The Thyroid Gland
The thyroid gland is responsible for secreting two hormones which help regulate metabolism, promote growth and development, and aid in the activity of the nervous system. The thyroid gland is located in the lower neck, below the larynx and anterior to the trachea (Timby & Smith, 2013). It is divided into two lobes and joined by a band of tissue called the isthmus. The thyroid's major function is to concentrate iodine from dietary intake and synthesizing the two hormones tetraiodothyronine (thyroxin or T4) and triiodothyronine (T3). Calcitonin which also derives from the thyroid, is utilized to prevent the release of calcium from the bone into the extracellular fluid. Therefore, when there is a rise in calcium in the blood serum, the thyroid gland will release calcitonin to decrease the blood calcium levels by causing calcium to be stored in the bones. The thyroid is stimulated to release T3 and T4 by TSH (thyroid-stimulating hormone), hence the name, which is produced by the anterior pituitary gland (APG). When there is a low level of thyroid hormone in the blood, the hypothalamus will secrete TRH (thyrotropin-releasing hormone) which will then stimulate the production of TSH from the APG.
It's important to remember when teaching patients about diet is that adequate oral intake of iodine is necessary for the formation of thyroid hormones. Iodized salt is an option.