Endocrine Abstracts

Background: Levothyroxine (LT4) is one of the most commonly prescribed drugs in the western world. Approximately half a million people of the Dutch population use LT4 therapy and are thus instructed to ingest LT4 in a fasting state. Yet, postponing breakfast seems to be challenging for many patients and appears to be an important reason for suboptimal adherence to LT4 therapy. In this study, we aimed to determine the impact on daily life of postponing breakfast in a LT4-using population in the Netherlands.

Methods: LT4-using patients who visited Zuyderland Medical Center during a 6-month-study period were invited to complete a questionnaire. Regression analyses were performed to identify factors associated with non-fasting LT4 ingestion.

Results: 410 out of 463 invited patients completed the questionnaire (88.6%). 76.8% was female and median age was 57 years [IQR:43-67]. Participants were mostly long-time LT4-users (>5 years) (60.9%). Almost all participants ingested LT4 in the morning (96.3%) of whom 68% postponed breakfast for 30-60 minutes. However, 60.5% reported to prefer ingestion of LT4 together with breakfast instead of postponing breakfast. Interestingly, 25% of the participants reported to skip their breakfast due to the fasting ingestion. While almost all participants reported they were instructed to ingest LT4 in a fasting state, only a minority reported to be aware of the recommended time interval between LT4 ingestion and interfering co-medication. Use of co-medication was associated with a higher likelihood for non-fasting LT4 ingestion (OR:2.71;95%CI:1.74-4.21;P < 0.001).

Conclusion: 60% of our study population would prefer LT4 ingestion together with breakfast and 25% reported to skip their breakfast due to the fasting ingestion. Therefore, further research on the effects of LT4 ingestion together with breakfast is warranted.