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

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 " пїЅbinding protein.
  • Normal range: see Table 16.49.

пїЅ пїЅ

TABLE 16 " пїЅ49Normal Ranges for IGFBP-3View LargeTABLE 16 " пїЅ49Normal Ranges for IGFBP-3 Age (in years Unless Otherwise Specified) Reference Range (mg/mL) 0 " пїЅ15 d 0.5 " пїЅ1.4 1 0.7 " пїЅ3.6 2 0.8 " пїЅ3.9 3 0.9 " пїЅ4.3 4 1.0 " пїЅ4.7 5 1.1 " пїЅ5.2 6 1.3 " пїЅ5.6 7 1.4 " пїЅ6.1 8 1.6 " пїЅ6.5 9 1.8 " пїЅ7.1 10 2.1 " пїЅ7.7 11 2.4 " пїЅ8.4 12 2.7 " пїЅ8.9 13 3.1 " пїЅ9.5 14 3.3 " пїЅ10 15 3.5 " пїЅ10 16 3.4 " пїЅ9.5 17 3.2 " пїЅ8.7 18 3.1 " пїЅ7.9 19 2.9 " пїЅ7.3 20 2.9 " пїЅ7.2 21 " пїЅ25 3.4 " пїЅ7.8 26 " пїЅ30 3.5 " пїЅ7.6 31 " пїЅ35 3.5 " пїЅ7.0 36 " пїЅ40 3.4 " пїЅ6.7 41 " пїЅ45 3.3 " пїЅ6.6 46 " пїЅ50 3.3 " пїЅ6.7 51 " пїЅ55 3.4 " пїЅ6.8 56 " пїЅ60 3.4 " пїЅ6.9 61 " пїЅ65 3.2 " пїЅ6.6 66 " пїЅ70 3.0 " пїЅ6.2 71 " пїЅ75 2.8 " пїЅ5.7 76 " пїЅ80 2.5 " пїЅ5.1 81 " пїЅ85 2.2 " пїЅ4.5

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 patients 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.