Discontinuation of Levothyroxine in Adults Aged 60 Years or Older

Many adults aged 60 years or older take the thyroid hormone levothyroxine, which is generally continued for life. However, it is uncertain whether long-term continuation is always necessary.

To determine the percentage of adults aged 60 years or older who can successfully discontinue levothyroxine treatment.

This single-group, prospective study included community-dwelling adults aged 60 years or older who were taking levothyroxine at a stable dosage (≤150 µg/d) for at least 1 year and had a thyrotropin (TSH) level of less than 10 mIU/L. The study was conducted at 58 general practices in the Netherlands. Participants were enrolled between January 2020 and July 2022 and final follow-up occurred on December 12, 2023.

Open-label, protocol-driven, stepwise dose reduction with thyroid function testing performed at least 6 weeks after each reduction in levothyroxine dose.

The primary outcome was the proportion of participants who discontinued levothyroxine and had both a thyrotropin level of less than 10 mIU/L and a free thyroxine level within the reference range at 1 year after the start of discontinuation. The secondary outcomes included factors associated with successful discontinuation (demographics, thyroid function, dose) and thyroid-related quality of life.

Of the 370 participants who started the levothyroxine discontinuation phase (median age, 70 [range, 60-89] years; 80% female; median thyrotropin level, 2.2 [range, 0.02-9.69] mIU/L; mean free thyroxine level, 1.21 [SD, 0.18] ng/dL), 366 completed final follow-up at 1 year. Of the 370 participants (median levothyroxine dose at baseline, 50 [range, 12.5-150] µg/d), 95 (25.7% [95% CI, 21.5%-30.4%]) successfully stopped taking levothyroxine and had a median thyrotropin level of 5.03 mIU/L (range, 1.56-9.40 mIU/L) and a mean free thyroxine level of 1.01 ng/dL (range, 0.80-1.43 ng/dL) at 1 year. Of the 95 participants who successfully discontinued levothyroxine, 46 (48.4% [95% CI, 38.6%-58.3%]) had a thyrotropin level of less than 4.8 mIU/L. Among the 88 participants taking a levothyroxine dose of 50 µg/d or lower, 56 (63.6%) successfully discontinued this treatment. Thyroid-related quality of life showed no clinically relevant changes overall from baseline to 1 year and stratified by successful levothyroxine discontinuation vs unsuccessful discontinuation.

In this open-label, single-group prospective study, 25.7% of adults aged 60 years or older discontinued levothyroxine treatment while maintaining adequate thyroid function at 1 year. Evaluation of the need to continue levothyroxine should be considered in adults aged 60 years or older, particularly in those taking a dose of 50 µg/d or lower.