Botanical Benefits A properly functioning thyroid gland controls growth, body temperature, metabolism, and mental and emotional balance. The thyroid’s workhorse is the hormone thyroxine. The thyroid releases thyroxine into the bloodstream to regulate body functions and metabolism. Iodine is essential for the production of thyroxine, therefore the thyroid is also the main storehouse for the body’s iodine. Mullein leaf and Lobelia are both adaptogenic herbs that aid the body to normalize function and increase the organ’s resistance to stress.