Clinical Study of Pegylated Somatropin (PEG Somatropin) to Treat SGA Children With Short Stature

Inclusion Criteria: * The patients are diagnosed as being clinically full term small for gestational age infant. * Girl are 3-6 years old, boys are 3-7 years old. * Be in preadolescence (Tanner stage 1). * The child did not achieve catch-up growth when he/she entered the group (the definition of catch-up growth is that the height is higher the third percentile with the same age and gender) (Appendix 2 and 3). * The height of child is shorter than -2SDS of the median of normal children with the same age and gender when he/she entered the group (the mean height and height standard deviation of normal children with the same age and gender of normal children regard the height data in the physical development investigation data of children aged 0-18 in 9 cities of China (2005) as standard \[13\], Appendix 4 and 5). * Within a year before entering the group, after any growth hormone stimulation test, the peak concentration of growth hormone in serum\>10 µg/L. * Bone age≤ the actual age+1. * The function of glucose regulation is normal: fasting blood glucose \< 5.6mmol/L. * Birth gestational age ≥ 37 weeks. * The subjects and their guardians sign the informed consent (if the subjects is lack of ability for signing the informed consent, his legal guardian can write the subjects name instead). * All experimental drug groups completed the main phase (52 weeks) of Phase II clinical trials, and the participants with complete follow-up records can enter the extension phase, provided that the continuous cessation of the use of pegylated recombinant human growth hormone injection lasts ≤ 8 weeks after the end of the first phase treatment and before the start of the extended study. * Only when the subjects and their guardians are fully informed, express their willingness, and are able to cooperate in completing the treatment, follow-up, and various tests of the extension phase study, and have signed a written informed consent form, can they enter the extension phase trial. Exclusion Criteria: * People with abnormal liver or kidney function (ALT\> 2 times the upper limit of normal value, Cr\> the upper limit of normal value). * Patients are positive for hepatitis B core antigen (HBc), hepatitis B surface antigen (HBsAg) or hepatitis B e antigen (HBeAg). * People with known highly allergic constitution or allergy to the drug or the excipient of the study. * People with diabetes, severe cardiopulmonary, hematological system and malignant tumors diseases or general infection, immune deficiency and patients with mental disease. * Other abnormal growth and development, such as Turner syndrome, Laron syndrome, growth hormone receptor deficiency. * Potential tumor patients (family history). * Patients who used growth hormone for treatment. * Subjects took part in other clinical trial study within 3 months. * Patients used other hormonal for treatment within 3 months (such as sex hormone, glucocorticoid and etc., treat for more than a month) and received the drug treatment which may interfere with the secretion of GH or GH function (oxandrolone, growth hormone releasing hormone and etc.); * Other conditions which in the opinion of the investigator preclude enrollment into the study. * Subjects who have used the following medications within 2 months prior to entering the expansion phase of the trial: * 1\) Aromatase inhibitors (including but not limited to letrozole, anastrozole) used continuously for 1 month; * 2\) Gonadotropin-releasing hormone analogs (including but not limited to triptorelin, leuprolide, goserelin) used continuously for 1 month; * 3\) Sex hormones (including but not limited to any type of estrogen, progestin, and androgen) used continuously for 1 month; * 4\) Anabolic steroids (including but not limited to oxymetholone, danazol, stanozolol) used continuously for ≥ 1 month; * 5\) Oral or intravenous corticosteroids used for 1 month.