Definition of Hyperthyroidism:

Hyperthyroidism is a condition caused by an overactive thyroid gland. The gland makes too much T4 and T3 hormones. Hormones are substances that affect and control many important functions in the body.

Causes, incidence, and risk factors:

The thyroid gland is located in the neck. It produces several hormones which control the way that every cell in the body uses energy (metabolism). The thyroid is part of the endocrine system.

Hyperthyroidism or thyrotoxicosis occurs when the thyroid releases too many of its hormones over a short (acute) or long (chronic) period of time. Many diseases and conditions can cause this problem, including:

• Graves disease
• Non-cancerous growths of the thyroid gland or pituitary gland
• Tumors of the testes or ovaries
• Inflammation (irritation and swelling) of the thyroid due to viral infections or other causes
• Ingestion (taking in through the mouth, such as in eating) of large amounts of thyroid hormone
• Ingestion of excessive iodine

Graves disease accounts for 85% of all cases of hyperthyroidism.

Related topics:

• Painless (silent) thyroiditis
• Factitious hyperthyroidism
• Hypothyroidism
• Graves disease