Effects and Underlying Mechanism of Vitamin D Combined With rhGH and GnRH-a Therapy on the Growth and Development of Girls With Central Precocious Puberty

<b>Aims/Background</b> Vitamin D plays a crucial role in regulating puberty development. Furthermore, it is closely associated with the onset and progression of precocious puberty. Therefore, this study aimed to investigate the effects of vitamin D supplementation on growth and development in girls with central precocious puberty (CPP) undergoing recombinant human growth hormone (rhGH) combined with gonadotropin-releasing hormone analogues (GnRH-a) therapy and to analyze its underlying mechanisms. <b>Methods</b> This retrospective study analyzed the clinical data from 100 CPP girls who received rhGH combined with GnRH-a in Jinhua Maternal and Child Health Care Hospital between June 2020 and December 2022. Study participants were divided into the vitamin D supplementation group (VitD group, <i>n</i> = 43) and the non-supplementation group (non-VitD group, <i>n</i> = 57) according to whether vitamin D was supplemented during treatment. Growth and development indicators, including bone age/chronological age (BA/CA), predicted adult height (PAH), Tanner stage, sex hormone levels, and bone mineral density (BMD) of the left heel were compared between the two groups before treatment and 12 months after treatment. <b>Results</b> After 12 months of treatment, the VitD group demonstrated a significantly reduced BA/CA ratio compared to the non-VitD group (<i>p</i> = 0.002). The VitD group had a significantly higher PAH than the non-VitD group (<i>p</i> = 0.009). Furthermore, the comparison of the Tanner stage between the two groups showed a statistically significant difference (<i>p</i> = 0.033). Additionally, the estradiol (E₂), GnRH excitation test-follicle stimulating hormone (FSH) peak value and GnRH excitation test-luteinizing hormone (LH) peak value were significantly lower in the VitD group than in the non-VitD group (<i>p</i> < 0.001, <i>p</i> = 0.014, <i>p</i> < 0.001). Moreover, the BMD of the left heel in the VitD group significantly increased to that of the non-VitD group following 12 months of treatment (<i>p</i> = 0.005). <b>Conclusion</b> Supplementation of vitamin D during rhGH combined with GnRH-a treatment further enhances the growth and development of CPP girls. This positive impact may be due to its crucial role in inhibiting the growth of breast epithelial cells, reducing sex hormone levels, and reducing treatment-induced BMD.