Sensitivity to thyroid hormones and reduced glomerular filtration in children and adolescents with overweight or obesity

Background: Reduced central sensitivity to thyroid hormones (TH) has been observed in euthyroid adults with reduced renal function. This topic is unexplored in young people with overweight or obesity (OW/OB). Objective: To evaluate the association between sensitivity to TH and mild reduced estimated glomerular filtration rate (MReGFR) in euthyroid children and adolescents with OW/OB. Methods: Data of 788 euthyroid children and adolescents with OW/OB (aged 6-16 years), recruited from seven Italian centers for the care of OW/OB, were evaluated. Peripheral sensitivity to TH was estimated through the FT3/FT4 ratio, while central sensitivity was assessed by estimating TSH index (TSHI), Thyrotroph T4 Resistance Index (TT4RI), Thyroid Feedback Quantile-based Index (TFQI), Parametric Thyroid Feedback Quantile-based Index (PTFQI). MReGFR was defined by an eGFR value >= 60 and <= 90 mL/min/1.73 m2. Results: Subjects with MReGFR had significantly lower levels of FT3/FT4 ratio (0.43 +/- 0.09 vs 0.44 +/- 0.10; p=0.028) and higher levels of TSH (2.89 +/- 1.00 vs 2.68 +/- 0.99; p=0.019), TSH Index (2.95 +/- 0.45 vs 2.85 +/- 0.55; p=0.031), TFQI [1.00 (0.98-1.00) vs 1.00 (0.97-1.00); p=0.046] and PTFQI (0.66 +/- 0.17 vs 0.60 +/- 0.23; p=0.006) compared with individuals with normal eGFR. Odds ratio of MReGFR raised of 1.2-3.2-fold for each increase of 1 mIU/L in TSH, 1 unit in TSHI, and PTFQI, but not for FT3/FT4 ratio. Conclusion: MReGFR is associated with reduced indices of central sensitivity to TH in euthyroid children and adolescents with OW/OB. This preliminary observation should be confirmed in prospective studies.