Official Journals By StatPerson Publication
Table of Content - Volume 4 Issue 2 - November 2017
Study of uric acid, oxidative stress and antioxidant status in hypothyroidism and hyperthyroidism patients
Gurupavan Kumar Ganta1, G S R Kedari2*, H Ashwin Raj3
1Assistant Professor, 2Professor, 3Tutor, Department of Biochemistry, Saveetha Medical College, Saveetha University, Thandalam, Chennai-602105, Tamil Nadu, INDIA. Email: gurupawankumar1988@gmail.com, kedari.gsr@gmail.com, ashwinbio4@gmail.com
Abstract Thyroid disorders are more common disorders in India and worldwide. The aim of our present study was to estimate the levels of uric acid, the role of oxidative stress by assessing plasma malondialdehyde (MDA) levels and antioxidant status by estimating the levels of reduced Glutathione (GSH) and Vitamin-C (Ascorbic acid) in hypothyroid and hyperthyroid cases when compared with controls. For this, 50 diagnosed cases of hypothyroid and 50 hyperthyroid cases were included for the study. The findings were compared with 50 age and sex matched controls. A significant increase in the levels of uric acid in hypothyroid cases was observed and no statistical difference was observed between hyperthyroid cases and controls. Statistically significant increase in the levels of MDA and statistically significant decrease in the levels of reduced glutathione (GSH) and Ascorbic acid levels were observed in hypothyroid cases and hyperthyroid cases when compared with controls. Key Words: Anti-oxidant status, Oxidative stress and Uric acid.
Uric acid is a non-protein nitrogenous (NPN) substance formed during purine catabolism. Uric acid more than 6mg/dl in females and more than 7mg/dl in males is termed as hyperuricaemia. Hyperuricaemia over a period of time leads to deposition of monosodium urate crystals in the joints and surrounding tissues leading to gouty arthritis1. The global burden of Gout is substantial and seems to be increasing in many parts of the world over the past 50years. Endocrine disorders are common among Indian population out of which thyroid disorders represents an important subset of these endocrine disorders. Thyroid disorders hypo and hyperthyroidism are associated with alterations in metabolism of various substances including uric acid. Many studies showed the association between hypothyroidism and hyperuricaemia2,3 and the association between hyperthyroidism and hyperuricaemia has been controversial. A lot of studies have been done to prove the association between uric acid levels and thyroid disorders. But most of these studies have been done in the western population and north Indians. Uric acid levels have been shown to vary with ethnicity2,3. In normal cell, there is an appropriate pro-oxidant-antioxidant balance. This balance is shifted towards pro-oxidants when the production of oxygen species is increased or the levels of the antioxidants are decreased and this state is called as ‘oxidative stress’. Oxidative stress is implicated in the pathogenesis of variety of human diseases4. Oxidative damage occurs to biomolecules like lipids, proteins, carbohydrates and nucleic acids and other extracellular components like collagen and hyaluronic acid which are very deleterious5. The formation of lipid peroxides by action of free radicals on unsaturated fatty acids has been implicated in the pathogenesis of atherosclerosis and vascular diseases6. The body’s defense mechanism plays an important role in the form of antioxidants that help to minimize the damages which are caused by oxidative stress. Antioxidants are compounds that dispose, scavenge and suppress the formation of free radicals or oppose their actions7. Hence, the present study was undertaken to assess the uric acid levels, the extent of lipid per-oxidation and the status of the antioxidant defense mechanisms in patients of hypo and hyper thyroidism.
MATERIALS AND METHODS The present study was conducted in the department of biochemistry, Saveetha medical college, Thandalam. 50 newly diagnosed cases of hyperthyroidism and 50diagnosedcases of hypothyroidism were chosen for the study, which belong to the age group of 25-50years. 50 age matched and sex matched without any thyroid disorders were taken as controls. Subjects with known cases of diabetes mellitus, hypertension, renal disorders, rheumatoid arthritis, gout, smoking, alcoholism, patients taking allopurinol and probenecid were excluded from study. Informed consent was obtained from all of them.10ml of fasting blood samples were collected, the separated serum was used to estimate serum uric acid levels. Uric acid is estimated by uricase enzymatic method (uricaseand per-oxidase) method in clinical biochemistry laboratory. The plasma MDA levels were estimated by using thiobarbituric acid reacting substance (TBARS) by the method Yagi8 and Sinnhuber et al9. Reduced glutathione was determined by the method of Beutler et al10 and ascorbic acid was determined by the method of Tietz11. All the results were expressed as ±SD and statistical comparisons were done. Due permission was obtained from the institutional ethics committee prior to the starting of the work.
RESULTS
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DISCUSSION In our present study, there is statistical significant difference in the levels of uric acid in hypothyroid cases when compared with controls and no statistical significant difference was observed in the levels of uric acid in hyperthyroid cases when compared with controls. Statistical significant difference were observed in the levels of MDA, reduced glutathione and Vitamin-C levels between hypothyroid cases and controls and also hyperthyroid cases and controls. In the present study, there is statistical significance increase in uric acid levels in hypothyroid cases when compared with euthyroid subjects, this fact suggests that hypothyroid in hyperuricemia is secondary to a reduction in renal plasma flow and glomerular filtration12,13 secondary to thyroid hormone deficiency. Our study supports the studies where correlation between hypothyroidism and hyperuricaemia is well established.(14,15,16). In present study no statistical association is observed in uric acid levels between hyperthyroid and normal controls. Our study is in association with some studies17 which showed no correlation in uric acid levels and contrary to some studies18,19 which showed statistical association between hyperthyroid cases and euthyroid controls showing that hyperthyroidism can cause hyperuricaemia through the increase of purine nucleotide turnover and decrease of renal urate excretion. Our results showed that the MDA levels, an index of lipid peroxidation and reduced glutathione and vitamin –C levels of antioxidant status were modified in hypothyroidism and hyperthyroidism when compared with controls, indicates oxidative stress in hypothyroid and hyperthyroid cases. Our results are in agreement with some authors, who observed that there is significant alteration of plasma TBARS in hypothyroidism when compared to euthyroid subjects.20,21. However, other authors observed that TBARS is not altered in subclinicalhypothyroidism cases compared to Euthyroid subjects.22 Oxygen free radicals plays an important role in the pathogenesis of several conditions including hypothyroidism and hyperthyroidism23,24,25. Some authors suggest that tissues may be protected from oxidant damage because of a hypometabolic state in hypothyroidism26, whereas some other studies suggest that oxidative stress is increased in hypothyroidism27. ROS can attack double bonds in PUFA, and thus include lipid per-oxidation; this in turn results in more oxidative damage26. Similar to our studies some authors found increased markers of Oxidative stress in patients with graves disease which leads to hyperthyroid state.28 and thyroid antibodies may be seen in various disorders like type-1 diabetes mellitus29. Our study shows oxidative stress is implicated in the pathogenesis of hypothyroidism and hyperthyroidism and extensive studies are required to reduce the morbidity in these cases.
REFERENCES
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