Effect of Puberty on Kidney Function in children with chronic kidney disease

Technical Summary: Effect of Puberty on Kidney Function in Children with Chronic Kidney Disease

Problem Statement
Chronic kidney disease (CKD) in children is a progressive condition where the transition through puberty is widely considered a critical period for kidney function deterioration. While pubertal delay is a well-recognized complication in pediatric CKD, the specific impact of pubertal physiological changes on CKD progression remains poorly understood. Existing literature has largely focused on children with advanced CKD (stages 3–5), leaving a significant gap in knowledge regarding functional decline in children with early-stage disease (CKD stages 1–2) or preserved baseline kidney function. Furthermore, previous studies have utilized various clinical markers (e.g., Tanner staging, menarche) to define pubertal timing, which may not fully capture the integrated growth-related and physiological shifts that characterize this developmental window.

Methodology
This study utilized a multicenter, prospective cohort design based on the KoreaN cohort study for Outcome in Patients With Pediatric Chronic Kidney Disease (KNOW-Ped CKD).

• Study Population: The analysis included 212 children with CKD (156 males, 56 females) who were followed for at least three years and experienced a pubertal transition during the study period. Patients with baseline CKD stage 5, peak height velocity (PHV) occurring before age 10, or insufficient follow-up data were excluded.
• Pubertal Reference Point: Puberty was objectively defined using Peak Height Velocity (PHV) as the temporal anchor, rather than clinical staging alone.
• Kidney Function Metrics: Estimated Glomerular Filtration Rate (eGFR) was assessed annually using two distinct equations to mitigate bias from pubertal muscle mass accretion:
  1. Creatinine-based eGFR (eGFRcr) using the bedside Schwartz equation.
  2. Creatinine–cystatin C–based eGFR (eGFRcr-cys) using the CKiD equation.
• Analysis: Longitudinal trajectories were evaluated by calculating annualized eGFR decline rates for two distinct periods: pre-PHV (baseline to PHV) and post-PHV (PHV to last follow-up). Subgroup analyses were conducted based on baseline CKD stage (Stage 1 vs. Stages 2–4) and sex.

Key Results

• Overall Trajectory: A significant, non-linear decline in eGFR was observed across the pubertal transition. Both eGFRcr and eGFRcr-cys declined from baseline to PHV, followed by an accelerated decline post-PHV.
  • eGFRcr: Declined by 4.40 ± 18.65 mL/min/1.73 m² pre-PHV and 17.29 ± 17.63 mL/min/1.73 m² post-PHV.
  • eGFRcr-cys: Declined by 1.81 ± 12.76 mL/min/1.73 m² pre-PHV and 11.38 ± 13.98 mL/min/1.73 m² post-PHV.
  • The post-PHV decline was statistically significant (p < 0.001) and exceeded the threshold for rapid progression (≥5 mL/min/1.73 m² annually) for both equations.
• Stratification by CKD Stage: Children with CKD Stage 1 (preserved baseline function) exhibited a substantial decline in eGFR during puberty, with the reduction being more pronounced than in children with Stages 2–4.
  • Stage 1 (eGFRcr): Declined by 13.44 ± 24.91 mL/min/1.73 m² pre-PHV and 30.46 ± 23.44 mL/min/1.73 m² post-PHV.
  • Stages 2–4 (eGFRcr): Declined by 1.39 ± 14.95 mL/min/1.73 m² pre-PHV and 12.90 ± 12.52 mL/min/1.73 m² post-PHV.
• Stratification by Sex:
  • Males: Showed a marked, continuous decline in eGFR across puberty.
  • Females: Exhibited a slight increase in eGFR from baseline to PHV, followed by a substantial decline post-PHV. However, the authors note the female sample size was relatively small, warranting caution in interpreting sex-specific differences.
• Equation Comparison: The consistent decline observed in both eGFRcr and eGFRcr-cys suggests that the deterioration is not solely an artifact of increased muscle mass affecting creatinine levels, but rather reflects a true reduction in filtration capacity.

Significance and Claims
The paper claims that puberty represents a vulnerable transition period for children with CKD, characterized by an accelerated decline in kidney function that occurs even in patients with early-stage disease and preserved baseline eGFR.

• Clinical Implication: The findings highlight the necessity for vigilant longitudinal monitoring during the pubertal transition, specifically for children with CKD stages 1–4, to promptly identify accelerated progression.
• Methodological Contribution: By anchoring the analysis to PHV, the study provides a more biologically relevant temporal alignment for assessing kidney function trajectories compared to other pubertal markers.
• Physiological Insight: The concordant decline in both creatinine-based and cystatin C-based equations suggests that the observed eGFR reduction reflects genuine physiological changes in filtration capacity, potentially driven by the convergence of rapid somatic growth, increased hemodynamic demands (hyperfiltration theory), and hormonal changes, rather than measurement bias alone.

The authors conclude that while the precise mechanisms require further investigation (noting limitations such as the lack of measured GFR and serial hormone data), the empirical evidence underscores puberty as a critical window for disease progression in pediatric CKD.