This is a condition in which the thyroid gland is overactive and produces too much of the thyroid hormones. This can happen due to a variety of reasons:

• Graves’ disease: This is an autoimmune disease in which the immune system attacks the thyroid cells and causes the overproduction of the hormones. It is the most common cause of hyperthyroidism, affecting 1 in every 200  in the United States. The cause of this is unknown.

• Plummer’s disease: Sections of the thyroid gland develop non- cancerous lumps which make it grow larger, hence producing too much T4.

• Thyroiditis: This condition causes excessive swelling of the thyroid gland, forcing hormones into the bloodstream.

These conditions can cause arrythmias, weight loss, tremors, anxiety, etc.