Assessing Thyroid Function (FT4, FT3, and TSH) in Pediatric Renal Patients: A Focus on Sex and Age Subgroups.

Background: Thyroid dysfunction is a common complication but is less diagnosed most times with pediatric chronic kidney disease (CKD), where impaired renal function disrupts thyroid hormone metabolism. This study is aimed at assessing thyroid function specifically FT4, FT3, and TSH in pediatric CKD patients, while exploring variations by age and sex. Methodology: In a cross-sectional design, 150 children within the ages of 1-18 years with CKD stages 2-5 or on renal replacement therapy were examined using standardized immunoassays and eGFR determined via the Schwartz formula. Results: The results showed a 25% prevalence of hypothyroidism, with females exhibiting higher dysfunction rates than males. With age, FT4 and FT3 levels increased from infancy to adolescence, while TSH decreased, reflecting a maturing hypothalamic-pituitary-thyroid axis. Significantly, strong positive correlations were observed between eGFR and both FT3 (r = 0.78) and FT4 (r = 0.76), whereas TSH showed no notable relationship with kidney function. Conclusion: These findings suggest that thyroid dysfunction in pediatric CKD is primarily caused by decreasing FT3 and FT4 levels. Early, tailored thyroid screening is recommended to improve growth, neurodevelopment, and overall outcomes in this vulnerable population.