is the gland found at the base of the neck, which releases hormones that regulate the metabolic processes of cells.
gland secretes two main hormones that control the rate of bodily processes, thyroxine (T4) and triiodothyronine
(T3). Both are iodine containing hormone that controls the rate at which glucose is used up to provide energy for
the cells, which is also plays an important role in the growth and development of body systems. The only difference between
the two is the extra iodine atom found in thyroxine, which is also is secreted more regularly than T3.
of thyroid hormones is regulated by interactions between the hypothalamus in the brain, the pituitary gland, the thyroid gland,
and thyroid hormone levels in the body. When thyroid hormone levels are low, the hypothalamus is activated and sends signals
to the pituitary gland to release thyroid stimulating hormone (TSH). In turn, the thyroid gland releases thyroid hormones
until their levels in the body are normal. Once normal levels are reached, the hypothalamus’ detection is shut off,
and the cycle is shut down.
who live in areas where they can not receive sufficient iodine develop goiters. A goiter is an enlargement of the thyroid
gland due to the overproduction if incomplete thyroid hormones. When thyroid hormone levels are low, the pituitary gland keeps
sending TSH to the thyroid to produce T4 and T3, but the thyroid can not produce complete thyroid hormones
because it lacks the iodine required to create them. Therefore, the hypothalamus never gets the feedback signal to stop the
production of TSH, and the thyroid becomes enlarged in efforts to produce adequate amounts of thyroid hormone.
of thyroid hormones is described as hyperthyroidism, characterized by high metabolic rates, rapid heart and respiratory rates,
agitated behavior, and in some cases, protruding eyes.
thyroid hormone production is called hypothyroidism, characterized by sluggishness, obesity, low body temperature and poor
gland also produces calcitonin, which decreases calcium levels in the body by depositing it in the bones.