CLINICAL, BIOCHEMICAL AND IMMUNOLOGICAL CHARACTERISTICS OF RELAPSERS AND NON-RELAPSERS OF THYROTOXICOSIS TREATED WITH ANTITHYROID DRUGS

Objectives. This study aims to correlate clinical, biochemical and imm unological factors seen at diagnosis of thyrotoxicosis with subsequent relapse within 5 years. Design. Retrospective review of case notes, a nd biochemical assessment at least 5 years after cessation of treatmen t. Setting, A large general hospital endocrine clinic. Subjects, Patie nts presenting with a first episode of thyrotoxicosis between 1988 and 1991 who were treated with antithyroid drugs for at least 18 months. Main outcome measures. Relapse was determined by examination of hospit al records, general practice records, patient questionnaire and thyroi d function tests. Results. A total of 216 subjects presented for the f irst time with thyrotoxicosis, of whom 89 (41.2%) suffered a relapse o f the disease. On univariate analysis, clinical factors associated wit h increased relapse include younger age at diagnosis, goitre, marked t achycardia, requirement for higher maintenance dose of carbimazole, hi gher FT4 levels at diagnosis and smoking. Factors not predictive of re lapse include presence of thyroid eye signs, positive family history, atrial fibrillation or congestive cardiac failure, acropachy or pretib ial myxoedema, and presence or absence of thyroid autoantibodies. Logi stic regression analysis showed relapse was predominantly determined b y an FT4 > 56.2 nmol L-1, pulse rate > 110, presence of goitre and a p ositive smoking history (R-2 = 0.3, P < 0.001). Presence of these four factors predicted relapse in 76 (85.4%) of the 89 patients who relaps ed. Conclusions, Increased 'toxicity' of thyrotoxicosis, goitre and sm oking are associated with relapse of thyrotoxicosis, and this may be h elpful in determining which patients may be better managed with early ablative therapy.