Test Directory

The insulin-like growth factor (IGF) system plays a critical role in the growth and differentiation of normal and malignant cells. The components of the IGF system include growth hormone (GH), IGF-I and II, type I and II receptors, IGF binding proteins and proteases. IGF binding proteins were first identified for their high affinity interactions with IGF-I and IGF-II.

IGFBP-3 is the most abundant IGFBP species in circulation and binds 75% to 90% of circulating IGF-I in a ternary complex consisting of IGFBP-3, IGF-I and acid-labile subunit (ALS). IGFBP-3 modulates the activity of IGF-1 and to increase their half lives. It has been postulated that IGFBP-3 is regulated by GH and originates in the liver as low levels were observed in patients with impaired hepatic function.

IGFBP-3 has historically been used in the investigation of growth hormone deficiency, acromegaly, hypopituitarism and to monitor recombinant GH therapy. IGFBP-3 is known to modulate the actions of IGFs in circulation as and at the IGF-1 receptor. IGFBP-3 has also been shown to exhibit distinct biological effects independent of the IGF/IGF-1 receptor axis. Recent studies have impaired interaction of IGFBP-3 with a variety of proteins or signaling cascades critical to cell cycle control and apoptosis; however, the actual mechanism of IGFBP-3 action is unclear.

Specimen Type: Serum

Collection Container: Gold Top, Serum Separator

Alternate Collection Container: Red Top, Plain

Desired Specimen Volume: 1 mL

1. Collect a gold top, serum separator tube via venipuncture.

1. Separate serum from cells.
2. Transfer 1 mL of serum to a clear aliquot tube (screw cap).

This test may exhibit interference when sample is collected from a person who is consuming a supplement with a high dose of biotin (also termed as vitamin B7 or B8, vitamin H, or coenzyme R). It is recommended to ask all patients who may be indicated for this test about biotin supplementation. Patients should be cautioned to stop biotin consumption at least 72 hours prior to the collection of a sample.

Transport to the laboratory refrigerated. 

See patient report.

Several factors influence IGFBP-3 levels, including age, sexual development, nutrition, and hepatic and renal function. IGFBP-3 increases during early childhood and puberty and then decreases slightly in adult life. Levels of this binding protein decrease during fasting and chronic malnutrition. IGFBP-3 levels are decreased in hepatic failure and diabetes mellitus, but are increased in chronic renal failure.