Insulin-Like Growth Factor–Binding Protein-3 (IGFBP-3)

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Subject: Insulin-Like Growth Factor–Binding Protein-3 (IGFBP-3)

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Definition

  • This 264-amino-acid peptide (molecular weight, 29 kDa) is produced by the liver. It is the most abundant of a group of IGFBPs that transport and control bioavailability and half-life of insulin-like growth factors (IGFs), in particular IGF-I. In addition to its IGF-binding function, IGFBP-3 also exhibits intrinsic growth-regulating effects that are not yet fully understood but have evoked interest with regard to a possible role of IGFBP-3 as a prognostic tumor marker. Other name: somatomedin C–binding protein.

  • Normal range: see Table 16.49.

 
TABLE 16–49
Normal Ranges for IGFBP-3

Use

  • Diagnosing growth disorders

  • Diagnosing adult growth hormone deficiency

  • Monitoring of recombinant human growth hormone treatment

  • Possible adjunct to IGF-I and growth hormone in the diagnosis and follow-up of acromegaly and gigantism

Interpretation

Increased In

  • Overproduction of GH

  • Excessive rhGH therapy

  • Chronic renal failure

Decreased In

  • GH deficiency

  • GH resistance

  • Fasting/chronic malnutrition

  • Hepatic failure

  • Diabetes mellitus

Limitations

  • IGF-I and IGFBP-3 reference ranges are highly age dependent, and results must always be interpreted within the context of the patient's age.

  • Discrepant IGFBP-3 and IGF-I results can sometimes occur due to liver and kidney diseases; however, this is uncommon, and such results should alert laboratories and physicians to the possible occurrence of a preanalytic or analytic error.

  • At this time, IGFBP-3 cannot be reliably used as a prognostic marker in breast, colon, prostate, or lung cancer.

  • IGFBP-3 assays exhibit significant variability among platforms and manufacturers. Direct comparison of results obtained by different assays is problematic. Rebaselining of patients is preferred if assays are changed.

 
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