Keshan Disease: A Severe Cardiomyopathy
Keshan disease is the most prominent ailment associated with a severe deficiency of selenium (SE). This congestive cardiomyopathy, named after a county in China where it was first documented, primarily affects children and women of reproductive age in specific geographic areas with SE-poor soil. While SE deficiency is a necessary condition for the disease to occur, it is often triggered or exacerbated by additional factors, such as infection with the Coxsackievirus.
The cardiac damage seen in Keshan disease is severe and includes multifocal necrosis and fibrosis of the heart muscle. In areas where the disease is endemic, a combination of dietary SE supplementation and monitoring has proven effective in reducing its incidence and mortality rates significantly.
The Role of Selenoproteins and Oxidative Stress
The core of selenium's importance lies in its role in producing selenoproteins, which are essential for many bodily functions. A key family of these proteins is the glutathione peroxidases (GPXs), which act as powerful antioxidants. In individuals with Keshan disease, SE deficiency leads to low levels of these protective enzymes, leaving the heart vulnerable to oxidative damage from free radicals. This damage can be particularly acute in the mitochondria of heart muscle cells, where energy production generates reactive oxygen species.
Kashin-Beck Disease: An Endemic Osteoarthritis
Another significant disease linked to SE deficiency, in combination with other nutritional factors like iodine deficiency, is Kashin-Beck disease. This chronic, degenerative osteoarthropathy affects cartilage and joints, leading to deformities, restricted movement, and stunted growth in children and adolescents.
Kashin-Beck disease is prevalent in specific regions with SE-deficient soil, particularly parts of China, Siberia, and North Korea. While the exact mechanisms are complex and multifactorial, the connection to SE deficiency is well-documented. For children living in these areas, SE supplementation can help reduce the incidence and clinical symptoms of the disease.
Other Health Complications Associated with Low SE
Beyond these two specific endemic diseases, SE deficiency contributes to a broader range of health problems. The mineral's impact on various systems highlights its widespread importance.
Thyroid Function
The thyroid gland has the highest concentration of SE in the body, primarily because it is needed for the enzymes (iodothyronine deiodinases) that convert inactive thyroid hormone (T4) into its active form (T3). A deficiency can impair this conversion process, leading to symptoms of hypothyroidism such as fatigue and weight gain. SE deficiency can also exacerbate conditions like autoimmune thyroiditis.
Immune System Impairment
Selenium is critical for a healthy immune system. It modulates immune and inflammatory responses, with deficiency compromising the body's ability to fight off infections. Studies have shown that low SE status can leave the body more vulnerable to certain viruses, and it is also linked to a faster progression of HIV to AIDS in affected individuals.
Reproductive Issues
Infertility in both men and women has been associated with low selenium levels. It is vital for male reproductive health, including sperm development and motility. The concentration of SE in testicular tissue is significant, underscoring its role in fertility.
Comparison of Selenium Deficiency Disorders
| Feature | Keshan Disease | Kashin-Beck Disease | General SE Deficiency |
|---|---|---|---|
| Primary Manifestation | Congestive cardiomyopathy, heart failure, and cardiomegaly. | Degenerative osteoarthropathy with joint and cartilage deformities. | Wide range of non-specific symptoms, including fatigue, weakness, and thyroid issues. |
| Affected Population | Primarily children and women of childbearing age in endemic regions. | Children and adolescents in endemic regions. | General population with inadequate intake, or those with malabsorption. |
| Key Contributing Factors | Severe SE deficiency plus viral infection (e.g., Coxsackievirus). | SE deficiency combined with other nutritional deficits like iodine. | Inadequate dietary intake due to location, poor absorption, or surgical procedures. |
| Treatment | SE supplementation, often with other cardiac therapies. | SE supplementation to reduce clinical symptoms. | Dietary changes and supplementation, often under medical supervision. |
Diagnosing and Treating SE Deficiency
Identifying a selenium deficiency often requires evaluating a person's diet, geographic location, and medical history. Blood or hair analysis can help measure selenium levels, with some biomarkers like selenoprotein P being more reliable for long-term status.
For treatment, dietary adjustments are key. Foods rich in selenium include Brazil nuts, seafood, meat, and whole grains. In cases of diagnosed deficiency, medical supervision is recommended for supplementation, as there is a narrow therapeutic window before toxicity can occur.
Conclusion: The Importance of a Balanced Intake
The question of what disease is caused by SE deficiency leads to multiple answers, with severe, localized deficiencies resulting in conditions like Keshan and Kashin-Beck diseases. For the wider population, insufficient SE intake poses a risk to critical systems, including cardiovascular, immune, and thyroid health. Maintaining adequate, but not excessive, selenium levels through a balanced diet is fundamental for preventing these health issues and ensuring the proper functioning of essential selenoproteins. For regions with low soil selenium, public health strategies like supplementing animal feed or fertilizers can be highly effective. For those concerned about their intake, a consultation with a healthcare provider can help determine if supplementation is necessary.
Learn more about the broader roles of selenium in human health.
