People with chronic fatigue syndrome who have autoantibodies targeting selenoprotein P show lower levels of markers indicating thyroid hormone conversion to its active form, compared to those without these autoantibodies.

In people with chronic fatigue syndrome, those with specific antibodies against selenoprotein P show lower levels of a combined measure of thyroid hormone activation and iodine intake than those without these antibodies, suggesting this combination may help identify impaired thyroid function.

People with chronic fatigue syndrome who have specific antibodies targeting selenoprotein P excrete less iodine in their urine than those without these antibodies or healthy individuals, suggesting a reduction in the release of iodide from thyroid hormones caused by decreased deiodinase enzyme function.

A specific type of antibody that targets selenoprotein P is found in a higher percentage of people with chronic fatigue syndrome than in people without the condition.

In people with chronic fatigue syndrome who have specific autoantibodies, selenium in the blood does not correlate with the activity of an enzyme called glutathione peroxidase 3, suggesting that selenium is not reaching the kidneys properly even though overall selenium levels in the body are normal.