Inclusion Criteria:

• One of the following diagnoses and candidacy for SAIZEN® therapy:

A)GHD: documented pre-established diagnosis of GHD with a GH peak response of <10 μg/L with 2 GH stimulation tests, without priming with oestradiol. B)Turner syndrome: documented pre-established diagnosis by karyotype.

• Prepubertal status according to Tanner Pre-established history of normal thyroid function or adequate substitution for at least 3 months.
• Weight for stature within the population specific normal range (>5th and <95th percentiles) for gender Willingness and ability to comply with the protocol for the duration of the study.
• Parent's or guardian's written informed consent, given before any study related procedure that is not part of the subject's normal medical care, with the understanding that the subject or parent/guardian may withdraw consent at any time without prejudice to future medical care. If the child is old enough to read and write, a separate assent form will be given.

Exclusion Criteria:

• Acquired GHD due to central nervous system tumour, trauma, infection, infiltration (documented by imaging), and history of irradiation or cranial surgery
• Previous treatment with GH, GHRH, anabolic steroids or any treatment affecting growth.
• Previous treatment with corticosteroids, except in case of topical or inhaled corticosteroid administration for atopic disease. Corticosteroids for hormonal substitution are also allowed if the condition and the treatment regimen have been stable for at least 3 months.
• Severe associated pathology affecting growth such as malnutrition, malabsorption, or bone dysplasia.
• Chronic severe kidney disease.
• Chronic severe liver disease.
• Chronic infectious disease.
• Acute or severe illness during the previous 6 months.
• Significant concomitant illness that would interfere with participation or assessment in this study.
• Active malignancy (except non-melanomatous skin malignancies that have undergone surgical excision and/or biopsy, diagnosis and treatment to resolution)
• History or active Idiopathic intra-cranial hypertension (benign intracranial hypertension or pseudo-tumor cerebri).
• Diabetes Mellitus type I & II.
• Any autoimmune disease.
• Previous screening failure in this study.
• Use of an investigational drug or participation in another clinical study within the last three months.