Specimen Information

Type

Gold, SST

Volume

0.5 ml

Transport Info

Centrifuge and immediately transfer serum to separate plastic tube
Frozen

Fasting Required?

False

Clinical Significance

Insulin-like growth factors (IGF-1 and IGF-2) are peptides with structural homology to insulin. They exhibit growth-promoting effects as well as insulin-like activity through autocrine, paracrine, and endocrine actions. The serum concentrations of IGFs are regulated by two influences: Growth hormone (GH) in a feedback relationship. Nutritional status. Circulating IGF-1 is almost totally protein bound to high-affinity binding proteins called IGF binding proteins (IGFBPs). Six IGFBPs have been identified. IGFBP-3 is the major carrier of IGFs in serum and is present in the highest concentrations. More than 90% of IGF-1 and IGF-2 is bound to IGFBP-3 and the complex in humans has a half life of 12-15 hours. IGFBP-3 may provide a storage pool for IGF-1 and may be involved in the transport of IGF-1 to tissues. Serum concentrations of IGFBP-3 are fairly constant throughout the day and are controlled by GH and IGF-1 levels. The measurement of IGFBP-3 is useful in the evaluation of several clinical situations: Short stature in children, Acromegaly, Nutritional status. In the assessment of short stature in children, the secretion of GH fluctuates throughout the day and the half life is only 15-20 minutes, making a single random measurement of GH difficult to interpret. IGFBP-3 exhibits much less diurnal variation and can provide more reliable and useful information. IGFBP-3 levels are less age-dependent and are higher in young children than IGF-1 levels. This allows for better differentiation between normal and subnormal levels. IGFBP-3 levels show a better correlation with GH sufficiency than single measurements of IGF-1 or IGF-2. IGFBP-3 measurements can also be useful for monitoring the efficacy of treatment for GH deficiency. A combination of both IGFBP-3 and IGF-1 measurements can provide improved information concerning the evaluation of short stature in children. For patients with acromegaly, serum IGFBP-3 levels have been shown to be useful in diagnosis and may serve as a marker of GH excess. In addition, IGFBP-3 measurement may be useful in assessing surgical cure of somatotroph tumors. IGFBP-3 measurements can also be useful in the evaluation of nutritional status. The levels of IGFBP-3 decline during fasting and chronic malnutrition as do IGF-1 levels. Measurement of both proteins can aid in assessing nutritional status and in monitoring the response to therapy.