Serum phoenixin levels in girls with central precocious puberty and premature thelarche.

Background And Aim: Phoenixin (PNX), a newly discovered neuropeptide associated with reproduction, has been speculated to be involved in precocious puberty. Therefore, we assessed serum PNX levels in girls with precocious puberty.

Methods: Serum phoenixin-14 (PNX-14) and phoenixin-20 (PNX-20) levels were determined in girls with central precocious puberty (CPP) and premature thelarche (PT) and in healthy controls (n = 58 per group). Spearman's correlation was used to analyze the correlations between variables. Receiver operating characteristic curves were used to evaluate the performance of PNX for the diagnosis of CPP. Significant predictors of serum PNX levels were determined using least absolute shrinkage and selection operator regression and multiple linear regression analyses.

Results: Serum PNX-14 and PNX-20 levels were significantly higher in girls with CPP than in the controls; however, no significant differences in serum PNX-14 and PNX-20 levels were observed between girls with PT and the controls. PNX-20 levels were positively correlated with basal luteinizing hormone (LH) levels, peak LH levels, the peak LH to follicle-stimulating hormone (FSH) ratio, and estradiol levels. No significant correlation was observed between PNX-14 levels and any of these parameters. Multivariate linear regression analysis revealed that PNX-20 levels exhibited the strongest correlation with peak LH/FSH values. The areas under the curve (AUCs) of PNX-14 and PNX-20 for predicting CPP were 0.628 (cut-off value, 100.12 pg/mL; sensitivity, 44.6%; specificity, 77.6%) and 0.775 (cut-off value, 360.03 pg/mL; sensitivity, 66.5%; specificity, 79.3%), respectively. When these two indicators were combined, the AUC was 0.785.

Conclusions: Serum PNX levels may be associated with precocious puberty in girls and can be used as an auxiliary CPP indicator. However, given the low sensitivity and specificity of PNX, it should not be used as a single diagnostic indicator of CPP.