[Changes in plasma fibronectin levels in patients with thyroid disease and its mechanism]

Plasma fibronectin (FN) level was determined in normal subjects and patients with thyroid disease by the Laurell method. In vitro effect of triiodothyronine (T3) on FN synthesis by cultured human fetal skin fibroblasts was also studied. Plasma FN level was 32.2 +/- 5.5 mg/dl (mean +/- SD) in normal adults, and no sex difference was observed. The plasma FN concentrations were increased in patients with hyperthyroidism (63.3 +/- 15.2 mg/dl), decreased in patients with hypothyroidism (19.5 +/- 6.5 mg/dl), and in normal range in patients with simple goiter (30.2 +/- 7.0 mg/dl). These FN values have been normalized with a time lag of a short period after their thyroid function became normal. There was a positive correlation between plasma FN concentrations and serum T3 or T4 concentrations, but a inverse correlation between plasma FN concentrations and serum thyroxine binding globulin or cholesterol levels. In vitro studies revealed that the addition of T3 to the incubation medium stimulated FN synthesis by human fetal skin fibroblasts at the concentrations between 10(-8)M and 10(-6)M. These results indicate the usefulness of plasma FN determination in patients with thyroid disease for their management and studying pathophysiology of the disease, and suggest at the fluctuation of plasma FN concentrations in these patients may at least in part due to the effect of thyroid hormone on FN synthesis by the cells.