This project is designed to answer the question: Is there an acute IGFBP-3 response in normal children?

Our specific hypothesis states that under the influence of growth hormone secretagogues, intact IGFBP-3 molecule will undergo proteolysis and liberate IGFBP-3 fragments, along with other components of the ternary complex. This proteolysis will result in measurable rise in IGFBP-3, which will indicate the subject's growth hormone status. Short children with growth hormone deficiency will not show an IGFBP-3 response.

The diagnosis of growth hormone deficiency is problematic, given the shortcoming of the standard growth hormone stimulation test. This study is designed to investigate a new tool for the diagnosis of growth hormone deficiency.

Ten short, prepubertal children, who fulfill the inclusion criteria, will undergo a two-secretagogue standard growth hormone stimulation test, and an insulin like growth factor binding protein-3 (IGFBP-3) stimulation test simultaneously. During this test, components of the ternary complex moieties, viz, insulin-like growth factor-I (IGF-I), IGFBP-3 and acid labile subunit (ALS) will also be measured along with growth hormone.

The aim of this study is to detect an acute rise in IGFBP-3 of >15% from baseline.

The importance of this study is that it inculcates the specificity and improved sensitivity of stimulated IGFBP-3 in the diagnosis of growth hormone deficiency.

Inclusion Criteria:

• Bone age < 10 years female, < 12 years male
• Pubertal status: Girls: Tanner I for breast development. Boys: testicular volume of ≤ 3 cc, as measured by the standardized orchidometer (Prader type). The onset of pubic hair development up to and including Tanner III is allowed in the study.
• Adequate nutrition: body mass index ≥ 25th percentile for gender.

Exclusion Criteria:

• Syndromic short stature
• Chronic illnesses.
• Other disorders, including osteo- or chondrodystrophies, and endocrine causes of short stature such as Cushing syndrome, and untreated hypothyroidism.