OBJECTIVES: Adherence to levothyroxine hormone replacement therapy is essential for the effective management of hypothyroidism. The aim of this study was to conduct a systematic review and meta-analysis on the prevalence and associated factors of poor adherence to levothyroxine in patients with hypothyroidism.

METHODS: This is a systematic review and meta-analysis of studies on the prevalence of poor therapeutic adherence in patients with hypothyroidism. All scientific literature published up to June 30, 2023, was considered. The databases consulted were PubMed, Scopus, ScienceDirect, and Google Scholar. The meta-analysis was conducted using the "Metafor" function of the "Meta" package version 4.14-0 of R software 4.2.1 for Windows.

RESULTS: A total of 23 studies were selected. The main findings of this study indicate a variable prevalence of poor adherence to levothyroxine therapy in patients with hypothyroidism, ranging from 1.9% to 94.7%. The meta-analysis provides a combined estimate of the prevalence of poor therapeutic adherence of 27% (95% CI: 17-40%) with a random effects model. The identification of factors associated with poor adherence to levothyroxine reveals several important determinants. Forgetfulness and memory problems, difficulties accessing medications, side effects, lack of information about the disease, female gender, comorbidities, and polypharmacy were identified as the main factors influencing poor adherence to levothyroxine.

CONCLUSIONS: This systematic review and meta-analysis highlights a considerable prevalence of poor adherence to levothyroxine in patients with hypothyroidism. A better understanding of this phenomenon will enable the development of targeted strategies to improve therapeutic adherence and optimize clinical outcomes in these patients. Identifying the factors associated with poor adherence allows for better targeting of interventions aimed at improving adherence and optimizing therapeutic outcomes in patients with hypothyroidism.