto’s thyroiditis.

The original article. Gullu S, Emral R, Bastemir M, Parkes AB, Lazarus JH. In vivo and in vitro effects of statins on lymphocytes in patients with Hashimoto’s thyroiditis. Eur J Endocrinol 2005;153:41-8.