Hyperthyroidism is an excess production, release and activity of thyroid hormone from the thyroid gland. The thyroid is a part of the endocrine system as a whole, and is therefore solicited by and responding to the needs and demands of the body in any given moment and is in dance and relationship with all of the other hormones in the body. The job of the thyroid axis is to manage adaptability and growth. When a disease state has developed, and T4 and T3, the hormones made by the thyroid gland, are elevated in the blood stream, and there can be a number of symptoms associated (changes in temperature sensation and temperature tolerance, heart rate, weight loss, loose bowel movements or diarrhea, palpitations, anxiety/nervousness, insomnia and more). Hyperthyroidism, when severe, can lead to death, if not treated. Thyroid screening is generally a part of most screening bloodwork, though often only TSH is tested. A very low TSH will then generally prompt the additional testing of T3, T4 and possibly thyroid antibodies, especially if you symptoms are concerning for hyperthyroid. Some doctors will automatically run TSH, Free T3 and Free T4 as part of any screening tests. I also look at thyroid antibodies for many of my patients and other markers associated with overall thyroid functioning and thyroid’s interaction with other hormones in the body.
T4 increases the basal metabolic rate. It makes tissues more sensitive to dopamine and noradrenaline, which is part of the reason hyperthyroid symptoms can include an increased heart rate, arrhythmias, and feelings of anxiety. It stimulates the hollow organs and muscles, which can lead to diarrhea. Increased metabolic activity in the cells can lead to weight loss.
All of these are very appropriate and necessary actions of T4 when it is in healthy range, but in excess can cause the symptoms above.
T3 assists with the cell’s production of energy, again necessary, but when exaggerated can lead to the cells doing much more work than is sustainable, and the creation of more free radicals which can damage tissues.
Hyperthyroidism is diagnosed through a clinical history, physical exam and blood work. Blood work will show a very low TSH (thyroid stimulating hormone), and elevated free T4 and free T3 hormones. Part of the way the endocrine system regulates itself is through feedback mechanisms. TSH is the hormone made by the pituitary gland (in the brain), which signals the production and release of T4 and T3 from the thyroid gland (which sits in the throat). T4 and T3 are released into the bloodstream to have an effect on every cell in the body. TSH is also circulating in the blood stream. The pituitary receives information from the body, including the amount of circulating T4 and T3, and regulates the release of TSH accordingly. There are other factors involved in this process, for the sake of simplicity here, we’ll just look at that feedback loop. If T4 and T3 are adequate, TSH does not need to rise nor is it suppressed. If T4 and T3 are excessive, TSH is suppressed (lowered), to try to slow the whole cascade down. If T4 and T3 are low or insufficient, TSH will rise to signal the thyroid to make and release more hormone.
So, in hyperthyroid, we generally see a low TSH and a high T4 and T3 (all out of reference range).
Treatment will be more effective if it addresses both what is causing the thyroid to overproduce and release thyroid hormone as well as reducing the excess thyroid production and stimulation.
One of the things that can cause hyperthyroid is autoimmune thyroiditis.
Graves disease is an autoimmune condition, where antibodies bind to the thyroid gland and cause a production and release of thyroid hormone outside of the normal needs of the body.
Symptoms of Graves disease, especially if uncontrolled, may include a goiter (an enlarged thyroid gland which presents as a lump in the front of the throat and may also be felt on swallowing), pressure behind the eyes and possible protein buildup behind the eyes which causes them to begin bulging outward, and a thick swelling of the lower legs. There are other signs of excess thyroid activity which generally show up long before these symptoms and effective treatment can prevent these symptoms from occurring.
Treating the underlying causes of immune dysregulation, hyper immunity and development of the thyroid antibodies is important along with managing the thyroid activity in Graves.