Brain Basics^™ - Ultra-Pure Selenomethionine is the most bioavailable form of selenium. Selenomethionine has been shown to be essential for proper thyroid function in particular conversion of T4 to T3 the active form of the thyroid hormone. It has also been found to support the immune system. Research studies have found that maintaining normal serum selenium levels is associated with support for normal cellular function, proper cell division, as well as healthy heart, connective tissue, eye and hepatic function.*