Gordon D. McLaren

Iron absorption and metabolism.

Purpose of review Intestinal iron absorption is an essential physiological process that is regulated by the liver-derived peptide hepcidin. This review will describe recent advances in hepcidin biology and enterocyte iron transport. Recent findings Hepcidin acts as a repressor of iron absorption and its expression in turn reflects a range of systemic cues, including iron status, hypoxia, erythropoiesis and inflammation. These act through proteins on the hepatocyte plasma membrane such as HFE, hemojuvelin and transferrin receptor 2 to alter transcription of the hepcidin gene. Bone morphogenetic protein-SMAD signaling provides a key pathway of hepcidin activation, whereas the membrane-bound serine protease matriptase-2 and the erythroid factor growth differentiation factor 15 have emerged as important negative regulators of hepcidin expression. At the enterocyte itself, the recent demonstration of a chaperone for delivering iron to ferritin and new data on iron release from the hepcidin target ferroportin are helping to define the pathway of iron movement across the intestinal epithelium. Summary Disturbances in the hepcidin regulatory pathway underlie a range of iron metabolism disorders, from iron deficiency to iron loading, and there is considerable promise that the exciting recent advances in understanding hepcidin action will be translated into improved diagnostic and therapeutic modalities in the near future.

Hemochromatosis and Iron Overload Screening (HEIRS) study design for an evaluation of 100,000 primary care-based adults.

BackgroundThe HEIRS Study will evaluate the prevalence, genetic and environmental determinants, and potential clinical, personal, and societal impact of hemochromatosis and iron overload in a multiethnic, primary care-based sample of 100,000 adults over a 5-year period. Participants are recruited from 5 Field Centers. Laboratory testing and data management and analysis are performed in a Central Laboratory and Coordinating Center, respectively. MethodsParticipants undergo testing for serum iron measures and common mutations of the hemochromatosis gene (HFE) on chromosome 6p and answer questions on demographics, health, and genetic testing attitudes. Participants with elevated values of transferrin saturation and serum ferritin and/or C282Y homozygosity are invited to undergo a comprehensive clinical examination (CCE), as are frequency-matched control subjects. These examinations provide data on personal and family medical history, lifestyle characteristics, physical examination, genetic counseling, and assessment of ethical, legal, and social implications. Primary and secondary causes of iron overload will be distinguished by clinical criteria. Iron overload will be confirmed by quantification of iron stores. Recruiting family members of cases will permit DNA analysis for additional genetic factors that affect iron overload. ResultsOf the first 50,520 screened, 51% are white, 24% are African American, 11% are Asian, 11% are Hispanic, and 3% are of other, mixed, or unidentified race; 63% are female and 37% are male. ConclusionsInformation from the HEIRS Study will inform policy regarding the feasibility, optimal approach, and potential individual and public health benefits and risks of primary care-based screening for iron overload and hemochromatosis.

Delayed hepcidin response explains the lag period in iron absorption following a stimulus to increase erythropoiesis

Introduction: The delay of several days between an erythropoietic stimulus and the subsequent increase in intestinal iron absorption is commonly believed to represent the time required for body signals to programme the immature crypt enterocytes and for these cells to migrate to the villus. Recent data however suggest that signals from the body to alter absorption are mediated by circulating hepcidin and that this peptide exerts its effect on mature villus enterocytes. Methods: We have examined the delay in the absorptive response following stimulated erythropoiesis using phenylhydrazine induced haemolysis and correlated this with expression of hepcidin in the liver and iron transporters in the duodenum. Results: There was a delay of four days following haemolysis before a significant increase in iron absorption was observed. Hepatic hepcidin expression did not decrease until day 3, reaching almost undetectable levels by days 4 and 5. This coincided with the increase in duodenal expression of divalent metal transporter 1, duodenal cytochrome b, and Ireg1. Conclusion: These results suggest that the delayed increase in iron absorption following stimulated erythropoiesis is attributable to a lag in the hepcidin response rather than crypt programming, and are consistent with a direct effect of the hepcidin pathway on mature villus enterocytes.

Physician Alerts to Prevent Symptomatic Venous Thromboembolism in Hospitalized Patients

Background— Venous thromboembolism (VTE) prophylaxis remains underused among hospitalized patients. We designed and carried out a large, multicenter, randomized controlled trial to test the hypothesis that an alert from a hospital staff member to the attending physician will reduce the rate of symptomatic VTE among high-risk patients not receiving prophylaxis. Methods and Results— We enrolled patients using a validated point score system to detect hospitalized patients at high risk for symptomatic VTE who were not receiving prophylaxis. We randomized 2493 patients (82% on Medical Services) from 25 study sites to the intervention group (n=1238), in which the responsible physician was alerted by another hospital staff member, or the control group (n=1255), in which no alert was issued. The primary end point was symptomatic, objectively confirmed VTE within 90 days. Patients whose physicians were alerted were more than twice as likely to receive VTE prophylaxis as control subjects (46.0% versus 20.6%; P<0.0001). The symptomatic VTE rate was lower in the intervention group (2.7% versus 3.4%; hazard ratio, 0.79; 95% CI, 0.50 to 1.25), but the difference did not achieve statistical significance. The rate of major bleeding at 30 days in the alert group was similar to that in the control group (2.1% versus 2.3%; P=0.68). Conclusions— A strategy of direct notification of the physician by a staff member increases prophylaxis use and leads to a reduction in the rate of symptomatic VTE in hospitalized patients. However, VTE prophylaxis continues to be underused even after physician notification, especially among Medical Service patients.

A phase 1/2, dose-escalation trial of deferasirox for the treatment of iron overload in HFE-related hereditary hemochromatosis.

Hereditary hemochromatosis (HH) is characterized by increased intestinal iron absorption that may result in iron overload. Although phlebotomy is widely practiced, it is poorly tolerated or contraindicated in patients with anemias, severe heart disease, or poor venous access, and compliance can vary. The once‐daily, oral iron chelator, deferasirox (Exjade) may provide an alternative treatment option. Patients with HH carrying the HFE gene who were homozygous for the Cys282Tyr mutation, serum ferritin levels of 300‐2000 ng/mL, transferrin saturation ≥45%, and no known history of cirrhosis were enrolled in this dose‐escalation study to characterize the safety and efficacy of deferasirox, comprising a core and an extension phase (each 24 weeks). Forty‐nine patients were enrolled and received starting deferasirox doses of 5 (n = 11), 10 (n = 15), or 15 (n = 23) mg/kg/day. Adverse events were generally dose‐dependent, the most common being diarrhea, headache, and nausea (n = 18, n = 10, and n = 8 in the core and n = 1, n = 1, and n = 0 in the extension, respectively). More patients in the 15 mg/kg/day than in the 5 or 10 mg/kg/day cohorts experienced increases in alanine aminotransferase and serum creatinine levels during the 48‐week treatment period; six patients had alanine aminotransferase >3× baseline and greater than the upper limit of normal range, and eight patients had serum creatinine >33% above baseline and greater than upper limit of normal on two consecutive occasions. After receiving deferasirox for 48 weeks, median serum ferritin levels decreased by 63.5%, 74.8%, and 74.1% in the 5, 10, and 15 mg/kg/day cohorts, respectively. In all cohorts, median serum ferritin decreased to <250 ng/mL. Conclusion: Deferasirox doses of 5, 10, and 15 mg/kg/day can reduce iron burden in patients with HH. Based on the safety and efficacy results, starting deferasirox at 10 mg/kg/day appears to be most appropriate for further study in this patient population. (HEPATOLOGY 2010)

Screening for Hemochromatosis in Primary Care Settings

Hemochromatosis is an inherited disease, characterized by excessive absorption of dietary iron, that can lead to progressive iron accumulation in tissues and organ damage [1]. It has been proposed as a candidate for routine screening with measurement of transferrin saturation [1-20]. To evaluate screening as a primary care strategy, four programs in the United States integrated iron status screening, with an emphasis on hemochromatosis, into their routine health care services for adults. In March 1997, at a meeting at the Centers for Disease Control and Prevention, the directors of these four programs described the major challenges that they faced and the lessons that they learned in implementing their programs. Seven issues were consistently reported to need resolution in the implementation of hemochromatosis screening: 1) changes in case definitions of hemochromatosis from the classic description, 2) selection of screening threshold values and identification of false-positive cases, 3) variability and lack of standardization of screening test measurements, 4) physician education, 5) informed consent and concerns about medical and genetic discrimination, 6) patient compliance with screening and therapy, and 7) incidental detection of iron deficiency. The four programs described here are in different stages of operation and in different settings (Table 1). They are at Rochester General Hospital at the University of Rochester, Rochester, New York; the Kaiser Permanente Medical Care Program, San Diego, California; the Veterans Affairs Medical Center, Fargo, North Dakota; and St. Johns Health System, Springfield, Missouri. Table 1. Description and Results of Four Screening Programs for Hemochromatosis in the United States in 1997* Changes in Case Definitions of Hemochromatosis The definition of hemochromatosis has traditionally been based on late clinical and pathologic findings of iron overload [1], and the diagnosis has typically been made by excluding other conditions (such as secondary iron overload or primary liver disease) and finding characteristic pathologic evidence on liver biopsy [21]. Recently, as a result of increased emphasis on early diagnosis and population-based screening, it has been proposed that the definition of hemochromatosis be changed [1, 21, 22]. The difficulties raised by exploring new case definitions in the four hemochromatosis screening programs discussed here are threefold. First, comparisons between program findings and previous research must be made by using reported prevalences based on similar criteria (the presence or absence of iron overload and clinical symptoms). Second, the penetrance of hemochromatosis is not 100%; thus, genetic tests and even biochemical criteria for the early diagnosis of hemochromatosis are new and are not yet fully correlated with clinical outcomes [1, 21]. Third, participating physicians may be unfamiliar with these new criteria; moreover, the existing literature may contradict screening protocols and confuse patient care. Selection of Screening Threshold Values and False-Positive Cases When these screening programs were being planned, transferrin saturation threshold values were chosen to establish a screening threshold that would be sensitive enough to identify most cases of hemochromatosis without producing too many false-positive results [18-20]. Recommended threshold values range from 45% to 70% [6-16]. However, the underlying demographic characteristics of the population being screened may influence the transferrin saturation threshold and the prevalence of hemochromatosis [23-26]. For example, a lower cut-point has been suggested for women because it has been shown that at a relatively high transferrin saturation, such as 62% or more, 40% of putative female homozygotes do not screen positive for hemochromatosis even though almost 100% of male homozygotes do [12, 20]. In addition, studies suggest that threshold values should be lower for black persons than for white persons [23, 24]. These lower cut-points have not been directly tested for their association with the newly described genetic HFE mutations or clinical outcomes [27-29]. Because of the low prevalence of hemochromatosis in the population (at most, 8 per 1000 among white persons in the United States), the positive predictive value of the initial random transferrin saturation test for hemochromatosis is also low. In this case, it is only 0.08, with a sensitivity of 0.96 and a specificity of 0.94. In the four screening programs, the transferrin saturation was elevated on initial testing in 2.5% to 5.8% of the several populations screened (Table 2). A repeated test, done while the patient is fasting, with a threshold equal to or higher than that used for the initial test (Table 1) markedly improves the tests positive predictive value [4]. In most patients, hemochromatosis was excluded because the result of the second test was normal. However, 30% of patients who had an elevated transferrin saturation on a repeated test were found to have a primary liver disorder or secondary iron overload. The underlying prevalence of these conditions in a population affects the number of false-positive results for hemochromatosis. In some instances, hemochromatosis coexists and acts synergistically with these other conditions, resulting in a more complicated clinical picture and possibly an altered treatment plan. Table 2. Proportion of Hemochromatosis Screening Test Results That Were Positive in Four Programs in the United States in 1997* Variability and Lack of Standardization of the Transferrin Saturation Screening Test Serum transferrin saturation is considered a sensitive and specific marker for hemochromatosis [5, 16], but biological and analytic variability complicate its use. The variation may be greater than physicians are accustomed to, and the proper interpretation of such high within-subject variation must be explained. For example, the results of initial and repeated transferrin saturation tests may vary by as much as 50% in the same person (that is, the second value may be 50% lower than the first). Biological (individual) variability requires that the second test be done while the patient is fasting, and the patient has to have taken no vitamins or iron supplements for 24 hours. Even with these dietary restrictions, however, transferrin saturation can still vary considerably in the same person. Each program described here used only a single laboratory to perform transferrin saturation testing; thus, variations were not due to interlaboratory differences. The persistent variation that the Kaiser Permanente program experienced despite standardized blood sampling conditions led them to investigate the cause of the variation. By sending split specimens to an outside laboratory and comparing the results with in-house results, they documented that the variation was due to biological and not analytic causes. Lack of laboratory standards and proficiency testing for transferrin saturation testing may also cause variability of test results and may affect the proportion of positive results (Table 2). Laboratory proficiency in testing transferrin saturation and its total iron-binding capacity component are not routinely monitored by any national agency. Many methods and instruments are available for measuring transferrin saturation, but which ones are most reliable or valid is not known [30]. Individual physicians can send serum specimens to laboratories that have been evaluated by the College of American Pathologists or the Centers for Disease Control and Prevention and can encourage participating laboratories to be evaluated by these agencies before initiating iron status screening. Physician Education and Involvement Early diagnosis and management of hemochromatosis are possible only when physicians are knowledgeable about the techniques involved. Many physicians, however, are not well versed in these areas or in basic genetics [31-33]. Little information is available on newer case definitions of hemochromatosis and the management of young or asymptomatic patients. In all of the screening programs discussed here, participating primary care physicians were initially unconvinced that hemochromatosis existed in their patient population. Many physicians were unfamiliar with the transferrin saturation test, and this resulted in the ordering of inappropriate tests instead. Resistance to diagnostic algorithms is common, particularly when they differ from protocols learned during medical training. All of the screening programs reported that a one-time continuing medical education session for participating physicians was inadequate preparation for screening: Physicians require in-depth, ongoing education about hemochromatosis screening and management. To address this need, Kaiser Permanente created videotapes showing clinical manifestations and patient concerns; St. Johns Health System mailed educational packets on diagnosis and management to physicians when a patients initial test result was positive. This mailing was followed by a telephone call or a personal visit from the primary investigator. All programs reported that physician involvement in hemochromatosis screening and in education programs increased as cases were detected. The screening and diagnostic algorithms for hemochromatosis and the record keeping required to track laboratory and therapeutic phlebotomy are complicated, and it is difficult to standardize patient care among primary care physicians and specialists. To address these problems, the Kaiser Permanente program adopted a centralized approach to hemochromatosis screening and management that relied on two primary care physicians and on selected referral physicians who were familiar with the protocols. Most physicians wanted assistance not only with the logistics of screening but also with the process of giving information on screening and disease to their patients. In addition, pa

Genome-Wide Association Study Identifies Genetic Loci Associated with Iron Deficiency

The existence of multiple inherited disorders of iron metabolism in man, rodents and other vertebrates suggests genetic contributions to iron deficiency. To identify new genomic locations associated with iron deficiency, a genome-wide association study (GWAS) was performed using DNA collected from white men aged ≥25 y and women ≥50 y in the Hemochromatosis and Iron Overload Screening (HEIRS) Study with serum ferritin (SF) ≤ 12 µg/L (cases) and iron replete controls (SF>100 µg/L in men, SF>50 µg/L in women). Regression analysis was used to examine the association between case-control status (336 cases, 343 controls) and quantitative serum iron measures and 331,060 single nucleotide polymorphism (SNP) genotypes, with replication analyses performed in a sample of 71 cases and 161 controls from a population of white male and female veterans screened at a US Veterans Affairs (VA) medical center. Five SNPs identified in the GWAS met genome-wide statistical significance for association with at least one iron measure, rs2698530 on chr. 2p14; rs3811647 on chr. 3q22, a known SNP in the transferrin (TF) gene region; rs1800562 on chr. 6p22, the C282Y mutation in the HFE gene; rs7787204 on chr. 7p21; and rs987710 on chr. 22q11 (GWAS observed P<1.51×10−7 for all). An association between total iron binding capacity and SNP rs3811647 in the TF gene (GWAS observed P = 7.0×10−9, corrected P = 0.012) was replicated within the VA samples (observed P = 0.012). Associations with the C282Y mutation in the HFE gene also were replicated. The joint analysis of the HEIRS and VA samples revealed strong associations between rs2698530 on chr. 2p14 and iron status outcomes. These results confirm a previously-described TF polymorphism and implicate one potential new locus as a target for gene identification.

Clinical manifestations of hemochromatosis in HFE C282Y homozygotes identified by screening

BACKGROUND Patients with hemochromatosis may suffer organ damage from iron overload, often with serious clinical consequences. OBJECTIVE To assess prevalences of self-reported symptoms and clinical signs and conditions in persons homozygous for the hemochromatosis gene (HFE) mutation (C282Y) identified by screening. METHODS Participants were adults 25 years of age or older enrolled in the Hemochromatosis and Iron Overload Screening (HEIRS) Study. C282Y homozygotes (n=282) were compared with control participants without the HFE C282Y or H63D alleles (ie, wild type/wild type; n=364). RESULTS Previously diagnosed C282Y homozygotes and newly diagnosed homozygotes with elevated serum ferritin levels had higher prevalences of certain symptoms such as chronic fatigue (OR 2.8; 95% CI 1.34 to 5.95, and OR 2.0; 95% CI 1.07 to 3.75, respectively), and had more hyperpigmentation on physical examination (OR 4.7; 95% CI 1.50 to 15.06, and OR 3.7; 95% CI 1.10 to 12.16, respectively) and swelling or tenderness of the second and third metacarpophalangeal joints (OR 4.2; 95% CI 1.37 to 13.03, and OR 3.3; 95% CI 1.17 to 9.49, respectively) than control subjects. Joint stiffness was also more common among newly diagnosed C282Y homozygotes with elevated serum ferritin than among control subjects (OR 2.7; 95% CI 1.38 to 5.30). However, the sex- and age-adjusted prevalences of self-reported symptoms and signs of liver disease, heart disease, diabetes and most other major clinical manifestations of hemochromatosis were similar in C282Y homozygotes and control subjects. CONCLUSIONS Some symptoms and conditions associated with hemochromatosis were more prevalent among C282Y homozygotes identified by screening than among control subjects, but prevalences of most outcomes were similar in C282Y homozygotes and controls in this primary care-based study.

Arthritis of hemochromatosis: Clinical spectrum, relation to histocompatibility antigens, and effectiveness of early phlebotomy☆

Five patients who presented with arthritis as the sole manifestation of hereditary hemochromatosis and 51 family members were studied. Studies included clinical evaluation for the presence of arthritis and hemochromatosis, roentgenography of hands, knees, and pelvis, serum iron and serum ferritin measurements, complete HLA typing for 50 of the A and B loci, and, when indicated, liver biopsy. Arthritis occurred in 45 percent of persons with hemochromatosis. Although typical involvement of second and third metacarpophalangeal joints was observed in all five patients and some family members, two with typical arthritis did not have characteristic radiographic changes, two had constitutional symptoms without arthropathy, and one had unilateral hand changes. A specific HLA haplotype (A2/B17 in Family 1 and A29/B15 in Family 2) correlated with hereditary hemochromatosis but not with the arthropathy. Phlebotomy alleviated the early constitutional symptoms but did not help advanced arthritis. Anti-inflammatory drugs, intraarticular injections of glucocorticoids, and resection osteotomies of metacarpal heads were other treatment modalities.

Transient Pure Red-Cell Aplasia: Cell-Mediated Suppression of Erythropoiesis Associated with Hepatitis

Transient pure red-cell aplasia is a rare complication of persistent acute hepatitis. We have investigated possible mechanisms for marrow suppression in one such patient who developed erythroid aplasia in the course of transfusion-related hepatitis. The patients lymphocytes, obtained during the acute illness, markedly inhibited erythroid colony formation by donor marrow. After the patient recovered, remission lymphocytes in co-culture did not inhibit colony formation. No reversible suppression was demonstrable by addition of patient serum. These observations suggest that hematocytopenias associated with hepatitis may result from cell-mediated suppression induced by hepatic injury.