There are several causes for high thyroid levels, also known as hyperthyroidism or overactive thyroid. The thyroid is an endocrine gland in the neck that produces hormones that are used in many areas of the body. Because thyroid hormones are used in various physiologic processes, high levels of thyroid hormones can have many different side effects.
Causes
According to the American Thyroid Association, the most common reason for hyperthyroidism is Graves' disease, an autoimmune condition where the thyroid produces excess thyroid hormone. High thyroid levels can also come from thyroid nodules that are producing thyroid hormone. Thyroiditis is an inflammation in the thyroid that can produce hyperthyroidism. High thyroid levels can also be caused by medications such as levothyroxine, the hormone used to treat an underactive thyroid. Too much levothyroxine can lead to elevations in thyroid hormone. Other medications, like amiodarone and lithium, can also cause high thyroid levels
Cardiac Effects
No matter what the cause, too much thyroid hormone can be hard on the heart. The American Association of Clinical Endocrinologists (AACE) states that hyperthyroidism can lead to enlargement of the heart and an arrhythmia known as atrial fibrillation. Patients may feel have palpitations, feel like their heart is racing or have problems with exercise. These effects are more pronounced in elderly patients.
Bone Loss
Patients with high thyroid levels often experience bone loss. This can lead to osteoporosis or a pre-osteoporosis condition called osteopenia. Both levels of bone loss increase the risk of fractures. Bone loss due to hyperthyroidism is most commonly seen in menopausal women.
Eye Disease
Thyroid eye disease is most common in patients with Graves' hyperthyroidism. The eyes may feel irritated, appear red and protrude from the face. This can be permanent, even once thyroid levels return to normal after treatment. Patients may require treatment with steroids, radiation or surgery to correct thyroid eye disease.
Other Side Effects
According to AACE, hyperthyroidism can also lead to weight loss, nervousness, diarrhea, tremor, difficulty sleeping, tiredness, difficulty concentrating, sweating and irregular menstrual periods in women.
