Causes of thyroid disease

The cause of hypothyroidism disease can be autoimmune or non-autoimmune. 

• Autoimmune hypothyroidism. The immune system that protects the body against infection may mistake thyroid cells and their enzymes for foreign aggressors and attack them, leaving insufficient cells to produce the necessary amount of thyroid hormone. The most common form is Hashimoto's thyroiditis. 
• Non-autoimmune hypothyroidism. This is usually due to the partial or total removal of the thyroid by surgery, radioactive iodine treatment, congenital hypothyroidism, medication, iodine deficiency or excess, or pituitary disease.  

The cause of hyperthyroidism disease can be autoimmune or non-autoimmune.  

• Autoimmune hyperthyroidism. This is a result of Graves-Basedow disease in which the immune system synthesises antibodies that stimulate the thyroid gland to grow and produce excess thyroid hormones. The thyroid is diffusely enlarged but with no nodules.   
• Non-autoimmune hyperthyroidism. This is due to the presence of either one hyperfunctioning nodule (toxic nodule) or several hyperfunctioning nodules (toxic goitre).  A single nodule is termed a toxic autonomous thyroid nodule, while multiple nodules are referred to as a toxic multinodular goitre.