Final answer:
The trace mineral critical for the synthesis of thyroid hormone is iodine. It is required for the formation of T3 and T4 hormones by the follicular cells of the thyroid. Inadequate iodine intake can lead to iodine deficiency disorders such as goiter.
Step-by-step explanation:
The trace mineral critical for the synthesis of thyroid hormone is iodine. The follicular cells of the thyroid require iodides (anions of iodine) in order to synthesize T3 and T4 hormones, which are involved in cellular oxidation, growth, reproduction, and the activity of the central and autonomic nervous systems. Inadequate iodine intake can lead to iodine deficiency disorders such as goiter. Iodine can be obtained from the diet, and in some countries, iodine is added to table salt to ensure adequate intake.