Which mineral plays the biggest role in maintaining the thyroid gland structure and function?

The mineral that plays the biggest role in thyroid function is iodine. Iodine is involved in the synthesis of thyroid hormones by the iodination of tyrosine residues by the enzyme thyroid peroxidase forming either monoiodothyronine (MIT) or diiodothyronine (DIT). DIT can either join another DIT molecule to form thyroxine (T4) or an MIT molecule to form triiodothyronine (T3). If there is not enough iodine then thyroid hormones will not be produced and this will send a signal to the pituitary gland to make the thyroid gland enlarge to complensate for the thyroid function forming a goiter. 

That is true it is called an aftershock