Background: Levothyroxine (LT4) is one of the most commonly prescribed medications. Although considered a life-long replacement therapy, LT4 therapy can be discontinued for some patients. This study aims at: (i) reviewing the evidence on clinical outcomes of patients undergoing thyroid hormone replacement discontinuation, (ii) identifying the predictors of successful discontinuation, and (iii) systematically appraising frameworks used for deprescribing thyroid hormone. Methods: We searched multiple bibliographic databases, including Ovid MEDLINE(R) and Epub Ahead of Print, In-Process & Other Non-Indexed Citations and Daily, Ovid Embase, Ovid Cochrane Central Register of Controlled Trials, Ovid Cochrane Database of Systematic Reviews, and Scopus, from inception to February 2020 for studies in which thyroid hormone replacement was discontinued. Clinical outcomes assessed included: proportion of patients that remained euthyroid or needed to restart thyroid hormone replacement after discontinuation and frequency of clinical symptoms of hypothyroidism and adverse effects. We also evaluated predictors for discontinuation and deprescribing frameworks. Reviewers (F.J.K.T., N.B., N.M.S.O., S.M.) evaluated studies for inclusion, extracted data, and assessed methodological quality independently and in duplicate. Results: Seventeen observational studies at moderate to high risk of bias met inclusion criteria, including a total of 1103 patients (86% women) with an age range of 2-81 years. Approximately a third of patients undergoing thyroid hormone discontinuation remained euthyroid at follow-up (37.2%, 95% confidence interval [CI 24.2-50.1%], I2 97.5%). Subgroup analysis showed that patients with a previous diagnosis of overt hypothyroidism (OH) were less likely to remain euthyroid (11.8% [CI 0.4-23.2%], I2 90.3%) than patients with a prior diagnosis of subclinical hypothyroidism (SCH) (35.6% [CI 8.2-62.9%], I2 94.0%). No study followed a framework for systematically deprescribing LT4. Conclusions: Low-quality evidence suggests that up to a third of patients remained euthyroid after thyroid hormone discontinuation, with a higher proportion of patients with an initial diagnosis of SCH remaining euthyroid than patients with an initial diagnosis of OH. A deprescribing framework focusing on adequate selection of patients for deprescribing LT4 and a systematic process is warranted to guide clinicians in re-evaluating the need for LT4 in their patients.
Keywords: deprescribing; levothyroxine; medication withdrawal; subclinical hypothyroidism; thyroid dysfunction.