A Study of PEG-somatropin in the Treatment of Children With Idiopathic Short Stature

Inclusion Criteria: * Boys are between 4 and 9 years of age and girls are between 4 and 8 years of age. * Height \<-2 SD for chronological age. * Growth velocity\<5.0 cm/yr. * GH peak concentration ≥10.0 ng/mL in two different stimulation tests. * The difference of bone age (BA) and chronological age (CA) is within -2 to +2. * IGF-1 concentration is between -2 SDS to +2 SDS. * Prepubertal Status(Tanner Stage I). * Birth weight within the normal range. * Growth hormone treatment-naive. * Subjects are willing and able to cooperate to complete scheduled visits, treatment plans and laboratory tests and other procedures, to sign informed consent. Exclusion Criteria: * Subjects with abnormal liver and kidney functions (ALT \> upper limit of normal value; Cr \> upper limit of normal value). * Subjects are positive for anti-HBc, HbsAg or HbeAg in Hepatitis B virus tests. * Subjects with known highly allergic constitution or allergy to investigational product or its excipient. * Subjects with systemic chronic disease and immune deficiency. * Patients diagnosed with tumor. * Patients with mental disease. * Patients with other types of abnormal growth and development. 1. Growth hormone deficiency (GHD) (confirmed by GH stimulation test); 2. Turner syndrome (confirmed by karyotype test of girls); 3. Noonan syndrome (hypertelorism, pectus carinatum, hypophrenia, frequently with skin disease and congenital heart disease, missense mutation of the protein tyrosine phosphatase, non-receptor type 11 (PTPN11) gene on chromosome 12 for half of the patients, for both male and female patients); 4. Laron sydrome (confirmed by IGF-1 generation test); 5. Small for gestational age ( the birth height or weight is below the tenth percentile or 2 SD, with catch-up growth uncompleted at 2 years old). * Growth disorders caused by malnutrition or hypothyroidism (thyroid function test). * Congenital skeletal abnormalities or scoliosis, claudication. * Subjects with impaired glucose regulation (IGR) (including impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT) ) or diabetes). * Subjects with abnormal electrolyte, blood gas analysis (vein), creatine kinase. * Subjects who took part in other clinical trials within 3 months. * Subjects who received medications which may interfere GH secretion or GH function, or other hormones within 3 months (such as sex steroids, glucocorticoids, etc.). * For patients with potential high tumor risks such as tumor markers exceed normal range and some other relative information, they may be excluded from the treatment. * Other conditions which is inappropriate for this study in the opinion of the investigator.