Reference intervals of thyroid hormones in a previously iodine-deficient area in Darfur, Sudan

Background: Thyroid-stimulating hormone (TSH), thyroxin (T4) and T3 levels are varied in the different settings with disorders of thyroid homeostasis. It is recommended that every setting has to establish its own reference intervals (RIs) for these hormones. Methods: A multi-stage stratified sampling method was used to select a representative sample of a Sudanese adult (>20 years of age) in Nyala in western Sudan in the Darfur region during the period between January and June 2016 to establish RIs of thyroid-related hormones (TSH, T4 and T3). In this study, 1753 serum samples (male and female) with different age groups were investigated. A radioimmunoassay gamma counter was used to measure the level of these hormones. Results: The median (95% intervals) of serum TSH, T4 and T3 levels was 1.2 (0.50-3.0) mIU/l, 111.0 (72.0-161.0) nmol/l and 1.5 (0.8-2.8) nmol/l respectively. While the level of TSH was significantly higher in the age group between 31 and 40 years, both T4 and T3 levels have shown a progressive increase with age. There was no significant difference in the TSH, T4 and T3 level when the RIs were compared between males and females. Conclusion: The RIs for TSH, T4 and T3 in this setting were different from the levels provided by the manufacturers. The RIs were different in the different age groups.