Thyroxine replacement therapy: prescribing patterns and problems in 2710 patients. Scottish Automated Follow-up Register Group.

The use of thyroxine replacement therapy was studied in 2710 patients with a previous diagnosis of either thyrotoxicosis or primary hypothyroidism. The patients, who were treated in five centres, were followed-up continuously using an automated register. Seventy per cent of patients had been prescribed daily doses of thyroxine of 200 microgram or more. The estimated 10-year cumulative incidence of detected undertreatment was 13 . 2% (95% confidence limits 10 . 9-15 .6%). The median cumulative incidence of recognised overtreatment was 6 . 2%. Improved patient education and the dissemination of guidelines to doctors on the use of thyroxine replacement may reduce the incidence of undertreatment or overtreatment.