What is the Thyroid Gland?
The Thyroid is located in the mid neck in front of the wind pipe and larynx, below the Adams apple. It is one of the first glands created in the body, during 3-4 weeks of gestation the thyroid will appear below the tongue, and will migrate down the neck over the next 6-8 weeks. This endocrine gland produces hormones that helps with growth, metabolism (the rate that our bodies use energy), rate at which other system function, and how sensitive the body is to other hormones. The thyroid also acts as a iodine absorber, and uses iodine and tyrosine to create the hormones T3 and T4.
Hormones of the Thyroid
Triiodothyronine (T3): Produced in the epithelial cells this is the more potent version of the thyroid hormone. It stimulates RNA polymerase 1 and 2 promoting protien synthesis and it stimulates body energy and oxygen consumption which increases the basal metabolic rate.
Thyroxine (T4):The weaker form of the thyroid hormone it works the same as T3 but having a smaller effect.
Calcitonin:: Produced in the parafollicular cells this hormone encourages bone growth through stimulating osteoblasts, as well inhibits bone release of Ca2+ (calcium) reducing the amount of blood calcium.
The Hypothalamus and Pituitary are responsible for moderating the Thyroid and unlike other glands in the endocrine system, does not itself monitor blood levels in the body, only absorbing iodine through a complex process of trapping it with hydrogen peroxide developed by an enzyme thyroid peroxidase. The hormones secreted by the thyroid play a big part in brain maturation during gestation, as well continues to play a big role in brain health throughout our lives. The Thyroid is a burdened gland, and commonly suffers from diseases such as hyperthyroidism (overactive) and hypothyroidism (under active), cancers and immune disorders.
Cells of the Thyroid
Epithelial cells: A single layer of epithelial cells surround the follicles and secrete T3 and T4. Actually changing cell structure while not releasing T3/T4 from tall columnar cells to low columnar and cuboidal cells.
Parafollicular: Amongst the follicles and between spherical follicles the parafollicular cells secrete calcitonin.
Follicles: These spherical follicles absorb iodine in the ion form from the blood and produce (synthesize) the thyroid hormones. The follicles store the raw materials for hormone synthesis in the thyroid to some extent reserve the hormones themselves in the colloids a rich protein called thyroglobulin, that lies inside the follicles.
