Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1024 page)

   Monitoring effectiveness of nutritional repletion; a more sensitive indicator than prealbumin, transferrin index, or retinol-binding protein

   Interpretation

Increased In

   Acromegaly and gigantism

   Pregnancy (2–3 times nonpregnant values)

Decreased In

   Pituitary deficiency

   Laron dwarfism

   Anorexia or malnutrition

   Acute illness

   Hepatic failure

   Hypothyroidism

   DM

   Normal aging

INSULIN-LIKE GROWTH FACTOR-II

   Definition

   IGF-II is a 7.5 kDa, 67-amino-acid peptide that is thought to mediate some of the actions of growth hormone (GH). IGF-II peptide is structurally homologous to IGF-I and proinsulin. IGF-II is secreted by the liver and other tissue and is postulated to have mitogenic and metabolic actions at or near the sites of synthesis. IGF-II also appears in the peripheral circulation, where it circulates primarily in a high molecular weight tertiary complex with IGF-binding protein-3 (IGFBP-3) and acid-labile subunit. The proportion of unbound IGF-II in the circulation has been estimated at >5%. Plasma levels of IGF-II are dependent on adequate levels of GH and other factors, including adequate nutrition. The actions of IGF-II are mediated by binding to specific cell surface receptors. Although its specific physiologic role has not been defined, it has been postulated that the interplay of IGF-I and IGF-II with the different cell surface receptors and circulating binding proteins modulates tissue growth.