What is the thyroid?

The thyroid is a small gland, shaped like a butterfly, that rests in the middle of the lower neck. Its primary function is to control the body's metabolism (rate at which cells perform duties essential to living). To control metabolism, the thyroid produces hormones, T4 and T3, which tell the body's cells how much energy to use.

A properly functioning thyroid will maintain the right amount of hormones needed to keep the body's metabolism functioning at a satisfactory rate. As the hormones are used, the thyroid creates replacements.

The quantity of thyroid hormones in the bloodstream is monitored and controlled by the pituitary gland. When the pituitary gland, which is located in the center of the skull below the brain, senses either a lack of thyroid hormones or a high level of thyroid hormones, it will adjust its own hormone (TSH) and send it to the thyroid to tell it what to do.

What is thyroid disease?

When the thyroid produces too much hormone, the body uses energy faster than it should. This condition is called hyperthyroidism. When the thyroid doesn't produce enough hormone, the body uses energy slower than it should. This condition is called hypothyroidism. There are many different reasons why either of these conditions might develop.

Who is affected by thyroid disease?

Currently, about 20 million Americans have some form of thyroid disease. People of all ages and races can get thyroid disease. However, women are 5 to 8 times more likely than men to have thyroid problems.

What causes thyroid disease?

There are several different causes of thyroid disease. The following conditions cause hypothyroidism:

  • Thyroiditis is an inflammation of the thyroid gland. This can lower the amount of hormones produced.
  • Hashimoto's thyroiditis is a painless disease of the immune system that is hereditary.
  • Postpartum thyroiditis occurs in 5% to 9% of women after giving birth. It is usually a temporary condition.
  • Iodine deficiency is a problem affecting approximately 100 million people around the world. Iodine is used by the thyroid to produce hormones. Although prevalent before the 1950s in the United States, iodine deficiency has been virtually wiped out by the use of iodized salt.
  • A non-functioning thyroid gland affects one in 4,000 newborns. If the problem isn't corrected, the child will be physically and mentally retarded. All newborns are given a screening blood test in the hospital to evaluate thyroid function.

The following conditions cause hyperthyroidism:

  • With Graves' disease, the entire thyroid gland might be overactive and produce too much hormone. This problem is also called diffuse toxic goiter (enlarged thyroid gland).
  • Nodules might be overactive within the thyroid. A single nodule is called toxic autonomously functioning thyroid nodule, while several nodules are called a toxic multi-nodular goiter.
  • Thyroiditis, a disorder that can be painful or painless, can also release hormones that were stored in the thyroid gland causing hyperthyroidism for a few weeks or months. The painless variety occurs most frequently in women after childbirth.
  • Excessive iodine is found in a number of drugs such as Amiodarone, Lugol's solution (iodine), and some cough syrups, and might cause the thyroid to produce either too much or too little hormone in some individuals.

What are the symptoms of hypothyroidism and hyperthyroidism?

The following are symptoms for hypothyroidism:

  • Fatigue
  • Frequent, heavy menstrual periods
  • Forgetfulness
  • Weight gain
  • Dry, coarse skin and hair
  • Hoarse voice
  • Intolerance to cold

The following are symptoms for hyperthyroidism:

  • Irritability/nervousness
  • Muscle weakness/tremors
  • Infrequent, scant menstrual periods
  • Weight loss
  • Sleep disturbances
  • Enlarged thyroid gland
  • Vision problems or eye irritation
  • Heat sensitivity