Iodine is essential for what gland that controls growth and metabolism ?
Iodine is a micronutrient and dietary mineral that is naturally present in the food supply in some regions , especially near sea coasts , but is generally quite rare in the Earth 's crust , since iodine is a so - called " heavy " element ( with the highest atomic mass of any element needed by mammals for life ) , and abundance of chemical elements generally declines with greater atomic mass .