The thyroid gland is a small, hormone-secreting gland in the base of the neck that is similar in shape to a butterfly. Diseases of the thyroid gland, sometimes called thyroidism, often develop in two forms. Hyperthyroidism is the result of the thyroid producing too much hormone, which increases the body's rate of metabolism. In contrast, hypothyroidism occurs when the thyroid produces too little hormone, causing a sluggish metabolism. Different factors usually lead to the different forms of thyroidism, although there are some overlapping causes.
Autoimmune Conditions
An inflamed and swollen thyroid glad is the most common cause of both hyperthyroidism and hypothyroidism. An inflamed thyroid, also known as thyroiditis, can occur for several reasons. Autoimmune conditions, caused by the immune system mistakenly attacking the thyroid, are the most common cause of thyroiditis leading to thyroidism, according to the National Endocrine and Metabolic Diseases Information Service. Graves' disease, also called toxic diffuse goiter, occurs when the immune system creates an antibody that activates the thyroid gland. The hyperactive thyroid gland produces too much hormone, which causes hyperthyroidism. In contrast, in Hashimoto's thyroiditis, the immune system attacks and destroys the thyroid gland, leading to hypothyroidism because the thyroid cannot produce enough hormone. Several other, less common autoimmune disorders can also cause hypo- or hyperthyroidism.
Postpartum Thyroiditis
Approximately five to nine percent of women who give birth experience a temporary swollen thyroid, reports the Cleveland Clinic. Depending on how the thyroid reacts, postpartum thyroiditis can either cause the thryroid to become overactive, causing hyperthyroidism, or underactive, causing hypothyroidism. These postpartum thyroid problems usually disappear after a few weeks.
Medical Treatment
Several different types of medical treatments can lead to thyroidism. If cancer develops in the thyroid gland, a portion or all of the thyroid may need to be removed. This surgical removal of the thyroid will cause hypothyroidism, because the thyroid cannot secrete the needed hormones, explains the Endocrine Web. Radiation therapy to treat cancers in the neck can also damage the thyroid and prevent it from making enough hormone. Some medication, such as amiodarone, lithium and propylthiouracil can decrease thyroid function and cause hypothyroidism. In the opposite case, treating a patient with too much thyroid hormone to treat hypothyroidism can sometimes go too far and cause hyperthyroidism.
Iodine
Ingesting the improper amount of iodine can cause thyroid problems. They thyroid gland needs iodine in order to create its hormones. If insufficient iodine is eaten, the thyroid cannot make enough hormone, and hypothyroidism occurs. This condition afflicts nearly 100 million people around the world, according to the Cleveland Clinic. On the opposite end of the spectrum, eating too much iodine or taking medications that contain large amounts of iodine can cause the thyroid to produce excess hormone, resulting in hyperthyroidism.
