Endocrine Abstracts

Background: Ramadan fasting entails abstinence of food and drink from dawn to sunset for 30 days. Medication timing also changes; for patients with hypothyroidism this can be a challenge as levothyroxine (LT4) is normally taken on an empty stomach and at least half an hour before breakfast. Complying with this advice during Ramadan is impractical for religious and social reasons. Adverse changes in thyroid function in patients with hypothyroidism have been observed. Whether and for how long these changes persist after Ramadan is unclear.

Aim: Investigate the short and long-term impact of Ramadan fasting on thyroid function of patients on thyroxine replacement therapy.

Methods: Patients with hypothyroidism who attended Imperial College London Diabetes Centre (ICLDC, Abu Dhabi) during 2012 and 2017, and were; (1) Arab-Emirati; (2) aged ≥ 18 years; (3) on LT4; (4) not diagnosed with type 1 diabetes; (5) had a thyroid function test (TFT) within 3 months before Ramadan (BR); and (6) had a TSH result ≤ 10 uIU/ml at that visit (BR), were initially included. Selected patients were then followed up to check if they had a TFT at; (1) 1–2 weeks post Ramadan (PR1); (2) 2–3 months post-Ramadan (PR2); and (3) 4–6 months post Ramadan (PR3). Mann-Whitney test was used to test for significant differences in TSH, FT3, and FT4 levels at BR, compared to PR1, PR2, and PR3.

Results: 197 had a TFT at all 4 timepoints (BR, PR1, PR2, and PR3), and were included in the analysis. 89.9% of the cohort studied were females and the mean age was 44.7 ± 12.3 years. Prevalence rates of prediabetes and type 2 diabetes were 33.5% and 9.1%, respectively. At PR1, TSH levels were significantly higher, and FT3 and FT4 levels were significantly lower, compared to BR (Figure 1). These significant differences disappeared at PR2, and PR3, where TSH levels decrease and FT3 and FT4 levels increase.

Conclusions: Ramadan fasting leads to adverse, but temporary changes in thyroid function in patients with hypothyroidism which resolve within 2–3 months after Ramadan. Further prospective studies are needed to establish appropriate timing for thyroxine ingestion during Ramadan.

Figure 1 The impact of Ramadan on thyroid function tests. Box plots demonstrating levels of (A) TSH, (B) FT4, and (C) FT3, at within 3 months before Ramadan (BR), 1–2 weeks (PR1), 2–3 months (PR2), and 4–6 months (PR3) after Ramadan.

Numbers above each boxplot represents the median. P value; Related-Samples Mann-Whitney Test.