Transferrin levels

Under normal circumstances, transferrin is one-fourth to one-third saturated with iron. The level of saturation may decrease in systemic infection or cancer and in iron deficiency anemia, the most common nutritional deficiency in the United States. In individuals with iron deficiency anemia, transferrin levels are increased. The level of saturation with iron increases in iron overload syndromes such as hereditary hemochromatosis or as a result of repeated blood transfusions, as is the case in thalassemia patients. Determinations of total plasma iron (TI) and plasma total iron binding capacity (TIBC) are routinely performed in the clinical biochemistry laboratory. The TIBC value reflects transferrin levels in plasma the amount of iron that can be bound by transferrin is equal to TIBC x 0.7. Total plasma iron levels in iron deficiency anemia become abnormal before hemoglobin levels show any change. 

Transferrin levels increase in iron deficiency anemia. Ferritin levels decrease. Transferrin binds Fe3+ to its amino acid side-chains, while ferritin binds Fe3+ as ferric hydroxide micelles. 

Both forms of PEM are associated with hy-percortisolemia.The level of cortisol in kwashiorkor is lower, however, than in marasmus, likely due to decreased adrenocortical function caused by low protein intake (and not adrenal failure). If a sufficiently high level of cortisol is not maintained, then adequate muscle protein is not mobilized to sustain hepatic protein synthesis. Indeed, hypoproteinemia, evident by the decreased serum albumin and transferrin levels, is more acute in kwashiorkor than marasmus. 

Unlike marasmic or well-nourished children, those with kwashiorkor have low transferrin levels and detectable free iron in the plasma (Sive et al., 1996). Uncomplexed iron is extremely toxic due to its ability to generate free radicals by the Haber-Weiss and Fenton reactions.The onslaught of opportunistic infections in the malnourished also elicits production of free radicals and accentuates the oxidative stress. 

He Y, Lee T, Leong SK (1999) Time course of dopaminergic cell death and changes in iron, ferritin and transferrin levels in the rat substantia nigra after 6- hydroxydopamine (6-OHDA) lesioning. Free Radic Res 31 103-112. 

E606 Dasgupta, A. and Hussain, S. (1990). Elevated lipid peroxidation products and depleted transferrin levels in the serum of patients with chronic renal failure. Qin. Chem. 36, 962, Abstr. 52. 

A. Fleming MF, Anton RF, Spies CD. A review of genetic, biological, pharmacological, and clinical factors that affect carbohydrate-deficient transferrin levels. Alcohol Clin Exp Res 2004 28 1347-55,... 

Jejunal juice. IgG-globulin is readily digested so that samples require immediate inhibition of proteases (1 drop of 10% EACA and Trasylol) if IgG is to be assessed. IgM seems less readily digested and secretory IgA is unaffected. It is too early to fully evaluate jejunal juice estimations, but it can be said that excessive content of IgM is nearly always found in untreated celiac disease (D7). High immunoglobulin, albumin, and transferrin levels are easily demonstrated in protein-losing states (offer a simple alternative to I-PVP), and with samples taken at different levels can delineate the area affected. Since juice can be sampled at the same time as biopsies, I believe jejunal juice estimations will have a useful future. 

Plasma transferrin levels are commonly measured in the evaluation of disorders of iron metabolism (see below). It is customary to measure transferrin concentration... 

Hypotransferrinemiacan result from protein malnutrition and accompanies hypoalbuminemia. Since transferrin has a much shorter half-life (8 days) than albumin (19 days), measurement of the transferrin level may be a more sensitive indicator of protein malnutrition than albumin measurement (see also chapter 17). Hypotransfer-rinemia also results from excessive renal loss of plasma proteins (e.g., in nephrotic syndrome). 

Van Cott K, Lubon H, Gwazdauskas F, et al. Recombinant human protein C expression in the milk of transgenic pigs and the effect on endogenous milk immunoglobulin and transferrin levels. Transgenic Res., 2001 10(1) 43-51. 

Transferrin levels total iron-binding capacity (TTBC) (normal = 300 micrograms/dl)... 

Transferrin is one of the proteins responsible for binding and transporting both iron and manganese throughout the body. One study (Vahlquist et al. 1975) reported no correlation between infant cord blood and maternal blood transferrin levels. The same study reported an increase in plasma transferrin from 1.68-H/-0.60 mg/mL in blood from infants at 6 weeks of age, to a peak of 2.60+1-0.21 mg/mL at 10 months, with values stabilizing at these adult levels throughout 16 years of age. The authors did not comment as to the statistical difference, if any, of these values. 

The liver synthesizes a number of serum proteins and releases them into the blood. These proteins decrease in the blood during protein malnutrition. Two of these serum proteins, albumin and transferrin (an iron-binding transport protein), are often measured to assess the state of protein malnutrition. Serum albumin is the traditional standard of protein malnutrition. Neither measurement is specific for protein malnutrition. Serum albumin and transferrin levels decrease with hepatic disease, certain renal diseases, surgery, and a number of other conditions, in addition to protein malnutrition. Serum transferrin levels also decrease in iron deficiency. Percy Veere s values were below the normal range for both of these proteins, indicating that his muscle mass is unable to supply sufficient amino acids to sustain both synthesis of serum proteins by the liver and gluconeogenesis. 

Percy Veere has several indicators of his protein malnntrition his serum albumin and transferrin levels are below normal, his mid-npper-arm mnscle circumference (MUAMC) is at the 12th percentile, and his creatinine-height index (CHI) was at 85%. The low levels of semm proteins reflect a low dietary protein intake, and possibly diminished capacity to absorb dietary amino acids. Consequently, amino acids are being mobilized from degradation of protein in mnscle and other tissues to supply precursors for new protein synthesis as well as glnconeogenesis. The result is a loss of muscle mass, indicated by the MUAMC and the CHI, and decreased levels of serum proteins. 

Serum ferritin levels are depressed and bone marrow storage iron is vanishingly small or nonexistent in iron deficiency. The serum transferrin levels, usually derived from the iron-binding capacity, are elevated, while the iron levels are low (less than 50 p.g/dL), and serum transferrin saturation is less than 16%. Microscopic examination of a blood smear reveals microcytic and hypochromic erythrocytes, and the hematocrit and hemoglobin levels are depressed [28,29]. 

Elevations of serum iron occur in various other pathological conditions hemolytic anemia, lead toxicity, pyridoxine deficiency, pernicious anemia, acute liver necrosis, and iron poisoning. Serum transferrin levels usually decrease in these cases and the percent saturation increases in response to increased iron in the extracellular fluid. Desferrioxamine, a siderophote from actinomycetes, has been used to treat patients with acute iron toxicity (30,31]. The toxicity of iron was reviewed in a previous volume of this series [6]. 

The role of transferrin has been investigated by measuring iron absorption by isolated intestinal loops. Although it appears that transferrin accelerates iron absorption, the rate of intestinal absorption of iron is not limited by transferrin levels in blood. A number of hormones influence iron absorption by the intestine. The molecular mechanism of these hormonal effects is not known, and only the ultimate response to the hormonal stimulus can be described. In many if not all cases, the hormonal effect on iron absorption is probably secondary to the action of the hormone on other physiological or biochemical functions. Pituitary and thyroid hormones stimulate iron absorption thyroid hormones probably act by increasing erythropoiesis and oxygen consumption. 

Gilbert, L., Dean, R. E., and Karaganis, A., 1979, Iron dextran administration via TPN solution in malnourished patients with low serum transferrin levels, J. Parent. Enter. Nutr. 3 509. 

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