Many of our organs' functions and metabolism are controlled by hormones secreted by a small, butterfly shaped gland known as the thyroid gland. It is located it the front of the neck, slightly above the top of the chest bone.
If the thyroid gland somehow gets into overdrive, it will produce too much thyroid hormone. This condition is known as hyperthyroidism. It speeds up chemical reactions in the body in a bad way and causes undesired mental and physical changes.
Surplus of thyroid hormones is toxic condition known as thyrotoxicosis. About eight percent of population suffer from over-functioning of the thyroid gland, and women are far more prone to develop this condition. If left untreated, hyperthyroidism may eventually lead to fatal abnormalities of heart rhythm or osteoporosis.
A common cause for hyperthyroidism is an autoimmune condition. Normally, the organism's immune system (defence system if you will) only targets foreign objects, such as viruses, bacteria and parasites, or various undesired particles that somehow get inside us. For reasons still unknown, immune system of some people can get the wrong idea and start to attack the organism itself, be it cells, tissues or organs. In this case, the defence systems attack the thyroid gland, but instead of destroying it (as is case in, say rheumatoid arthritis when attacks damage cartilage and tissues around the joints), these attacks just stimulate the gland and it begins to produce too much hormones.
Most common cause of hyperthyroidism is autoimmune disease known as Grave's disease. Other reasons include hyperthyroidism induced by treatment, by medications or by thyroid hormone preparations (sometimes used as means of achieving weight loss by accelerating metabolism). Excess intake of iodine, through diet, exposure to a radiographic contrast media (used in various medical tests) or through medications is also common cause of hyperthyroidism. Typical American way to excess iodine is by Amiodarone, a drug used for arrhythmia.
Herbal treatment may slow progress of disease, restore the balance of the immune system and soothe symptoms of hyperthyroidism.
Some herbs block the receptors for thyroid-stimulating hormone on the thyroid, thus preventing the gland from overproduction of hormones. These are common gromwell (Lithospermum officinale) and Lemon balm (Melissa officinalis) and plants from the Gypsywort family (Lyucopus ssp).
What to avoid
Seaweeds such as kelp, bladderwrack and other contain high amounts of iodine and should not be consumed in excess quantities. Thyroid hormone levels may be raised by ashwaghanda plant.