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Mechanisms of Antithyroidal Activity of Methimazole

1966; Elsevier BV; Volume: 55; Issue: 8 Linguagem: Inglês

10.1002/jps.2600550814

1520-6017

Robert Brock, W.F. Head,

Thyroid Disorders and Treatments

Methimazole produces a significant inhibition of iodide ion absorption by the intact thyroid which may account for the major portion of its antithyroidal action. The principal intrathyroidal effect of methimazole is shown to be due to its reactivity with elemental iodine. It neither inhibits nor serves as a competitive substrate for the hydrogen peroxide-peroxidase enzyme system. Thyroxine is displaced from its serum binding sites by methimazole; however, this mechanism is not considered to be clinically important. Methimazole produces a significant inhibition of iodide ion absorption by the intact thyroid which may account for the major portion of its antithyroidal action. The principal intrathyroidal effect of methimazole is shown to be due to its reactivity with elemental iodine. It neither inhibits nor serves as a competitive substrate for the hydrogen peroxide-peroxidase enzyme system. Thyroxine is displaced from its serum binding sites by methimazole; however, this mechanism is not considered to be clinically important.