Download The thyroid gland, the largest endocrine gland, is

The thyroid gland, the largest endocrine gland, is responsible for the
production of the hormones T3, T4, and calcitonin.
LEARNING OBJECTIVE [ edit ]
Describe the hormones produced by the thyroid and explain how their production is regulated
KEY POINTS [ edit ]
The thyroid gland is made up of thyroid follicles, which produce three main hormones.
T3 and T4 hormones increase the metabolic activity of the body‘s cells while calcitonin helps
regulate calcium concentrations in body fluids.
T3 and T4 release is controlled by thyroid stimulating hormone; however, calcitonin release is
controlled by calciumion concentrations.
TERMS [ edit ]
triiodothyronine
the most powerful thyroid hormone, affecting almost every process in the body, including body
temperature, growth, and heart rate
thyrocalcitonin
a hormone, secreted by parenchymal cells, that regulates calcium and phosphate metabolism
thyroxine
a hormone (an iodine derivative of tyrosine), produced by the thyroid gland, that regulates cell
metabolism and growth
thyroglobulin
a globulin, produced by the thyroid gland, that has a role in the production of the thyroid
hormones
Give us feedback on this content: FULL TEXT [ edit ]
Thyroid Gland
The thyroid gland, one of the
largestendocrineglands in the body, is
located in the neck, just below the larynx
and in front of the trachea . It is a
butterfly­shaped gland with two lobes that
are connected by the isthmus. It has a
dark red color due to its extensive
vascular system. When the thyroid swells
due to dysfunction, it can be felt under the
skin of the neck.
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Thyroid gland
The location of the thyroid gland is in the neck below the larynx and in front of the trachea; it is the
largest endocrine gland in the body, producing T3, T4, and calcitonin.
The thyroid gland is made up of many spherical thyroid follicles which are lined with a
simple cuboidal epithelium. These follicles contain a viscous fluid, called colloid, which
stores the glycoprotein thyroglobulin. This glycoprotein is the precursor to the thyroid
hormones. The follicles produce hormones that can be stored in the colloid or released into
the surrounding capillary network for transport to the rest of the body via the circulatory
system.
The thyroid gland produces the hormones T3 (triiodothyronine) and T4 (thyroxine). These
hormones increase the metabolic activity of the body‘s cells. Follicle cells are stimulated to
release stored T3 and T4 by thyroid­stimulating hormone (TSH), which is produced by the
anterior pituitary. These thyroid hormones increase the rates of
mitochondrial ATP production.
Another hormone produced by the thyroid gland,thyrocalcitonin, or calcitonin, decreases the
concentration of calcium in the blood. Most of the calcium removed from the blood is stored
in the bones. Calcitonin is produced by parafollicular cells of the thyroid, either releasing
hormones or inhibiting hormones. The hormone's release is not controlled by TSH, but
instead is released when calcium ion concentrations in the blood rise. Calcitonin functions to
help regulate calcium concentrations in body fluids. It acts in the bones to
inhibit osteoclast activity and in the kidneys to stimulate excretion of calcium. The
combination of these two events lowers body fluid levels of calcium.