Clinical Briefs: Hereditary Hemochromatosis and Diabetes; HRT and Dry Eye Syndrome; Myeloperoxidase and Coronary Artery Disease
December 15, 2001 3 minutes read
Prevalence of Hereditary Hemochromatosis in Late-Onset Type 1 Diabetes Mellitus
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It comes as a surprise to many clinicians that hemochromatosis (HCRM) is literally one of the most common genetic disorders in persons of northern European descent; in America, it has a gene frequency of 10%, hence it is more frequent than such disorders as cystic fibrosis. HCRM can manifest diversely, including liver disease, diabetes, heart failure, arthritis, and pituitary hypogonadism. Ellervik and colleagues postulated that HCRM is often overlooked as an etiology of, or contributor to, such disorders.
The study population included 716 type 1 adult-onset diabetics. Adult diabetics were chosen because systemic manifestations of HCRM usually manifest after age 50. The odds ratio (4.6) for homozygous HCRM in the diabetic population when compared to the unselected comparison population suggests a relevant role for HCRM in adult onset type 1 diabetes.
All patients who were HCRM homozygotes manifested an elevated serum transferrin saturation. Ellervik et al conclude that HCRM, a potentially correctable cause of diabetes and other maladies, is often overlooked. Their data suggest that, extrapolating from their Danish population, 15-20 cases of type 1 diabetes per million population could be prevented by discovery and appropriate treatment of HCRM with simple venesection. They further suggest that any type 1 adult onset diabetic merits screening for HCRM, since disease progress could be favorably affected by venesection control of HCRM.
Ellervik C, et al. Lancet. 2001;358: 1405-1409.
Hormone Replacement Therapy and Dry Eye Syndrome
Dry eye syndrome (DES), also known as keratoconjunctivitis sicca, can cause substantial debilitation due to adverse symptoms of dryness and irritation, as well as the morbidity of increased risk of corneal infection, ultimately potentially leading to permanent visual impairment. Unfortunately, management tools for DES are often unsatisfactory.
The combination of estrogen and progesterone to menopausal women, hormone replacement therapy (HRT), is used by more than one third of American women, but the relationship between HRT and DES is not yet studied. Schaumberg and colleagues used the data set of the participants in the Women’s Health Study (n = 39,876) to evaluate the relationship between HRT, estrogen replacement therapy (ERT), or non-use of hormone replacement with DES.
HRT use was significantly associated with DES. Estrogen replacement therapy (ERT) was associated with the highest prevalence of DES (9.1%), compared with HRT users (6.7%) and never-users of HRT (5.9%).
The mechanism(s) by which gonadal steroids might influence ocular lubrication is uncertain. Basic science studies have suggested that androgens favorably effect lacrimal and meibomian gland function, but estrogen may exacerbate dry eye. Schaumberg et al suggest that clinicians inform potential recipients of HRT/ERT that an increased likelihood of DES may be associated with its use.
Schaumberg DA, et al. JAMA. 2001; 286:2114-2119.
Association Between Myeloperoxidase Levels and Risk of Coronary Artery Disease
The association between inflammatory markers and the presence of atherosclerosis suggests that C-reactive protein, adhesion molecules, and other cytokines are potentially etiologically involved. Moreover, there is some substantiation for the use of such markers to predict risk of acute vascular events.
Myeloperoxidase (MPO) is an enzyme that is secreted from a variety of cells, such as neutrophils and macrophages. Normally, MPO is stored within quiescent cells, but is not released until the cells are activated, as occurs in states of acute inflammation. There is a putative link between MPO and endothelial dysfunction. Zhang and colleagues sought to establish the relationship between MPO activity and coronary artery disease. Study subjects included 333 adults, approximately half of whom had angiographically-demonstrated CAD.
MPO levels were significantly higher in persons with CAD than controls. Comparing levels of MPO, those in the highest quartile of MPO had almost a 9-fold increased odds ratio of CAD, compared with those in the lowest quartile. Zhang et al suggest that MPO levels may serve as a marker to identify persons with CAD who are not otherwise detected by typical risk factors.
Zhang R, et al. JAMA. 2001;286: 2136-2142.
Dr. Kuritzky, Clinical Assistant Professor, University of Florida, Gainesville, is Associate Editor of Internal Medicine Alert.
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