Thyroid Hormone Reference Interval- Evidence from Alappuzha District, Kerala State, India

Abstract

Introduction: Thyroid diseases are one of the most common endocrine disorders not only in India, but worldwide. Most commonly done biochemical tests to diagnose thyroid disorders are Thyrotropin (TSH), thyroid hormones {free thyroxine (FT4) and free triiodothyronine (FT3)} in serum. The Reference Interval (RI) is influenced by a variety of factors like diet, genetics, iodine nutritional status and thyroid autoimmunity. Hence, the reference values of thyroid function tests commonly used in the clinical laboratories are derived from data from the western population and may not be applicable for Indian population. Aim: To establish RI for thyroid hormones in the coastal area of Alappuzha District in Kerala. Materials and Methods: This community-based study included 228 adults in the age group 18-80 years. TSH, FT3, FT4, Thyroperoxidase antibody (TPOAb) and anti- thyroglobulin antibodies (TgAb) were analysed on an automated immunoassay system Access 2 Beckman Coulter using a direct chemiluminescence detection system. RIs were calculated according to International Federation of Clinical Chemistry (IFCC) recommendation using IBM SPSS version 20.0 for windows. Results: RIs for serum TSH, FT4 and FT3 were calculated as 0.11-6.39 mIU/L, 0.58-4.66 ng/dL and 0.72-4.66 pg/mL. No significant age and gender difference in the RIs are noted. Conclusion: In this study, RI established in the local reference population found to be different from those reported by previous studies conducted in other geographical areas.