Serum Creatinine and Uric Acid Levels in Hypothyroid Patients : A Cross Sectional Study

Background: Hypothyroidism is associated with many biochemical abnormalities including increased serum creatinine and uric acid levels. Many studies were done abroad regarding serum creatinine and uric acid levels in hypothyroid patients. We designed this study in our population for evaluation of serum creatinine and uric acid levels in hypothyroid patients. Objective: To assess serum creatinine and uric acid levels in hypothyroid patients and to find out relationship of creatinine and uric acid levels with severity of hypothyroidism. Materials and Methods: This retrospective cross sectional study to evaluate the serum creatinine and uric acid levels of hypothyroid patients and to find out relationship of hyperuricemia and hypercreatininemia with severity of hypothyroidism was done in the department of Biochemistry, Bangabandhu Sheikh Mujib Medical University, Dhaka. Results were compared with that of age and sex matched healthy euthyroid controls. Statistical analyses were performed by using SPSS for Windows version 10.0. ANOVA and unpaired ‘t’ tests were done to see the significance among the groups and between groups respectively. Pearson’s correlation coefficient test was done to see the correlation of serum creatinine and uric acid levels with the severity of hypothyroidism. Results: Mean serum creatinine and uric acid levels in cases were 1.38 ± 0.53 and 7.00 ± 2.54 mg/dL respectively compared to 1.01 ± 0.17 and 5.21 ± 1.35 mg/dL in controls. Conclusion: Mean serum creatinine and uric acid levels were found significantly higher in hypothyroid patients compared to controls. These findings suggest that hyperuricemia and hypercreatininemia are associated with hypothyroidism. Therefore, patients presenting with these biochemical abnormalities are recommended to be investigated to explore hypothyroidism.


Serum Creatinine and Uric Acid Levels in Hypothyroid
Patients: A Cross Sectional Study hypothyroidism is a common disorder with a prevalence rate up to 20%.In another cross-sectional study on twelve hundred and twelve subjects of both sexes and age 20-60 years, the incidence of subclinical hypothyroidism was 19.7%. 6pothyroidism is associated with many biochemical abnormalities including increased serum creatinine and uric acid levels.The serum creatinine concentration increases in hypothyroid patients due to reduction of glomerular filtration rate because of hemodynamic changes in severe hypothyroidism. 7erum creatinine level may also be increased due to hypothyroid myopathy.Hypothyroidism, although rare, has been reported as a definite and authentic cause of rhabdomyolysis.As a result, hypothyroidism must be considered in patients presenting with acute renal failure and elevated muscle enzymes. 8There is high prevalence of hyperuricemia and gout in hypothyroidism.In hypothyroidism the hyperuricemia is secondary to a decreased renal plasma flow and impaired glomerular filtration. 9oraki & Basani 10 reported a case of a young male hypothyroid patient with an elevated serum creatinine level (2.3 mg/dL), markedly elevated TSH level, severe hypercholesterolemia, hyperuricemia, and a creatinine clearance of 58 mL/minute.The patient started on levothyroxine supplementation and six weeks after thyroid replacement therapy his serum creatnine had declined to 1.4 mg/dL with an estimated creatinine clearance rate of 65 mL/minute.This was accompanied by reduction in serum uric acid and cholesterol levels.Eighteen months later his creatinine had further declined to 1.0 mg/dL.
As hypothyroidism is associated with many biochemical abnormalities, it is of paramount clinical importance to have proper knowledge of these abnormalities and accurate estimation of these biochemical parameters is very important and useful for clinical management of the patients.
Many studies were done to assess serum creatinine and uric acid levels of hypothyroid patients.But, as far we know, no such study was done in our population.So, we designed this study in our population for evaluation of serum creatinine and uric acid levels in hypothyroid patients and that might be helpful for clinical management of hypothyroid patients with hyperuricemia and hypercreatininemia.

Statistical analysis
Statistical analyses were performed by using SPSS for Windows version 10.0.Mean values of the findings were compared among and between groups.
Analyses of variance (ANOVA) test and unpaired 't' test were done to see the significance among the groups and between groups respectively.Pearson's correlation coefficient test was done to see the correlation of serum creatinine and uric acid levels with the severity of hypothyroidism.'p' values <0.05 were considered significant.

Results
Table I shows the comparison of the serum creatinine and uric acid levels between the cases and the controls.Mean serum creatinine and uric acid levels in cases were 1.38 ± 0.53 and 7.00 ± 2.54 mg/dL respectively compared to 1.01 ± 0.17 and 5.21 ± 1.35 mg/dL in controls.Mean serum creatinine and uric acid levels were significantly increased in cases as compared to controls.

Discussion
In this study, mean serum creatinine value in cases was found significantly higher than in the control subjects.This finding is consistent with the previous studies done by other investigators. 7,10M e an serum creatinine level in hypothyroid cases was found significantly greater in comparison to euthyroid value in a study done by Kreisman & Hennessey. 11 In another study on 14 newly diagnosed hypothyroid patients in Switzerland mean serum creatinine level was found elevated and decreased after thyroxine replacement therapy. 12In our study, serum creatinine values were found gradually increased from Group A to Group C.An apparent positive correlation was found between serum creatinine levels of different groups and severity of hypothyroidism, but it was not significant statistically.
In the present study mean serum uric acid level in hypothyroid subjects was significantly higher than in control subjects.This finding is consistent with the studies done by other investigators.They have also found serum uric acid level significantly elevated in hypothyroid patients. 6,9,13,14In a study on 12 (twelve) induced hypothyroid rabbits, mean serum uric acid level was found higher in hypothyroid condition than in euthyroid condition. 15In our study, serum uric acid levels in Group A, Group B and Group C showed no difference and no correlation was found between serum uric acid levels and severity of hypothyroidism.
In our study, serum creatinine level was found significantly higher in hypothyroid patients.As the patients with chronic kidney diseases were excluded from the study and as our findings are consistent with some other studies, hypothyroidism should be taken into account in patients presenting with the biochemical abnormalities of chronic kidney diseases.Results of our study also suggest the findings of hyperuricemia in hypothyroid patients.Therefore, patients presenting with these biochemical abnormalities are recommended to be investigated to explore hypothyroidism.As our sample size was

Table I :
Serum creatinine and uric acid levels of study subjects