Sensitivity to Thyroid Hormones and Reduced Glomerular Filtration in Children and Adolescents with Overweight or Obesity.

Background: Reduced central sensitivity to thyroid hormones (THs) has been observed in euthyroid adults with reduced renal function. This topic is unexplored in young people with overweight or obesity (OW/OB). Objective: The aim of this study was 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, 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), TSHI (2.95 ± 0.45 vs. 2.85 ± 0.55; p = 0.031), TFQI [1.00 (0.98–1.00) versus 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.