| Precocious puberty is characterized by conditions wherein secondary sexual developments occur in girls aged less than eight years and boys aged less than nine years.80% cases are diagnosed as central precocious puberty. Central precocious puberty (CPP) refers to premature activation of the hypothalamic-pituitary-gonadal (HPG) axis, and accompany with growth acceleration, advancement of bone age, and elevated sex steroid levels for age. Vary from CPP, incompletely precocious puberty(IPP) is defined as isolated development of breasts or pubic hair without advanced bone maturation. As the variant type of central precocious puberty, with incompletely activation of HPG axis, IPP may not have lasting adverse effects and does not require treatment. It is found that IPP is not always a self-limited condition and may sometimes progress to CPP. Therefore, The differential diagnosis and treatment are required for IPP and CPP in clinical evaluation. GnRH stimulation test is the golden standard for distinguishing central precocious puberty from incompletely precocious puberty. But the repeatedly venous punctures for blood sample collection may induce a great deal of pain for both children and parents. With development of chemiluminescence immunoassay, the Sensitivity for LH and FSH detection are significantly improved and it can provide effective discrimination between pre- and early adolescence. But the basal values of LH and FSH can not provide reliable results and auxiliary methods are needed. Ultrasound techniques are becoming increasingly important in evaluation of reproduction system, offering both a mean of diagnosis and a useful therapeutic tool. And it is a real-time examination for the visualisation of ovarian and uterine pathologies. It can work as assisted technique for CPP and IPP dignosis.IGF-1 is the tertiary hormone in the somatotropic axis that plays key roles in somatic growth. The growth axis, like all neuro-endocrine systems, functions through hypothalamic, pituitary, and target organ interactions. In recent years, IGF-I has been considered one of the components contributing to early signaling processes controlling LHRH secretion and the timing of female puberty. IGF-1 has been demonstrated to affect GnRH neuronal function in several ways, kisspetins are products of the KiSS-1 metastasis suppressor gene and ligands of the G protein-coupled receptor 54 (GPR54) and play a key role in the timing of puberty. It is found that IGF-I is an upstream regulator of the KiSS-1 gene at the time of female puberty and play critical regulatory roles in maintaining healthy female reproductive cyclicity, but the underlying mechanism is still unknown. PI3K are classically activated via growth factor receptors (RTKs). Active RTKs elicit authophosphorylation of the receptor and binding of SH2 domain expressing proteins to the phosphorylated tyrosine residues in the receptor. IGF-1 receptor can favor the activation of PI3K/AKT and regulate HPG axis function. We speculate that PI3K/AKT may get involved in the stimulating effects of IGF-1 on KISS1/GRP45.In our research, the difference of ultrasonic results, hormone levels between CPP and IPP group were analyzed, the IGF-1 levels were evaluated and the correlation between IGF-1 and other diagnosis results were discussed. Neonatal rat hypothalamic neurons were isolated and cultured for the investigation on the stimulating mechanism of IGF-1.PurposeTo study the differences of ultrasonic results, hormone levels between CPP and IPP group, to investigate the promotion effects of IGF-1 on KISS1/GRP45 expression and discuss the underlying mechanism, to analyze the correlation between IGF-1 and other diagnostic results.Methods1) Girls with premature sexual development were admitted to the Clinical Center of the Shandong university protocol. We obtained informed consent from the parents and the children themselves. The girls were classified into two groups.40 girls were selected for the CPP group, the average age is 7.75±2.43 years old and the range of diagnostic age is 1～11 years old. In IPP group,40 girls were involved and the average age is 7.50±1.64 years old. Detail medical history and evaluation results of physical and serum examination were collected.2) Analyze the differences of ultrasonic results, hormone levels between CPP and IPP group.3) Neonatal SD rat hypothalamic neurons were isolated and cultured with 10 ng/ml or 100 ng/ml IGF-1 for 2h,4h,6h and 24h. GnRH contents in cultured medium were evaluated by radioimmunoassay. KISS1, GPR54 and GnRH mRNA expression were analyzed by Quantitative Real-time PCR. Western-blot method was used to evaluate the influence of IGF-1 on AKT and p-AKT expression in hypothalamic neurons.4) Investigate the correlation between IGF-1 and ultrasonic examination&hormone levels.Results1. Differential analysis of clinical diagnosis results between CPP and IPP group.1) The bone age in CPP group was 9.19±2.73 years and the age range is 2～12 years. The bone age was significantly higher compared with the chronological age in CPP group. The bone age in IPP group was 8.08±1.97 years and the range is 1.5～9 years, there is no significantly difference between bone age and chronological age in IPP group. Bone age was more advanced in the CPP group than the IPP group. Similar result was also observed in BA/CA ratio in these two groups.2) Most of the uterine and ovarian measurements were significantly different between the girls with CPP and IPP. For the uterus, differences were noted in volumes. For the ovaries, differences were found in the number of ovarian follicles and size of largest follicle.3) Serum level of LH, FSH, E2 and T were significantly higher in CPP group, and PRL, PRG contents were not different in these two groups.4) IGF-1 level in CPP and IPP were 318.94±155.81 ng/ml and 191.46±107.89 ng/ml, respectively. IGF-1 content was more advanced in CPP group than the IPP group.2. IGF-1 promotes KISS1/GRP45 expression via PI3K/AKT pathwayTreatment of cultured Neonatal rat hypothalamic neurons with 10 ng/ml or 100 ng/ml IGF-1 resulted in a time-dependent increase in GnRH release. After 4 hours treatment, GnRH conents increased to the peak level and subsequently declined in both IGF-1 groups. KISS1, GPR54 and GnRH mRNA expression were significantly increased in IGF-1 group treated for 4 hours. p-AKT expression were also up regulated after treated with IGF-1. LY294002 could inhibit the promotion effects of IGF-1 on AKT phosphorylation and induce the down regulation of KISS1/GPR54 mRNA expression.3. Correlation analysis of IGF-1 and clinical diagnosis between two groups.1) Significant correlation was found between serum IGF-1 level and BA/CA ratios in both CPP and IPP group.2) Significant correlation of IGF-1 content with uterus volume, ovary volume, the number of ovarian follicles were found in CPP group. There is no significant correlation between IGF-1 content and uterus volume, ovary volume and the number of ovarian follicles in IPP group.3) Significant correlation of IGF-1 content with LH, E2 and T was observed in CPP group.Conclusion1) Bone age, ultrasonic examination and hormone evaluation can work as auxiliary methods for the differential diagnoses of CPP and IPP.2) IGF-1 promotes KISS1/GRP45 expression via PI3K/AKT pathway.3) The correlation between IGF-1 and hormone, IGF-1 and ultrasonic index were found, and IGF-1 was involved in the initiation of puberty. |
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