Endocrine Abstracts

Graves’ disease typically follows a relapsing and remitting course. Most patients with recurrent hyperthyroidism after withdrawal of antithyroid drugs (ATDs) are offered definitive treatment with radioactive iodine. This retrospective study aimed to identify clinical and biochemical indices that predict relapse following ATD withdrawal, which could allow earlier definitive treatment to be initiated.

We studied 70 patients with Graves’ disease who had successfully completed a minimum of 12 months ATDs and had been followed up for at least 12 months after stopping ATDs. Forty five patients (36 female) had recurrence of hyperthyroidism following ATD withdrawal (relapse group), with 71% relapsing within the first 12 months of stopping ATDs. Twenty five subjects (20 female) remained euthyroid for at least one year following ATD cessation. Subjects were of a similar age at diagnosis (median age 44y in relapse group, 39y in control group).

The presence of Graves’ ophthalmopathy did not predict relapse (P=0.5) and those who relapsed were not more likely to smoke (P=0.4). Relapse of hyperthyroidism following ATD withdrawal was not greater in those with a family history of thyroid disease (P=0.7). Although data for patient ethnicity was incomplete (n=15 for control group, n=21 for relapse group), relapse did not occur more commonly in any specific ethnic group. Patients who had relapsed following ATD withdrawal had significantly greater plasma free thyroxine (fT4) concentrations at the time of ATD withdrawal compared to controls (16.8+1.0 [relapse] vs. 14.2+0.42 pmol/l [control] P<0.05). However, both groups had similar free tri-iodothyronine and thyroid stimulating hormone concentrations on completion of ATD treatment.

These data suggest that plasma fT4 concentrations at the time of ATD withdrawal may be predictive for relapse of hyperthyroidism in Graves’ disease. However, no other specific factors predicting relapse were identified.