Investigating Levothyroxine Use and Its Association with Thyroid Health in Patients with Hypothyroidism: A Community Pharmacy Study

To gain maximum therapeutic effect while minimizing side effects, it is imperative for patients with hypothyroidism to use their levothyroxine (LT4) correctly, such as adhering to the prescribed regimen. Little is currently known about how patients actually use LT4 in real life. We investigated the use of LT4, as well as the thyroid health (thyrotropin [TSH] and health-related quality of life [HR-QoL]), and evaluated if proper LT4 use is associated with better thyroid health. A cross-sectional observational study was conducted in a Belgian community sample of adults using LT4 for hypothyroidism since ≥2 years. Participants completed a self-administered questionnaire on patient characteristics, self-reported adherence to LT4, timing of intake, and co-medication. They also completed the thyroid-specific patient-reported outcome (ThyPRO-39) questionnaire, measuring the HR-QoL. Pharmacy dispensing data were used to calculate the medication possession ratio (MPR). We included 856 participants (mean age 61.4 ± 14.3 years, 86% [740/856] females). Approximately one in four participants (138/563) had out-of-range TSH levels. Generally, ThyPRO-39 scores were in the lower part of the range (indicating better HR-QoL), with the scales "emotional susceptibility" and "tiredness" showing the worst scores. Approximately 28% (178/632) of the participants were classified as non-adherent (MPR