Serum Osteocalcin Levels in Girls with Central Precocious Puberty: Relation to the Onset of Puberty

Osteocalcin is the non-collagenous protein produced by osteoblasts in bone. When it is released into systemic circulation in its uncarboxylated form, it regulates fat and glucose metabolism. Recent studies have shown that osteocalcin is also involved in male fertility. Because the onset of puberty is determined by ethnic, genetic, environmental, and metabolic factors, we focused on determining the role of osteocalcin in the onset of puberty. Central precocious puberty (CPP) is defined as the activation of the hypothalamic pituitary-gonadal axis before the age of 8 in girls and 9 in boys. CPP is diagnosed when peak luteinizing hormone (LH) reaches >= 5.0 IU/I after stimulation with gonadotropin-releasing hormone (GnRH). This retrospective study included 206 girls who showed breast budding before the age of 8 and whose bone age was more advanced than their chronological age. The CPP group included 100 girls who were diagnosed with CPP, and 106 girls were the non-CPP group whose peak LH did not reach >= 5.0 IU/I after GnRH stimulation test. Serum osteocalcin levels were measured to investigate the relationship between osteocalcin and the onset of puberty. Our data showed that serum osteocalcin levels were significantly higher in the CPP group (87.7 +/- 24.4 ng/ml vs. 68.3 +/- 19.5 ng/ml, P < 0.001). The multivariate analysis revealed that an increase in bone age and peak LH was significantly associated with the serum osteocalcin level. The results of this study suggest that serum osteocalcin is associated with the onset of puberty in girls.