Antithyroid effect of chlorpropamide?

The relationship between plasma chlorpropamide concentration and thyroid function was examined in 87 maturity onset diabetic patients receiving chronic therapy. Although plasma chlorpropamide concentration was weakly negatively correlated with serum thyroxine (r=0.33, p<0.01) the mean serum thyroxine and thyrotrophin (TSH) were not different from that of a matched control group of diabetics treated with diet alone. Serum thyroxine was negatively correlated with the duration of diabetes in both groups. These results suggest that chlorpropamide does not have a clinically significant antithyroid effect.