The thyroid gland, also known as the endocrine system gland that is located in the anterior part of the lower neck, below the larynx. The thyroid secretes hormones vital to metabolism and growth. Any enlargement of the thyroid, regardless of cause, is called a goiter.
In this video, we will introduce you the thyroid gland anatomy structure, function physiology, and thyroid hormone regulations.
Thyroid gland anatomy structure
The thyroid gland is a ductless alveolar gland found in the anterior neck, just below the laryngeal prominence also called adam’s apple. It is roughly butterfly-shaped, with two lobes wrapping around the trachea and connected in the middle by an isthmus. The thyroid gland is not usually palpable.
This the anterior view of the thyroid gland. and this is the posterior view of the thyroid gland.
It is supplied by superior and inferior thyroid arteries, drained via superior, middle and inferior thyroid veins, and has a rich lymphatic system.
Thyroid gland function physiology
The thyroid secretes several hormones, collectively called thyroid hormones. The main hormone is thyroxine, also called T4. Thyroid hormones act throughout the body, influencing metabolism, growth and development, and body temperature. During infancy and childhood, adequate thyroid hormone is crucial for brain development. T4 can only be made in the thyroid gland. It can then be converted by other tissues into T3.
The thyroid gland is also the site of the production of calcitonin, a hormone that can lower serum calcium concentrations.
Thyroid Hormone Release regulation
Thyroid hormones are released as part of the hypothalamic-pituitary-thyroid axis. The Hypothalamus detects a low plasma concentration of thyroid hormone and releases Thyrotropin-Releasing Hormone (TRH) into the hypophyseal portal system.
TRH binds to receptors found on thyrotrophic cells of the anterior pituitary gland, causing them to release Thyroid Stimulating Hormone (TSH) into the systemic circulation. TSH binds to TSH receptors on the basolateral membrane of thyroid follicular cells and induces the synthesis and release of thyroid hormone.