To the Editor.
—The oral hypoglycemic agents, the sulfonylurea compounds, are used by many physicians in the treatment of patients with insulinindependent diabetes mellitus. In addition to the well-known hypoglycemic actions of the sulfonylurea compounds, they also exert a less-recognized antithyroid activity similar to propylthiouracil.1-3 This antithyroid activity of the sulfonylurea compounds is much weaker in comparison to propylthiouracil, and, in the usual therapeutic range, patients receiving sulfonylurea compounds do not manifest a hypothyroid state.2,4 However, Hunton et al5 have found a high incidence of hypothyroidism in their diabetic population receiving sulfonylurea compounds. Little is known about the antithyroid action of sulfonylurea compounds in diabetic patients with hyperthyroidism. Brown and Solomon6 reported that carbutamide had no effect on thyroid function in two patients with hyperthyroidism. A patient with diabetes mellitus and hyperthyroidism had normal thyroid study results induced by chlorpropamide.
Report of a Case.
Tsou JY, Kotler M, Lavine RL. Thyroid-Blocking Activity of Chlorpropamide in a Diabetic Patient With Hyperthyroidism. Arch Intern Med. 1981;141(5):690-691. doi:10.1001/archinte.1981.00340050136035