Elevated Serum Concentrations of Triiodothyronine in Hypothyroid Patients: Values for Patients Receiving USP Thyroid

• Serum concentrations of thyroxine (T 4 ), triiodothyronine (T 3 ), and thyroid-stimulating hormone (TSH) were measured for 14 hypothyroid patients while they were receiving USP desiccated thyroid and after six weeks of therapy with comparable doses of levothyroxine sodium (Na-l-thyroxine). Therapy with USP thyroid caused supraphysiologic elevations in the concentration of T 3 in 13 patients. Treatment with levothyroxine resulted in serum concentrations of T 3 that were within the range of normal. We believe the preferable therapy for hypothyroidism is levothyroxine. ( Am J Dis Child 134:16-18, 1980)