Thyroid and Parathyroid Glands
The thyroid gland is in the front of the neck near the lower part of the larynx. The gland is about two inches and consists of two lobes, one on each side of the windpipe. The lobes are connected by tissue called the isthmus. The gland releases two hormones that contain iodine. The primary hormone is thyroxine (T4), the gland also releases a small amount of triiodothyronine (T3). These two hormones help regulate protein synthesis and ATP production. The gland needs iodine to produce these hormones, without it a goiter will develop, which is the swelling of the thyroid gland.
On the back of the thyroid gland are four parathyroid glands, two on each lobe. The parathyroid glands produce parathyroid hormone which helps regulate the levels of calcium and phosphate ions in the blood.