Soluble Fas is increased in hyperthyroidism independent of the underlying thyroid disease

In Hashimoto's thyroiditis, Fas-induced apoptosis is one of the mechanisms leading to cell destruction, whereas thyroid tis. sue in Graves' disease is prevented from it. The soluble form of the Fas molecule produced by altern ative splicing prevents from apoptosis. We measured soluble Fas in the sera of 112 patients with Graves' disease, 21 patients with toxic goiter, and 2 4 patients with subclinical hyperthyroidism due to suppressive therapy with levothyroxine after near-total resection of the thyroid gland for nodular goiter. Soluble Fas was increased in thyrotoxic patients, toxic goiter, and patient s with subclinical hyperthyroidism. Decreased levels of soluble Fas were fo und in euthyroid patients with Graves' disease after surgery, whereas solub le Fas was normal in euthyroid patients with Graves' disease receiving anti thyroid drug treatment and in patients in stable remission. There was a goo d correlation between soluble Fas with free T-s (r=0.6) and free T-4 (r=0.5 ). Our results show that soluble Fas is increased in hyperthyroidism indepe ndent of the underlying thyroid disease.