Causes of high thyroid-stimulating hormone, or TSH, levels include hypothyroidism, excess anti-thyroid medication and a tumor in the pituitary gland, according to LabTestsOnline. TSH is produced in the pituitary gland, and it is partly responsible for energy metabolism, so high levels indicate dysfunction in either the thyroid or pituitary gland.
Hypothyroidism is a common disorder that occurs when there is a lack of thyroid hormone in the body, explains Cleveland Clinic. The most common cause of this condition is Hashimoto's disease, in which the body's immune system attacks the thyroid gland. Other causes of hypothyroidism include an inflamed thyroid after an illness or pregnancy, certain medications and a problem with the pituitary gland. Symptoms of hypothyroidism include weight gain, fatigue and dry skin and hair.
Patients with hyperthyroidism are given antithyroid medication to alleviate their symptoms, which can lead to high TSH levels if too much medication is taken, notes LabTestsOnline.
Hyperthyroidism occurs when the thyroid gland produces too much thyroid hormone, according to Cleveland Clinic. The condition has several causes, including Graves' disease, thyroid nodules and inflammation of the thyroid. Graves' disease is a hereditary disorder, and it is the most common cause of hyperthyroidism. Symptoms of hyperthyroidism include diarrhea, weight loss and a rapid heartbeat.
A pituitary gland tumor can cause hypothyroidism, leading to high TSH levels, explains Barrow Neurological Institute. Patients with a pituitary gland tumor that leads to excessive TSH levels experience fatigue,hand tremors, vision loss and headache.