The thyroid is a small butterfly-shaped gland at the front of the neck, but it has a very important job.
It produces hormones that help control how the body uses energy, regulates body temperature, supports growth, and keeps many organs working properly.
When the thyroid does not make the right amount of hormones, it can affect almost every part of the body.
Millions of people around the world live with thyroid disorders. Some develop an underactive thyroid, known as hypothyroidism, while others have an overactive thyroid, called hyperthyroidism.
Because the symptoms often develop slowly and can be mistaken for other health problems, many people do not realise they have a thyroid condition until they are tested.
One of the most common causes of thyroid disease is an autoimmune disorder. Normally, the immune system protects the body from harmful germs. In autoimmune diseases, however, the immune system mistakenly attacks healthy tissues.
Hashimoto’s thyroiditis is the leading cause of hypothyroidism in many countries. In this condition, the immune system slowly damages the thyroid gland until it can no longer produce enough hormones. People often feel tired, gain weight, become sensitive to cold, develop dry skin, and notice slower thinking or low mood.
Graves’ disease is another autoimmune disorder, but it has the opposite effect. Instead of slowing the thyroid, it causes the gland to produce too much hormone. This speeds up the body’s metabolism and may lead to weight loss, a fast heartbeat, shaking, sweating, anxiety, and trouble sleeping.
Family history is also important. Researchers have discovered several genes that increase the chance of developing Hashimoto’s disease or Graves’ disease. Having these genes does not guarantee someone will become ill, but it does raise the risk, especially when combined with other factors.
Iodine is another key part of thyroid health because the body needs it to make thyroid hormones. Too little iodine can cause hypothyroidism, while too much iodine from supplements or certain foods may trigger thyroid problems in some people. This is why people should not take high-dose iodine supplements unless advised by a healthcare professional.
Environmental factors may also play a role. Exposure to high levels of radiation, some industrial chemicals, and certain pesticides has been linked to thyroid problems. Researchers continue to study how these exposures may affect thyroid cells over many years.
Women are much more likely than men to develop thyroid disease. Hormonal changes during pregnancy, after childbirth, and around menopause may influence thyroid function. Scientists believe female hormones interact with the immune system and the thyroid, although this relationship is still being investigated.
Some medicines and infections can also affect the thyroid. For example, lithium, which is used to treat bipolar disorder, can reduce thyroid function in some people. Viral infections may temporarily inflame the thyroid and change hormone levels until the gland recovers.
Smoking and long-term stress may further increase the risk in some individuals. Chemicals in cigarette smoke have been linked to Graves’ disease, while chronic stress may affect hormone balance and immune function. Although stress alone is unlikely to cause thyroid disease, it may contribute in people who are already at risk.
Treatment depends on the type of thyroid disorder. Hypothyroidism is usually managed with daily thyroid hormone tablets, while hyperthyroidism may be treated with medicines, radioactive iodine therapy, or surgery in selected cases. Regular blood tests help doctors adjust treatment and keep hormone levels within a healthy range.
This review shows that thyroid disorders are influenced by a combination of genetics, the immune system, hormones, lifestyle, and environmental factors.
One strength of current research is the growing understanding of how these factors interact, leading to better diagnosis and treatment. However, scientists are still working to explain exactly why autoimmune thyroid diseases develop and how they can be prevented.
Early diagnosis, regular medical care, and appropriate treatment remain the best ways to protect long-term health.
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