Thyroid Gland, Thyroxine, Hypothyroidism and Hyperthyroidism

What is the Thyroid?

The thyroid is a relatively small gland found in the base of the neck, located just below the “Adam’s apple.” The thyroid produces hormones that travel through the blood and control the rate of many activities in your body, including how fast your heart beats and how quickly you burn calories. In other words, the thyroid plays a large role in controlling your metabolism.

What is thyroxine?

Thyroxine is the main hormone secreted into the bloodstream by the thyroid gland. It is the inactive form and most of it is converted to an active form called triiodothyronine by organs such as the liver and kidneys. Thyroid hormones play vital roles in regulating the body’s metabolic rate, heart and digestive functions, muscle control, brain development and maintenance of bones.

How is thyroxine controlled?

The production and release of thyroid hormones, thyroxine and triiodothyronine, is controlled by a feedback loop system that involves the hypothalamus in the brain and the pituitary and thyroid glands. The hypothalamus secretes thyrotropin-releasing hormone which, in turn, stimulates thepituitary gland to produce thyroid stimulating hormone. This hormone stimulates the production of the thyroid hormones, thyroxine and triiodothyronine, by the thyroid gland.

This hormone production system is regulated by a feedback loop so that when the levels of the thyroid hormones (thyroxine and triiodothyronine) increase, they prevent the release of both thyrotropin-releasing hormone and thyroid stimulating hormone. This system allows the body to maintain a constant level of thyroid hormones in the body.

Hyperthyroidism

When the thyroid produces more thyroid hormones than the body needs, that is the definition of hyperthyroidism, or overactive thyroid. The most common cause of hyperthyroidism Is Graves’ disease, a disorder where the body’s immune system stimulates the thyroid too much.

Symptoms of hyperthyroidism usually begin slow, making them hard to notice. Over time an excessive metabolism may result in unwanted/unhealthy weight loss, rapid or irregular heartbeat, irritability, anxiety, trouble sleeping, increased sweating, muscle weakness and less frequent menstrual periods for females.

Hypothyroidism

When the thyroid does not produce enough thyroid hormones for the body, that is the definition of hypothyroidism, or underactive thyroid. The most common cause of hypothyroidism is Hasimoto’s disease, a disorder where the immune system actually attacks the thyroid. Other causes of hypothyroidism can include thyroid removal, some radiation treatment of certain cancers and even treatment for hyperthyroidism.

Symptoms of hypothyroidism usually begin slow, making them hard to notice. At first you may just feel a little tired or sluggish. Other symptoms that may develop later include uncontrolled weight gain, joint or muscle pain, increased sensitivity to cold, depression, pale skin, a puffy face, a hoarse voice and excessive menstrual bleeding for females.

If you suspect you may have any issues with your thyroid gland, it’s important that you see a thyroid specialist as soon as possible to avoid complications with hyperthyroidism or hypothyroidism.