Without iodine the thyroid gland would not be able to function, and the resulting goitre would severely disrupt all metabolism.
A little background information
Iodine is a minor non-metallic mineral, qualified in nutrition as a trace element due to its low quantitative importance, although it is vital for the body.
Its role in the body
This trace element enters the body in the composition of the thyroid hormones, which it helps synthesise.
Sea salt and fish are the preferred sources of iodine.