Tehran University of Medical Sciences Acta Biochimica Iranica 0001-5261 2026 4 2026 06 20 106 111 Masoume Aliabadi Iran University of Medical Sciences Mohammadreza Azadi Pourghahestani Iran University of Medical Sciences Mitra Nourbakhsh Department of Clinical Biochemistry, School of Medicine, Iran University of Medical Sciences, Tehran, Iran. Maryam Razzaghy-Azar Hazrat Aliasghar Children's Hospital, School of Medicine, Iran University of Medical Sciences. Tehran, Iran. Mona Nourbakhsh Hazrat Aliasghar Children's Hospital, School of Medicine, Iran University of Medical Sciences. Tehran, Iran. 2026 06 13 2026 07 25 Objective: Precocious puberty is a significant pediatric endocrine disorder with potential long-term physical and psychosocial consequences, including short stature, obesity, and increased risk of certain malignancies. Vitamin D (vitD) has been proposed to play a role in reproductive maturation. However, the evidence regarding its association with precocious puberty remains inconsistent across populations. This study aimed to investigate the relationship between serum vitD levels and idiopathic central precocious puberty (ICPP) in Iranian girls. Methods: This case-control study included 81 girls diagnosed with central precocious puberty and 51 healthy girls as controls. Demographic, anthropometric, and laboratory data (including age, weight, height, and serum levels of estradiol, LH, FSH, TSH, T4, and 25-hydroxyvitamin D) were extracted from clinical records. BMI z-scores, weight-for-age z-scores, and weight-for-height z-scores were calculated using standardized tools. Serum vitD levels were compared between groups, and correlations with anthropometric and biochemical parameters were assessed using appropriate statistical tests. Results: Median serum vitD levels were significantly lower in the case group than in controls (27.05 vs. 41.00 ng/mL; P = 0.0006). BMI z-score and weight-for-age z-score were significantly higher in girls with precocious puberty (P < 0.0001). Cases showed a larger discrepancy between bone age and chronological age (P < 0.0001). Serum vitD showed significant inverse correlations with BMI z-score (r = −0.236, P = 0.035) and weight-for-height z-score (r=−0.605, P=0.028), and a significant positive correlation with T4 (r = 0.317, P = 0.010). No significant correlations were observed between vitD and reproductive hormones, including estradiol, LH, or FSH. Conclusion: Serum vitD levels are significantly lower in Iranian girls with ICPP compared to healthy controls. These findings suggest that vitD may influence pubertal development; therefore, routine assessment of vitD status in girls presenting with precocious puberty may be clinically warranted, particularly in populations with a high background prevalence of deficiency. https://abi.tums.ac.ir/index.php/abi/article/view/201 https://abi.tums.ac.ir/index.php/abi/article/download/201/143