This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: JIPMER 2017, Subject name: Biochemistry
Keshan's cardiomyopathy due to deficiency of: 
Select and explain. 
A. Chromium, B. Selenium, C. Magnesium, D. Copper
B: Selenium
Answer: B: Selenium 
Explanation: Selenium Selenium as selenocysteine is an essential component of the enzyme glutathione peroxidase Selenium containing enzyme 5'-deiodinase conves thyroxine (T4) to triiodothyronine in the thyroid gland. Thioredoxin reductase, involved in purine nucleotide metabolism Sources- seafood and meat, nuts Deficiency - Keshan's disease Toxicity - Selenium toxicity lead to Selenosis