Renal Function Trajectories in Chronic Kidney Disease Patients With and Without Coexisting Hypothyroidism: A Prospective Observational Study from a Tertiary Care Nephrology Centre in South India

Abstract

Background: Hypothyroidism is a common but often under-recognised comorbidity in chronic kidney disease (CKD), and the two conditions are thought to influence one another through a bidirectional axis involving renal clearance of thyroid hormone and thyroid-dependent renal haemodynamics. Prospective data comparing renal function trajectories in CKD patients with and without hypothyroidism remain limited, particularly from South Asian nephrology settings.
Methods: In this prospective observational study conducted in the Nephrology department of a tertiary care hospital, 150 patients with CKD stage 3b-5 were enrolled and assigned to Arm A (CKD alone, n = 110) or Arm B (CKD with hypothyroidism, n = 40) according to their diagnosis at screening. Serum creatinine, urea, blood urea nitrogen (BUN), estimated glomerular filtration rate (eGFR), sodium, potassium and chloride were recorded at baseline and at three further visits spaced 28 ± 3 days apart over a 12-week follow-up. Between-arm comparisons used the unpaired t-test and chi-square test, within-arm change over time used repeated-measures one-way ANOVA, and associations with thyroid-stimulating hormone (TSH) and free thyroxine (T4) were assessed with the Pearson correlation coefficient. Significance was set at p < 0.05.
Results: Mean serum creatinine rose from 6.4 ± 1.5 mg/dL at baseline to 7.9 ± 2.3 mg/dL at week 12 in Arm B, while Arm A showed a modest decline from 6.2 ± 3.5 to 5.6 ± 3.4 mg/dL (within-arm p = 0.0004 and p = 0.0483, respectively). Mean eGFR fell from 9.3 ± 2.4 to 7.6 ± 2.4 mL/min/1.73m² in Arm B (p = 0.0002) but was essentially unchanged in Arm A (15.2 ± 12.3 to 15.6 ± 10.4 mL/min/1.73m², p = 0.1839). Between-arm differences in creatinine and eGFR reached significance by the second and third visits (p ≤ 0.02 for both). Correlations between renal parameters and TSH or free T4 were weak and not statistically significant in either arm (all |r| < 0.16, p > 0.10).
Conclusion: Over a 12-week observation period, CKD patients with coexisting hypothyroidism showed a less favourable renal trajectory than those with CKD alone, despite the absence of a significant linear correlation between renal indices and circulating thyroid hormone levels. These findings support closer biochemical monitoring of thyroid status in patients with stage 3b-5 CKD, though the observational design and modest, unevenly sized comparison groups mean the results should be interpreted as hypothesis-generating rather than confirmatory.