THE SIGNIFICANCE OF THE INITIAL FT4‐INDEX FOR THE MANAGEMENT OF SINGLE DAILY DOSE METHIMAZOLE TREATMENT OF HYPERTHYROIDISM

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Abstract
Since the effectiveness of 30 mg methimazole in a single daily dose in gaining initial control of hyperthyroidism may depend largely on patient characteristics, 52 patients (34 with diffuse and 18 with nodular goitre) were investigated in an attempt to determine the relative importance of a number of pretreatment variables. Return to normal thyroid hormone levels after 2 to 6 weeks of treatment appeared to be the rule, although eight of these patients formed notable exceptions (6‐20 weeks). The individual duration of treatment until achievement of biochemical euthyroidism correlated with the initial free thyroxine index (r= 0.75, Pr= 0.70, P< 0.001). For patients with a diffuse goitre it was also related to the thyroid volume estimated by ultrasound (r= 0.73, P< 0.001). According to multiple linear regression analysis however these variables were found to have no independent prognostic value. The decrease in thyroid volume during initial therapy, the nature of the goitre, a medication compliance score and various other patient variables did not correlate with the effect of treatment. In 12 cases perchlorate discharge tests were performed. The results suggest continued hormone synthesis in patients with highly active iodine trapping as an important mechanism of the postponed attainment of euthyroidism.