Establishment of reference intervals of thyroid function test in healthy individuals

Aim: The central role of the laboratory is to aid the clinician, in interpreting observed values, by providing relevant reference values. To prevent ambiguities inherent in the term normal values, a laboratory should establish its own reference limits. Therefore, the current study was aimed at establishing the reference range of Thyroid function test in healthy population. Study design: This was a retrospective cross sectional study on 1000 healthy individuals above 18 years of age, attending the routine health check-up. Materials and Methods: Partitioning was done according to age and sex, inclusion and exclusion criteria were applied and T3, T4 and TSH levels were estimated on the study group. Results: The values of T3 and T4 obtained were (mean and reference interval in nmol/L) 1.85 (1.15-2.55) and 100.58(57.35-143.81)respectively for males and 1.87(1.07-2.55) and 110.49(62.46-158.52) respectively for females. Similarly, TSH values were 1.23 (0.37-5.19) mIU/L and 1.37(0.27-5.63) mIU/L in males and females respectively. Conclusion: We found that the value of serum Total T3 & serum Total T4 was higher as compared to the international values while that serum TSH was similar.