Inclusion Criteria:

Subjects must meet all of the following inclusion criteria to be eligible for enrollment into the trial:

• Prepubertal caucasian boys between 4 and 10 years of age and girls between 4 and 9 years of age.
• Girls: Tanner stage 1 breast development
• Boys: Testis volume < 3 ml
• Tanner stage 1 public hair development (to exclude confounding effect of adrenarche on growth velocity, insulin sensitivity and body composition).
• (In case of any signs or symptoms of gonadal puberty a GnRH-Test must decide if the subject is still pubertal.)
• Height < -2 SD for chronological age (Brandt/Reinken).
• Growth velocity SDS below 0 SD for chronological age (Brandt/Reinken based on 12+ 3 months observation period before screening).
• Premature born defined as < 1500 g birth weight.
• GH sufficiency (GH level > 7 ug/l following any routine GH stimulation test).
• Written informed consent of both parents (legal guardians) and oral/written consent of subject due to age specific information.

Exclusion Criteria:

Subjects presenting with any of the following will not be included in the trial:

• Other endocrine diseases except for well substituted hypothyroidism.
• Severe chronic diseases or medication that might influence linear growth or insulin sensitivity (e.g. Glucocorticoids).
• Positive GAD and IA-2 antibodies (for type 1 diabetes).
• History of malignancy
• Children who meet all of the following criteria:
• actual body height < -2,5 SDS (Brandt/Reinken) and parent adjusted target height < -1 SDS (Hermanussen and Cole, 2003)
• length and/or body weight retardations adjusted to gestational age at birth < -2,0 SDS (Lawrence et al., 1989, Voigt et al., 1996)
• children with chronological age > 4 years and
• growth velocity < 0 SDS during the last year before inclusion.
• Chromosomal aberrations or syndromes.
• Suspected non-compliance or impossibility to follow the two or three year treatment schedule, respectively (e.g. social implications).
• Severe hemiparesis and severe CNS defects
• Retinopathia > third degree or laser treatment as newborns.
• Participation in any other clinical trial during active treatment phase.
• Other severe acute or chronic medical or psychiatric condition or clinically relevant laboratory abnormality that may increase the risk associated with trial participation or investigational product administration or may interfere with the interpretation of trial results and, in the judgement of the investigator, would make the subject inappropriate for entry into this trial.