What is hyperthyroidism?

Hyperthyroidism is a condition in which the thyroid gland (a small, butterfly-shaped gland in the front of the neck) makes too much thyroid hormone. Thyroid hormone helps control your body’s metabolism. If you make too much thyroid hormone, different functions in your body and your metabolism speed up.

What causes hyperthyroidism?

  • An autoimmune disorder, such as Graves’ disease (this is the most common cause of hyperthyroidism)
  • One or more thyroid nodules (growth/s within the thyroid gland) that make excess thyroid hormone
  • Inflammation of the thyroid gland (acute or subacute thyroiditis)
  • Over-treatment of an underactive thyroid (if too much thyroid hormone is taken for replacement)
  • Genetic conditions and rare ovarian tumors
  • Very rarely, a tumor in the pituitary gland (a small gland in the brain that controls other glands in the body) that make an excess of a hormone called thyroid stimulating hormone (TSH) that pushes the thyroid gland to make too much thyroid hormone

Thyroid storm is a rare, but very serious type of hyperthyroidism in which thyroid hormone levels are extremely high. This can be life-threatening.

What are the Signs and Symptoms of Hyperthyroidism?

The clinical features of hyperthyroidism are different for every person. Common signs and symptoms include:

  • Nervousness or irritability
  • Weight loss
  • Increased appetite
  • More bowel movements than usual
  • Trouble sleeping
  • Sensitivity to hot temperatures
  • Sweating more than usual
  • Fatigue (tiredness)
  • Muscle weakness
  • Palpitations (from a very fast heart rate)
  • High blood pressure
  • Hand tremors (shakiness of hands)
  • Thinning of the skin
  • Fine, brittle hair
  • Prominent eyes
  • Irregular or lighter menstrual periods (in girls)
  • Enlarged thyroid gland (goiter)
  • Brisk reflexes
Rev. 11/2019. MassGeneral Hospital for Children and Massachusetts General Hospital do not endorse any of the brands listed on this handout. This handout is intended to provide health information so that you can be better informed. It is not a substitute for medical advice and should not be used to treatment of any medical conditions.