Serum FT4 / FT3 Ratio, a Predictive Biochemical Marker for Subclinical Hypothyroidism in Patients with Chronic Kidney Disease.

Subclinical hypothyroidism (ScHt) is an early stage of hypothyroidism which can progress to overt hypothyroidism and lead to adverse metabolic abnormalities. Surge in frequency of hypothyroidism is seen in chronic kidney disease (CKD) cases, including those receiving dialysis. Many studies reported the relation amid thyroid function with metabolic syndrome, though the link among the Free T3: Free T4 and ScHt is not clearly determined. We wanted to investigate the Free T3:Free T4 ratio in predicting ScHt in CKD. MethodsIn this study, 53 known CKD subjects who have not undergone haemodialysis and 60 normal healthy subjects were included. In both study groups, creatinine and estimated glomerulus filtration rate (eGFR) are determined to evaluate the kidney function. Thyroid function parameters namely serum FT3, FT4 and TSH were measured to determine the FT3 / FT4 ratio. ResultsTSH levels were significantly increased in patients with CKD not undergoing dialysis as compared to patients in the control group (P<0.034). Low Free T3 level (P<0.001) and FT3 / FT4 ratio is highly significant (P< 0.001) in study subjects as compared to controls. Area Under the Curve (AUC) of ROC for the continuous variables of serum FT4 / FT3 ratio was 0.914 with CI: 0.832 to 0.997. ConclusionsIndividually FT3, FT4 have very little sensitivity in the diagnosis of sub clinical hypothyroidism in chronic kidney disease. FT4/FT3 ratio determination is a very useful step in diagnosing ScHt with chronic kidney disease.