Thyroid

The thyroid gland is regulated by thyroid-stimulating hormone (TSH), which is made by the pituitary gland in the brain. Normally, when thyroid hormone levels in the body are high, they will "switch off" the production of TSH, which in turn stops the thyroid Causes
Thyroid diseases sometimes result from inappropriate TSH levels, or may be caused by problems in the thyroid gland itself.Another form of hyperthyroidism is called toxic nodular goiter or toxic thyroid adenoma. Adenomas, abnormal nodules of tissue in the thyroid, constantly produce thyroid hormones even when they are not needed.

Secondary hyperthyroidism is caused when the pituitary gland makes too much TSH, leading to constant stimulation of the thyroid gland. A pituitary tumour may cause TSH levels to rise. More rarely, the pituitary gland becomes insensitive to thyroid hormones, no longer responding to high levels.

Another possible cause of hyperthyroidism is a condition called thyroiditis. This condition occurs when the thyroid gland becomes inflamed. Depending on the type of thyroiditis, this may lead to temporary hyperthyroidism that might be followed by hypothyroidism.

The most common cause of hypothyroidism is Hashimoto's thyroiditis, an autoimmune condition where the body makes antibodies that destroy parts of the thyroid gland. Surgical removal and certain medications (e.g., amiodarone, lithium) can also cause hypothyroidism.

Other causes of hypothyroidism include pituitary problems, hypothalamus problems, and iodine deficiency (rare in North America, but affects nearly 2 billion people