Efficacy and Safety of Once-Weekly Thyroxine for Thyroxine-Resistant Hypothyroidism

Noncompliance with thyroxine therapy is the most common cause of poor control of hypothyroidism. An open-label prospective study to compare once-weekly thyroxine (OWT) with standard daily thyroxine (SDT) was undertaken.

Patients taking thyroxine doses of >3 μg/kg/d, with or without normalization of TSH, were included and administered directly observed OWT or nonobserved SDT according to patient preference based on their weight for 6 weeks. Furthermore, patients on OWT were advised to continue the same at home without supervision.

Twenty six of 34 patients on OWT and 7 of 18 patients on SDT achieved a TSH <10 μIU/mL (P < 0.05), and 2 patients from the SDT arm were lost to follow-up. During home treatment, 15 of 25 at 12 weeks and 19 of 23 contactable patients at a median follow-up of 25 months maintained TSH below target. Thyroxine absorption test was unable to predict normalization of TSH at 6 weeks of OWT therapy. No adverse events were seen with OWT-treated patients over the 12-week follow-up period. OWT has significantly higher efficacy (OR = 5.1) than SDT for patients with thyroxine-resistant hypothyroidism and is not associated with side effects.

OWT benefits a majority of patients in the long-term treatment of thyroxine-resistant hypothyroidism, in the real-world setting.