Context: The regulation of SHBG is complex and influenced by sex steroids and insulin. Objective: To describe serum levels and evaluate determinants of SHBG levels in healthy children, and in girls with central precocious puberty (CCP) before and during gonadotropin releasing hormone analogue (GnRHa) treatment. Design: Cross-sectional on healthy subjects, and 2-years longitudinal in girls with CPP. Setting: Tertiary referral centre for paediatric endocrinology. Participants/patients: Nine-hundred and three healthy school children served as healthy subjects. Twenty-five girls with precocious/early puberty. Interventions: Girls with CPP were treated with the long-acting GnRHa Triptorelin. Results: SHBG levels declined with increasing age in both sexes until adulthood. In healthy children, SHBG was significantly negatively correlated with Testosterone (T), Estradiol (E2), Dehydroepiandrosterone Sulphate (DHEAS) and body mass index (BMI) in boys (total model R² = 0.71), but only with DHEAS and BMI in girls (total model R² = 0.26). Body fat percentage was significantly negatively correlated with SHBG levels (P < 0.001) in both boys (R² = 0.18) and girls (R² = 0.23). Girls with CPP had significantly lower pre-treatment SHBG levels compared to age-matched controls (SHBG-SDS -1.29 [-4.48; 0.01]), which declined even further during GnRHa treatment (-2.75 [-5.9; 0.53]; P < 0.001). Even after adjustment for BMI and pubertal stage girls with CPP had lower SHBG levels (P < 0.001) compared to healthy controls. Conclusions: SHBG levels were strongly dependent on body composition and sex steroid levels in children with normal and precocious puberty. Studies on insulin sensitivity and SHBG in puberty are needed in order to better understand the interaction between body composition and gonadal maturation.