Final answer:
Selenium deficiency is linked to Keshan disease, affecting the heart and causing cardiomyopathy. It also impacts the immune system and thyroid function.
Step-by-step explanation:
Selenium deficiency has been associated with Keshan disease, a condition characterized by heart problems, particularly a type of heart muscle disease known as cardiomyopathy.
Selenium is an essential trace mineral required for the proper functioning of certain enzymes involved in antioxidant processes that protect cells from damage. Additionally, a lack of selenium can compromise immune system functions and may lead to thyroid dysfunction.