What are the thyroid and parathyroid glands? The thyroid gland is a butterfly-shaped endocrine gland located anterior and inferior to the larynx. It produces two types of hormones; the iodine-containing hormones tri-iodothyronine (T3), thyroxine (T4), and calcitonin. The parathyroid glands are four small ovoid glands located on the posterior surface of the thyroid gland. They are responsible for secreting parathyroid hormone (PTH).