Long-term remission following antithyroid drug withdrawal in patients with Graves' hyperthyroidism: parameters with prognostic value

Abstract

Objective: To assess the predictive value of some clinical and biochemical parameters, and of the +49 A/G polymorphism of the CTLA-4 gene, for long-term remission following the withdrawal of antithyroid drugs before starting antithyroid drug therapy.

Study design: Observational, prospective and longitudinal study.

Methods: Seventy-two patients (11 of whom were men) with newly diagnosed Graves' hyperthyroidism who had been attended consecutively at a University Clinic in a population with sufficient iodine intake were included in the study.

Exclusion criteria: patients under the age of 18, pregnant women and non-Caucasian patients. All subjects were treated following a well-defined protocol. Long-term remission was calculated at 12 and 36 months following withdrawal of the antithyroid drug.

Results: Thirty-six of the 72 study subjects experienced a remission of at least 12 months following withdrawal of methimazole, with no differences according to their age or sex. A comparison made between the remission rates seen in both groups yielded significant differences regarding the presence of Graves' orbitopathy, the duration of the treatment with methimazole and the absence of the CTLA-4 G/G genotype. In the univariate and multivariate analyses performed, only lower frequencies of Graves' orbitopathy and an absence of the CTLA-4 G/G genotype were considered independent predictors of long-term remission.

Conclusions: The absence of Graves' orbitopathy and of the CTLA-4 G/G genotype are independent predictors of long-term remission following a first course of antithyroid drugs.

Keywords: +49A/G polymorphism of the CTLA4 gene; Graves’ hyperthyroidism; Graves’ orbitopathy; Methimazole; Predictors of remission.