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Assessment of iron status.

OBJECTIVE: To review the clinical assessment of iron deficiency and excess. CONCLUSIONS: Two key iron-related proteins in the human body are ferritin which is the iron storage protein, and the transferrin receptor, which controls the entry of iron-bearing transferrin to cells. Intact ferritin and truncated transferrin-receptor molecules are present in serum in direct quantitative proportion to their total tissue content. Ferritin and transferrin-receptor production are precisely and reciprocally regulated at a posttranscriptional level. This is achieved by an iron-responsive element-binding protein that interacts with iron-responsive elements in the mRNA of each, but with contrary effects. Increases in serum ferritin reflect increased storage iron and increases in serum transferrin receptor reflect cellular iron deficits. The combined use of these two measurements allows accurate definition of the entire range of body iron status. This is valid even in situations where assessment of iron status has been notoriously problematic, including periods of rapid growth, in pregnancy, in conditions associated with inflammation, and in trained athletes.

Female↗

Usefulness and limitations of laboratory and hepatic imaging studies in iron-storage disease.

Liver biopsy with measurement of hepatic iron concentration is the most certain procedure for evaluation of iron-storage disease, although use of computed tomography and magnetic resonance imaging procedures recently have been proposed as alternative, noninvasive methods for estimating the degree of iron overload. The results of these imaging procedures were compared with those of other noninvasive techniques and liver biopsies in 48 patients. Final diagnoses, based on synthesis of clinical and laboratory data, included (a) primary hemochromatosis (n = 25; 19 homozygous, 6 heterozygous); (b) secondary hemochromatosis (n = 7); (c) alcoholic liver disease (n = 11); (d) chronic active hepatitis (n = 3); and (e) other (n = 2). Serum ferritin and computed tomography or magnetic resonance scanning had 100% sensitivity in detecting hepatic iron overload more than fivefold above the upper limit of normal (greater than 10.7 mumol Fe/100 mg dry liver) but did not detect lesser degrees of iron overload reliably, including those found in 6 of 13 patients with untreated homozygous primary hemochromatosis and 3 of 7 with secondary hemochromatosis. Computed tomography and magnetic resonance imaging were more specific than ferritin (64% and 92% vs. 21%) in the detection of iron excess, more than five times the upper limit of normal. Among magnetic resonance imaging measures, the ratio of the second echo signal intensities of liver to paraspinous muscle was the most sensitive and most specific for detection of this degree of iron overload. The degree of correlation between hepatic iron concentration and results of noninvasive laboratory or imaging studies were insufficient to permit prediction of hepatic iron content by noninvasive studies alone. It is concluded that computed tomography or magnetic resonance scanning as currently usually used is not cost-effective in routine evaluation of iron overload, although these imaging procedures may play a role in patients in whom liver biopsy is contraindicated. Because of their low cost and ready availability, serum ferritin and transferrin saturation tests remain the preferred screening studies for iron overload. Liver biopsy with quantitative iron measurement remains the study of choice for the definitive diagnosis of hemochromatosis.

Biopsy↗

Chronic dietary iron overload in rats results in impaired calcium sequestration by hepatic mitochondria and microsomes [corrected].

The purpose of these experiments was to determine whether chronic dietary iron overload causes impairment of hepatic mitochondrial and/or microsomal calcium sequestration. Experimental iron overload was produced by feeding three groups of rats a chow diet supplemented with 3.0% (wt/wt) carbonyl iron for up to 8 weeks achieving graded increases in hepatic iron concentrations ranging from 1360 to 3170 micrograms/g. At low levels of iron overload, there were no changes in mitochondrial oxidative metabolism or calcium sequestration, whereas at moderate and high degrees of iron loading, both of these parameters were significantly reduced. In contrast, there were significant decreases in microsomal cytochrome P450 levels and microsomal calcium sequestration at all three levels of iron loading. These abnormalities occurred at hepatic iron concentrations at which the authors have previously found evidence of hepatic organelle lipid peroxidation. These alterations in organelle calcium sequestration may impair intracellular calcium homeostasis in the liver and contribute to subsequent cellular injury.

Animals↗

Antioxidant activity of silybin in vivo during long-term iron overload in rats.

BACKGROUND & AIMS: Hepatic iron toxicity may be mediated by free radical species and lipid peroxidation of biological membranes. The antioxidant property of silybin, a main constituent of natural flavonoids, was investigated in vivo during experimental iron overload. METHODS: Rats were fed a 2.5% carbonyl-iron diet and 100 mg.kg body wt-1.day-1 silybin for 4 months and were assayed for accumulation of hepatic lipid peroxidation by-products by immunocytochemistry, mitochondrial energy-dependent functions, and mitochondrial malondialdehyde content. RESULTS: Iron overload caused a dramatic accumulation of malondialdehyde-protein adducts into iron-filled periportal hepatocytes that was decreased appreciably by silybin treatment. The same beneficial effect of silybin was found on the iron-induced accumulation of malondialdehyde in mitochondria. As to the liver functional efficiency, mitochondrial energy wasting and tissue adenosine triphosphate depletion induced by iron overload were successfully counteracted by silybin. CONCLUSIONS: Oral administration of silybin protects against iron-induced hepatic toxicity in vivo. This effect seems to be caused by the prominent antioxidant activity of this compound.

Adenosine Triphosphate↗

Endometrial glandular haemosiderosis in homozygous beta-thalassaemia.

Female patients with beta-thalassaemia major usually suffer from hypogonadotropic hypogonadism associated with amenorrhea, anovulation and infertility, attributed to the deposition of haemosiderin in the pituitary gland as well as in the ovaries. Pregnancies are rare and, with few exceptions, occur mainly in patients with beta-thalassaemia intermedia. Our study presents histopathological evidence that deposition of haemosiderin occurs in the endometrial glandular epithelium of 3 patients with beta-thalassaemia major. This deposition is mainly evident in the apical part of these cells above the nuclei, and should be taken into consideration as a contributing factor to the infertility in these patients by altering endometrial receptivity for implantation. In 2 patients who received effective iron chelating treatment with desferrioxamine the endometrial haemosiderin deposits either disappeared (patient C.R.), or were significantly reduced (patient G.L.).

Adult↗