Thyroid epithelial cell
Encyclopedia
Thyroid epithelial cells (also called follicular cells or principal cells) are cells in the thyroid gland that are responsible for the production and secretion of thyroid hormones, that is, thyroxine
(T4) and triiodothyronine
(T3).
on the basolateral side, synthesize thyroglobulin
and thyroperoxidase from amino acids and secrete these into the thyroid follicles together with iodine. The thyroid epithelial cells can subsequently take up iodinated thyroglobulin from the follicles by endocytosis
, extract thyroid hormones from it with the help of protease
s and subsequently release thyroid hormones to the blood.
These thyroid hormones are transported throughout the body where they control metabolism (which is the conversion of oxygen and calories to energy). Every cell in the body depends upon thyroid hormones for regulation of their metabolism. The normal thyroid gland produces about 80% T4 and about 20% T3, however, T3 is about four times as potent as T4.
s. It is secreted into the follicle through the chloride/iodide transporter pendrin
on the apical side.
and are arranged in spherical follicles surrounding colloid.
They have thyrotropin receptor
s on their surface, which respond to thyroid-stimulating hormone
.
Embryologic origin is from a median endodermal mass in the region of the tongue (foramen cecum) in contrast to the parafollicular (C) cells that arise from the 4th branchial pouch.
-producing parafollicular cell
s (C cells) can be found scattered along the basement membrane
of the thyroid epithelium.
Embryologic origin of these C-cells is endodermal, from the ultimobranchial body
(4th pharyngeal pouch).
Thyroxine
Thyroxine, or 3,5,3',5'-tetraiodothyronine , a form of thyroid hormones, is the major hormone secreted by the follicular cells of the thyroid gland.-Synthesis and regulation:...
(T4) and triiodothyronine
Triiodothyronine
Triiodothyronine, C15H12I3NO4, also known as T3, is a thyroid hormone. It affects almost every physiological process in the body, including growth and development, metabolism, body temperature, and heart rate....
(T3).
Function
The thyroid epithelial cells take up iodine and amino acids from the blood circulationCirculatory system
The circulatory system is an organ system that passes nutrients , gases, hormones, blood cells, etc...
on the basolateral side, synthesize thyroglobulin
Thyroglobulin
Thyroglobulin is a 660 kDa, dimeric protein produced by and used entirely within the thyroid gland. In earlier literature, Tg was referred to as colloid....
and thyroperoxidase from amino acids and secrete these into the thyroid follicles together with iodine. The thyroid epithelial cells can subsequently take up iodinated thyroglobulin from the follicles by endocytosis
Endocytosis
Endocytosis is a process by which cells absorb molecules by engulfing them. It is used by all cells of the body because most substances important to them are large polar molecules that cannot pass through the hydrophobic plasma or cell membrane...
, extract thyroid hormones from it with the help of protease
Protease
A protease is any enzyme that conducts proteolysis, that is, begins protein catabolism by hydrolysis of the peptide bonds that link amino acids together in the polypeptide chain forming the protein....
s and subsequently release thyroid hormones to the blood.
These thyroid hormones are transported throughout the body where they control metabolism (which is the conversion of oxygen and calories to energy). Every cell in the body depends upon thyroid hormones for regulation of their metabolism. The normal thyroid gland produces about 80% T4 and about 20% T3, however, T3 is about four times as potent as T4.
Iodine transport
Iodine is taken up on the basolateral side of the thyroid epithelial cells by sodium-iodide symporterSodium-iodide symporter
The sodium/iodide symporter , also known as solute carrier family 5, member 5 is a protein that in humans is encoded by the SLC5A5 gene. The sodium/iodide symporter is a transmembrane glycoprotein with a molecular weight of 87 kDa and 13 transmembrane domains, which transports two sodium cations ...
s. It is secreted into the follicle through the chloride/iodide transporter pendrin
Pendrin
Pendrin also known as sodium-independent chloride/iodide transporter is a protein that in humans is encoded by the SLC26A4 gene .- Function :Pendrin is an ion exchanger found in the cortical collecting duct....
on the apical side.
Structure and development
They are simple cuboidal epitheliumEpithelium
Epithelium is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. Epithelial tissues line the cavities and surfaces of structures throughout the body, and also form many glands. Functions of epithelial cells include secretion, selective...
and are arranged in spherical follicles surrounding colloid.
They have thyrotropin receptor
Thyrotropin receptor
The thyrotropin receptor is a receptor that responds to thyroid-stimulating hormone and stimulates the production of thyroxine and triiodothyronine...
s on their surface, which respond to thyroid-stimulating hormone
Thyroid-stimulating hormone
Thyrotrophin-stimulating hormone is a peptide hormone synthesized and secreted by thyrotrope cells in the anterior pituitary gland, which regulates the endocrine function of the thyroid gland.- Physiology :...
.
Embryologic origin is from a median endodermal mass in the region of the tongue (foramen cecum) in contrast to the parafollicular (C) cells that arise from the 4th branchial pouch.
Relationship to other cell types
CalcitoninCalcitonin
Calcitonin is a 32-amino acid linear polypeptide hormone that is producedin humans primarily by the parafollicular cells of the thyroid, and in many other animals in the ultimobranchial body. It acts to reduce blood calcium , opposing the effects of parathyroid hormone . Calcitonin has been found...
-producing parafollicular cell
Parafollicular cell
Parafollicular cells are cells in the thyroid that produce and secrete calcitonin. They are located adjacent to the thyroid follicles and reside in the connective tissue. These cells are large and have a pale stain compared with the follicular cells or colloid...
s (C cells) can be found scattered along the basement membrane
Basement membrane
The basement membrane is a thin sheet of fibers that underlies the epithelium, which lines the cavities and surfaces of organs including skin, or the endothelium, which lines the interior surface of blood vessels.- Composition :...
of the thyroid epithelium.
Embryologic origin of these C-cells is endodermal, from the ultimobranchial body
Ultimobranchial body
The ultimopharyngeal body or ultimobranchial body or ultimobranchial gland is a small organ found in the neck region of many animals....
(4th pharyngeal pouch).