BMI increase during early childhood in boys with cystic fibrosis and early adrenarche

Background: Increase in body mass index (BMI) in early childhood (1−6 years) was found to be a contributing factor for impaired final height in boys with Cystic Fibrosis (CF). Early adrenarche (before age 9 years in boys) may contribute to an impaired final height by triggering an early acceleration of bone age resulting in a compromised growth spurt during puberty. We aimed to analyze the timing of adrenarche in boys with CF and to associate BMI increase in early childhood to timing of adrenarche. Methods: Boys with CF, aged 8−9 years, visiting the CF expertize center Utrecht were included. Since 2018, anthropomorphic, pubertal and endocrine data were collected. Early adrenarche in boys was defined as a dehydroepiandrosterone sulfate (DHEAS) ≥ 1 µmol/L before the age of 9 years. Results: Thirteen boys (mean age 8.55 ± 0.27 years) were enrolled. The median (IQR) DHEAS-level was 1.3 µmol/L (0.71−2.40). Eight boys (61.5%) had an early rise in DHEAS-levels ≥ 1 µmol/L. Mean increase in BMI Z-score between 1 and 6 years of age (ΔBMI₁₋₆) was −0.07 ± 0.86. A significant correlation was found between ΔBMI₁₋₆ and DHEAS-levels at the age of 8−9 years (r = 0.624, p = 0.040). In five boys with early rise in DHEAS, accelerated bone age was found (average 1.55 ± 0.96 years). Conclusion: In this small cohort, 61.5% of boys with CF between 8 and 9 years had an early rise of DHEAS, which was correlated to ΔBMI₁₋₆ between 1 and 6 years. Early adrenarche may be caused by ΔBMI₁₋₆.