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Hypothyroidism (Underactive Thyroid)

What Causes Hypothyroidism? continued...

Pituitary gland damage or disorder. Rarely, a problem with the pituitary gland can interfere with the production of thyroid hormone. The pituitary gland makes a hormone, called thyroid-stimulating hormone (TSH), which tells your thyroid how much hormone it should make and release.

Disorder of the hypothalamus. An extremely rare form of hypothyroidism can occur if the hypothalamus in the brain does not produce enough of a hormone called TRH. TRH affects the release of TSH from the pituitary gland.

Primary hypothyroidism is caused by a problem with the thyroid gland itself.

Secondary hypothyroidism occurs when another problem interferes with the thyroid's ability to produce hormones. For example, the pituitary gland and hypothalamus produce hormones that trigger the release of thyroid hormone. A problem with one of these glands can make your thyroid underactive.

Sometimes, an underactive thyroid that results from a problem with the hypothalamus is called tertiary hypothyroidism.

Who Is at Risk for Hypothyroidism?

Women, particularly older women, are more likely to develop hypothyroidism than men. You are also more likely to develop hypothyroidism if you have a close family member with an autoimmune disease. Other risk factors include:

Symptoms of Hypothyroidism

Symptoms of hypothyroidism may be vague and can often mimic other conditions. They may include:

  • Changes in the menstrual cycle
  • Constipation
  • Depression
  • Dry hair and hair loss
  • Dry skin
  • Fatigue
  • Greater sensitivity to cold
  • Slow heart rate
  • Swelling of the thyroid gland (goiter)
  • Unexplained weight gain or difficulty losing weight
  • Carpal tunnel syndrome

Babies with hypothyroidism may have no symptoms. If symptoms do occur, they can include:

  • Cold hands and feet
  • Constipation
  • Extreme sleepiness
  • Hoarse cry
  • Little or no growth
  • Low muscle tone (floppy infant)
  • Persistent jaundice (yellowing of the skin and whites of the eyes)
  • Poor feeding habits
  • Puffy face
  • Stomach bloating
  • Swollen tongue

Make an appointment with your health care provider if you or your baby has any of these symptoms. It is important to note that these symptoms can be due to other medical conditions.

How Is Hypothyroidism Diagnosed?

If you have symptoms of hypothyroidism, your doctor will order blood tests to check hormone levels. These may include:

  • Thyroid-stimulating hormone (TSH)
  • T4 (thyroxine)

Lower-than-normal T4 levels usually mean you have hypothyroidism. However, some people may have increased TSH levels while having normal T4 levels. This is called subclinical (mild) hypothyroidism. It is believed to be an early stage of hypothyroidism.

If your test results or physical exam of the thyroid are abnormal, your doctor may order a thyroid ultrasound, or thyroid scan, to check for nodules or inflammation.

WebMD Medical Reference

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