Studies of Serum Triiodothyronine, Thyroxine and Thyrotropin Concentrations in Endemic Goiter in Greece

Abstract

The serum concentrations of triiodothyronine (T3) and thyrotropin (TSH) measured by radioimmunoassay, and that of thyroxine (T4), measured by competitive protein binding assay, were assessed in goitrous and nongoitrous subjects residing in an area of moderate iodine deficiency in Greece. Results were compared to those obtained in a group of age-matched control subjects residing in Boston, an area of adequate iodine intake. Serum T4 concentrations were within the normal range in both goitrous and non-goitrous Greek subjects, but were nevertheless significantly lower than in the Boston controls. Serum T3 concentrations in the nongoitrous Greek subjects were similar to those in the Boston group, but values in the goitrous Greek subjects were significantly increased. Serum TSH concentrations in the Greek subjects were, with one exception, within the normal range and were almost identical to those in the Boston controls. It is suggested that endemic iodine deficient goiter in Greece is the result of an increased sensitivity of the iodine-deficient thyroid to the stimulatory effect of TSH on thyroid size and on the secretion of T3 relative to T4.