Osteocalcin: A potential marker to identify and monitor girls with rapidly progressive central precocious puberty.

Aim: To evaluate the suitability of serum osteocalcin (OC) as a marker to distinguish between rapidly and non-rapidly progressive central precocious puberty (RP-CPP and NRP-CPP), as well as its potential to assess growth rates following treatment with gonadotropin-releasing hormone agonist (GnRHa).

Methods: Serum levels of OC were measured using enzyme-linked immunosorbent assays in girls diagnosed with either RP-CPP or NRP-CPP as well as in normal control subjects. Receiver operating characteristic (ROC) curve analysis was performed to determine the cut-off value for OC. Multivariate linear regression analysis was used to analyse the main influencing factors associated with OC.

Results: Serum OC levels were higher in the CPP girls when compared to normal controls (110.76 ± 43.69 vs 55.97 ± 20.96 ng/mL, P < 0.001). The level in the RP-CPP group was higher than the NRP-CPP group (153.28 ± 33.89 vs 88.33 ± 29.26 ng/mL, P < 0.001). The cut-off value of OC levels for distinguishing between RP-CPP and NRP-CPP was 107.05 ng/mL, the sensitivity was 94.7% and the specificity was 77.8%, which was superior to using the basal luteinising hormone (B-LH) levels, and the area under ROC curve (AUC) were 0.933 versus 0.695, respectively. Following 1-2 years of treatment with GnRHa for girls with CPP, both OC levels and the growth rates decreased to pre-pubertal values. B-LH levels, bone age and body weight were also significant factors, which affected OC levels.

Conclusions: Serum OC levels may be a useful marker for distinguishing RP-CPP from NRP-CPP. In addition, it was also found to be a useful predictor for growth rate during GnRHa treatment.