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Starting Dose of Levothyroxine for Hypothyroidism

Slow titration of levothyroxine probably is unnecessary for young adults.

When initiating treatment for primary hypothyroidism, some clinicians prescribe full replacement doses of levothyroxine, whereas others start patients on low doses and titrate upward gradually. In this randomized double-blind trial, researchers compared these approaches in 50 patients with newly diagnosed hypothyroidism (median thyroid-stimulating hormone [TSH] level, 55 mIU/L; mean free thyroxine [T₄] level, 0.6 ng/dL). Mean age was 47 (range, 22–86), and all enrollees had normal dobutamine echocardiography results and no history of cardiac disease.

Starting doses of levothyroxine were either full (1.6 µg/kg daily) or low (25 µg daily initially, and increased by 25 µg every 4 weeks until euthyroidism was achieved). Median TSH levels had normalized by 4 weeks in the full-dose group, but not until 16 weeks in the low-dose group. However, symptom and quality-of-life scores, recorded on questionnaires administered serially during 48 weeks, improved at similar rates in the groups. No adverse events were noted.

Comment: As expected, immediate dosing with full-dose levothyroxine resulted in quicker biochemical euthyroidism than did gradually titrated, low-dose therapy in this study of carefully selected hypothyroid patients. Although the full-dose strategy is probably more convenient (because fewer dose adjustments are required), it was not associated with any clinical advantages. These results — plus common sense — suggest that slow titration probably is unnecessary for young healthy patients but is prudent for older patients or those at risk for coronary ischemia.

— Allan S. Brett, MD

Published in Journal Watch General Medicine September 6, 2005

Citation(s):

Roos A et al. The starting dose of levothyroxine in primary hypothyroidism treatment: A prospective, randomized, double-blind trial. Arch Intern Med 2005 Aug 8/22; 165:1714-20.

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