To Evaluate the Biochemical Changes that Predisposing to CVD in Subclinical Hypothyroidism

Abstract

Background: Regulation of thyroid hormones is critical to optimum growth, metabolism and organ function. Subclinical thyroidism is a common stable thyroid disorder, mostly found in middle aged and elderly population without any major symptoms. This can be of two types- subclinical hyperthyroidism and subclinical hypothyroidism.Subclinical hypothyroidism as a clinical event where serum thyroid hormones T3 and T4 are at normal respective physiological levels but serum TSH is mildly elevated. Serum TSH has a linear exponential relationship with free thyroid hormones and 2 fold changes in free T4 will lead to 100 fold changes in TSH levels. This SCH is more common in women and normally increases with age. The author further added that the most serious clinical implication of SCH is its gradual progression towards usual hypothyroidism. They added that SCH occurrence happens due to reduced iodide clearance due to impaired glomerular filtration in CKD patients. This results into an elevated plasma iodide concentration that alters thyroid functioning.
 Aim: The present study was undertaken to identify various biochemical and molecular biomarkers for the early detection of cardiovascular disease (CVD) among subjects with subclinical hypothyroidism (SCH).
 Material and Method: A case-control study layout was adopted for the present study to identify the various biochemical and molecular biomarkers for the early detection of Cardiovascular Disease among subjects with Subclinical Hypothyroidism. All test and control subjects provided their information on a well-defined proforma regarding their demographic records, family history and disease-related records. The study group included 150 clinically diagnosed individuals with subclinical hypothyroidism and 100 age and sex matched healthy control subjects. Various biochemical parameters, lipid profile, oxidative profile, inflammatory profile, renal profile and emerging biomarkers such as NT-proBNP and PAPP-A were evaluated and compared among study and control subjects.
 Results: This study provides Biochemical, investigations as well as inflammatory and oxidative risk markers along with emerging biomarker like NT-proBNP and PAPP-A showed a statistically significant difference between study subjects and control subjects. Variables like PAPP-A, Uric acid, MDA, TC, TG, TSH, Urea, weight and BMI showed a strong positive correlation with NT-proBNP concentration. Moreover, creatinine showed a positive correlation with NT-proBNP. Mean NT-proBNP, uric acid, MDA, TC, LDL, TG, TSH, Urea, creatinine, showed a strong positive correlation with PAPP-A level. HDL-C showed a negative correlation with PAPP-A concentration.
 Conclusion: Subclinical hypothyroidism is one of the most prevalent autoimmune diseases provoked in genetically susceptible individuals by several triggers, including female sex, advanced age, obesity, abnormal lipid profile and environmental factors. These risk factors seem to contribute DNA damage as indicated by increase in micronuclei frequency. SCH is often linked with higher chance for developing a wider range of adverse health outcomes and that SCH might represent a potentially modifiable risk factor of CVD. Therefore, better understanding of the pathophysiology, prevalence and the risk factors of SCH could help in the prevention of CVD in the population.
 Keywords: Malondialdehyde, Thyroid Stimulating Hormone, NT-proBNP, PAPP-A, CVD and Subclinical Hypothyroidism