Insulin-like Growth Factor-Binding Protein 3 (IGFBP-3)
Fasting Required: No

Specimen: Blood

Results: 3-5 Business Days

Description:
The main reason doctors order the IGFBP-3 test is for its usefulness as an indicator of whether someone is producing a normal amount of human growth hormone. In this way, the IGFBP-3 test is used to check for pituitary gland disorders and abnormalities in growth hormone production.

Advantages of IGFBP-3 over IGF-1 are the higher levels in young children which gives a better insight between normal and subnormal levels. The IGFBP-3 assay is also used to diagnose children with short stature having normal GH levels. Some children with short stature give subnormal IGF-I levels despite normal GH levels. IGFBP-3 was found to be a more reliable parameter for monitoring the usefulness of therapy. Therefore, it is a useful aide to the measurement of IGF-I.

Methodology
Immunoassay (IA)

Clinical Significance
Insulin-like growth factor binding proteins bind IGF-I and IGF-II with high affinity but do not bind insulin. Of the six distinct IGF binding proteins structurally characterized at this time, IGFBP-3 has been shown to be the major carrier of the IGFs, transporting approximately 95% of circulating IGF-I and IGF-II.
IGFBP-3 is growth hormone (GH) responsive. Thus, levels are high in cromegaly and low in hypopituitarism, and levels increase in GH-deficient children after GH administration. Thus, both assays and the ratios of IGF-I/IGFBP-2 and IGFBP-2/IGFBP-3 are useful as markers of GH action and for discriminating between growth hormone deficiency and short stature due to other etiologies in children. Other causes of short stature that result in reduced IGFBP-3 levels include poorly controlled diabetes.
The IGFBP-3 assay is useful in assessing nutritional status, since IGFBP-3 decreases during both caloric and protein restriction.

Note: Result turn around times are an estimate and are not guaranteed. Our reference lab may need additional time due to weather, holidays, confirmation/repeat testing, or equipment maintenance.