Relationship of antibodies to thyrotropin receptors and to thyroid ultrasonographic volume in euthyroid and hypothyroid patients with autoimmune thyroiditis.

It has been reported in hypothyroid patients with Hashimoto's thyroiditis and in patients with primary myxoedema that antibodies (Ab) to the TSH-receptor (R), which inhibit the thyroid gland, decrease both thyroid hormonogenesis and cell growth in vitro. We investigated, in 169 newly diagnosed patients with euthyroid (n = 83) or hypothyroid (n = 86) autoimmune thyroiditis, the relationship between thyroid autoimmunity expression and thyroid ultrasonographic volume or thyroid hormonal status. In patients positive for TSH-receptor (R) antibodies (Ab), negative correlations (P < 0.01) were found between TSH-R Ab levels and free T4 (FT4) values in a euthyroid (r = -0.63), as well as in a hypothyroid (r = -0.54) state, and between TSH-R Ab and total thyroid volume (TTV) values in an euthyroid (r = -0.62) as well as in a hypothyroid (r = -0.53) state. In contrast, no positive correlations were found between TSH levels and FT4 values or TTV levels in patients positive as well as negative for TSH-R Ab in an euthyroid or in a hypothyroid state. These data demonstrate in vivo, that, in contrast to TSH, TSH-R Abs are related to both thyroid hormonal production and volume in euthyroid or hypothyroid patients with autoimmune thyroiditis.