Thyroid Gland: A Breif View

The thyroid gland is small endocrine gland located in the front of the wind pipe in the throat. It produces the thyroid hormones triiodothyronine and thyroxine which increase cellular metabolism as well as other functions such as our heart rate, how quickly we burn calories, digestion etc Babies and children need adequate amounts of thyroid hormones for brain development and growth. The amount of thyroid hormones secreted is controlled by another hormone, called thyroid stimulating hormone (TSH), which is released from the pituitary gland in your head.

Thyroid gland is composed of follicles. Follicles are lined by a single layer of epithelial cells. They are filled with an amorphous colloidal material.There are two cell types in the thyroid gland:
Follicular cells and
Parafollicular cells.

Follicular cells release and store thyroid hormone. Parafollicular cells of the thyroid gland are also called C cells. The parafollicular cells secrete calcitonin.

The thyroid itself is regulated by another gland located in the brain, called the pituitary. In turn, the pituitary is regulated in part by thyroid hormone that is circulating in the blood and in part by another gland called the hypothalamus, also a part of the brain.

The hypothalamus releases a hormone called thyrotropin releasing hormone which sends a signal to the pituitary to release thyroid stimulating hormone. In turn, TSH sends a signal to the thyroid to release thyroid hormones. If over activity of any of these three glands occurs, an excessive amount of thyroid hormones can be produced, thereby resulting in hyperthyroidism.

The rate of thyroid hormone production is controlled by the pituitary gland. If there is an insufficient amount of thyroid hormone circulating in the body to allow for normal functioning, the release of TSH is increased by the pituitary in an attempt to stimulate the thyroid to produce more thyroid hormone. In contrast, when there is an excessive amount of circulating thyroid hormone, the release of TSH is reduced as the pituitary attempts to decrease the production of thyroid hormone.

Thyroid hormones stimulate the metabolism of cells. The thyroid gland removes iodine from the blood and uses it to produce thyroid hormones.Hyperthyroidism is a condition in which an overactive thyroid gland is producing an excessive amount of thyroid hormones that circulate in the blood. During pregnancy, the hormone HCG is produced which increases to a peak at around 12 weeks. It has mild thyroid stimulating effects and as a result, can cause some symptoms of hyperthyroidism. In situations of multiple pregnancies HCG levels are even higher, and symptoms can be more pronounced. Temporary hyperthyroidism occurs in 10-20% of normal pregnant women during this period, and these women typically do not require treatment.