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Hypothyroidism occurs when the thyroid gland fails to produce enough thyroid hormone. Without enough thyroid hormone, the body becomes tired and run down. Every organ system slows, including the brain, which affects concentration; the gut, causing constipation; and metabolism – the rate at which the body burns energy – resulting in weight gain. Although there are many different causes of hypothyroidism, the resulting effect on the body is the same.

The most common cause of hypothyroidism is Hashimoto's thyroiditis, a disease in which the body's immune system attacks the thyroid gland. Failure of the pituitary gland to secrete a hormone to stimulate the thyroid gland, called secondary hypothyroidism, is a less common cause of hypothyroidism. Other causes include congenital defects, surgical removal of the thyroid gland, irradiation of the gland and inflammatory conditions.

The condition is more common in women and people over the age of 50. Other risk factors include thyroid surgery and exposure of the neck to X-ray or radiation treatments.

Our approach to hypothyroidism

UCSF offers comprehensive consultations and care for thyroid conditions, including hypothyroidism (underactive thyroid). For this condition, we prescribe thyroid hormone and adjust the dose until normal levels are reached. With proper treatment, patients with hypothyroidism can eliminate symptoms.

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Signs & symptoms

Symptoms of hypothyroidism depend on the decrease in thyroid hormone and the duration of the condition. Often, mild symptoms are mistaken for other problems. Symptoms may include:

  • Fatigue
  • Joint or muscle stiffness
  • Decreased hearing
  • Weight gain
  • Dry skin
  • Sensitivity to cold
  • Coarseness or loss of hair
  • Goiter, or an enlarged thyroid causing a lump in the neck
  • Constipation
  • Memory and mental impairment
  • Depression and irritability
  • Irregular or heavy menstruation
  • Slowed heart rate
  • Decreased libido


The most effective and efficient way to diagnose hypothyroidism is by measuring the thyroid stimulating hormone (TSH) level in your blood, which will be high if you have the disease. At the same time, the thyroid hormones, T4 and T3, will be low.

Other tests may be performed to determine the cause of hypothyroidism, including measuring thyroid antibody levels.


Since patients with hypothyroidism have deficient levels of thyroid hormone, treatment for the condition focuses on hormone replacement therapy. One example of hormone replacement treatment is the hormone pill levothyroxine, which is taken once a day, preferably in the morning.

Although thyroid hormone drugs produce no allergic reactions, their effectiveness may be decreased by interactions with other drugs or food supplements. It's important that you tell your doctor about other drugs and supplements you're taking.

UCSF Health medical specialists have reviewed this information. It is for educational purposes only and is not intended to replace the advice of your doctor or other health care provider. We encourage you to discuss any questions or concerns you may have with your provider.

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