The thyroid is a small, butterfly-shaped gland at the front of the neck. It produces hormones that help regulate metabolism, heart rate, temperature, and other body functions. When the gland produces too little thyroid hormone, the condition is called hypothyroidism. When it produces too much, it is called hyperthyroidism. The causes differ, so assessment by a healthcare professional is important.
Common Causes of Hyperthyroidism
Hyperthyroidism occurs when the body has too much thyroid hormone. Common causes include:
- Graves’ disease: An autoimmune condition that stimulates the thyroid to make excess hormone. It is a common cause of hyperthyroidism. Learn more about Graves’ disease.
- Overactive thyroid nodules: One or more nodules can make thyroid hormone independently of the gland’s usual control signals.
- Thyroiditis: Inflammation can release stored hormone into the bloodstream. Some forms are temporary, although the course depends on the cause.
- Excess iodine or certain medicines: In susceptible people, high iodine exposure or medicines such as amiodarone can affect thyroid function.
- Less common causes: Rarely, problems involving the pituitary gland or other conditions can lead to excess thyroid hormone.
Common Causes of Hypothyroidism
Hypothyroidism develops when the thyroid does not make enough hormone. Possible causes include:
- Hashimoto’s thyroiditis: An autoimmune condition in which the immune system damages thyroid tissue over time.
- Thyroid surgery or radioactive iodine treatment: Removing or treating part or all of the thyroid can reduce hormone production.
- Medicines: Lithium and some other medicines can affect thyroid function.
- Iodine imbalance: Too little iodine can contribute to hypothyroidism, while excessive iodine can also disrupt thyroid function in some people.
- Thyroiditis: Some forms of thyroid inflammation can cause a temporary period of low thyroid hormone, and some people develop longer-lasting hypothyroidism.
- Less common causes: Conditions affecting the pituitary gland, or rarely certain cancers and their treatments, can interfere with thyroid hormone levels.
How Are Thyroid Problems Treated?
Treatment depends on the diagnosis, thyroid blood-test results, symptoms, other health conditions, and the underlying cause. Hypothyroidism is commonly treated with prescribed thyroid hormone replacement. Hyperthyroidism may be managed with antithyroid medicines, radioactive iodine, surgery, or other treatment depending on the cause. Medicines such as beta blockers can sometimes help control symptoms, but they do not correct every cause of hyperthyroidism.
Do not start, stop, or change thyroid medicine or supplements on your own. Desiccated thyroid products and iodine supplements are not suitable for everyone, and thyroid treatment needs medical supervision and follow-up testing.
When Should You Seek Medical Advice?
Symptoms such as unexplained weight changes, unusual tiredness, sensitivity to heat or cold, changes in heart rate, tremor, or changes in bowel habits can have many causes. If you are concerned, speak with a healthcare professional. Blood tests, often including TSH and thyroid hormone levels, can help determine whether the thyroid is involved.
For more background, read our guide to how thyroid hormones affect the body. This article is for general information and is not a substitute for individual medical advice.