Euthyroidism and Cardiovascular Disturbances

Introduction: The immunoassay of TSHus is the first-line biological examination in case of suspected dysthyroidism. It is important to define the reference intervals in each medical biology laboratory according to their reference population and the analytical method used for an accurate interpretation of the biological results. There is now a consensus around the reference interval 0.4 to 4.0 mIU/l for TSH. However, the upper limit is a source of divergent opinions. Several learned societies, based on several solid studies, believe that this value should be lowered. Indeed, by analyzing the cardio-metabolic status within the so-called euthyroid population, it turned out that people with TSH > 2.5 mIU/l presented a higher cardiovascular risk than those with TSH below this value. Objective: This study has two complementary objectives: The first consists of validating the reference values of TSHus by electrochemiluminescence (ECLIA) on COBAS e411, the second is the study of the prevalence of cardiovascular risk factors within a euthyroid population as a function of TSHus. Materials and methods: This is a comparative prospective study conducted at the central biology laboratory (biochemistry unit) of the CHU Bab El Oued on a population of 125 euthyroid patients (TSHus between 0.27 and 4.2 mIU /I). Study patients were subdivided into two groups: group 1 with TSH < 2.5 mIU/L and group 2 with TSH ≥ 2.5 mIU/L. The clinical and anthropometric data were all compiled on an information sheet and a complete biochemical assessment was carried out for all the patients in the study. Result: The reference values proposed by the reagent manufacturers have been validated according to the CLSIEP28-A3c protocol. Also the comparison of cardiovascular risk factors between the two groups revealed that their prevalence as well as the prevalence of the metabolic syndrome were significantly higher in group 2 compared to group 1. Conclusion: Although the TSHus reference values between 0.27 and 4.2 mIU/l are validated, it seems very clear that values above 2.5 mIU/l are significantly associated with cardiovascular risk.