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Thyroid Disease

An Overview of Hypothyroidism and Hyperthyroidism

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Updated July 26, 2012

PCOS and thyroid disease are two diseases that are often considered when a woman goes to her doctor with missing periods and abnormal hair growth. Hypothyroidism and hyperthyroidism are the two types of thyroid disease which doctors will test for when deciding between thyroid disease and PCOS.

Hyperthyroidism

Pathophysiology

The pituitary gland in the brain produces a hormone called Thyroid Stimulating Hormone (TSH), which goes to the thyroid and stimulates it to secrete Thyroid Hormones (known as T3 and T4). On the thyroid are proteins called receptors, which actually receive TSH and allow it to stimulate production of T3 and T4. Graves Disease, one cause of hyperthyroidism, occurs when antibodies are produced against those receptors, increasing the amount of T3 and T4 produced. Other causes of hyperthyroidism include thyroid cancer and increased secretion of TSH from the pituitary gland.


Symptoms

Because thyroid hormones are instrumental in many aspects of metabolism, many symptoms are characteristic of hyperthyroidism. Here are the most common:

  • enlarged thyroid gland
  • amenorrhea
  • weight loss/increase in appetite
  • excessive sweating
  • heat intolerance
  • temporary hair loss/ hair that is soft and fine
  • protrusion of the eyeballs
  • increased heart rate and blood pressure
  • insomnia

Diagnosis

The doctor will ask you questions about your symptoms and do a physical exam. He will also run blood work to test levels of TSH, T3, T4, and antithyroid antibodies. Typically, TSH is lower than normal, while T3 and T4 may be elevated.

Treatment

Today, there are many options for treatment of hyperthyroidism. Speak with your doctor to determine which is most appropriate given your age, and diagnosis. Here are the most common approaches.

Medications: Anti-thyroid medications including propylthiouricil and methimazole, reduce the amount of thyroid hormone that your thyroid gland produces. You may need to be on this medication for a while, even if symptoms begin to clear up.

Radioactive iodine: Also a pill, this altered form of iodine is absorbed into your thyroid gland and begins to shrink the tissue. This can help reduce the symptoms that you experience. Because it can be difficult to control exactly how much tissue is reduced, you may need to take replacement thyroid hormone (usually Synthroid) to supplement.

Surgery: If you are not a candidate for medication or radioactive iodine, surgery can be performed to remove the thyroid gland. Special care is taken to preserve the pararthyroid glands, small glands on the thyroid which regulate calcium metabolism. You will need replacement thyroid hormone (usually Synthroid) for the rest of your life.

Hypothyroidism

Pathophysiology

This results when inadequate amounts of thyroid hormone (T3 and T4) is produced. In primary hypothyroidism, the loss of thyroid tissue typically causes the lack of hormone production. This occurs when the thyroid is removed usually due to cancer. If the pituitary gland fails to produce enough TSH, due to a pituitary insufficiency or tumor, this is called secondary hypothyroidism.

In addition to removal of the thyroid as in cancer, hypothyroidism may develop for a number of reasons. The most common cause is a deficiency of iodine, as iodine is necessary for the production of thyroid hormone. If there is not enough iodine present in the body, the thyroid gland enlarges as it works harder to get the necessary iodine. Hashimoto's disease is an immune disease where the body produces antibodies against the cells and tissue of the thyroid gland. This leads to a diminished amount of thyroid hormone production. Certain medications such as lithium can affect thyroid function as well. If you are concerned about any of the medications you are taking, consult your doctor for more information.

Symptoms

Symptoms of hypothyroidism include the following:

  • cold intolerance
  • fatigue and lethargy
  • anovulation, which can cause irregular or infrequent periods
  • heavy or prolonged bleeding, which can also be caused by anovulation
  • decreased libido
  • weight gain despite decreased appetite
  • constipation
  • coarse, dry skin

Diagnosis

When diagnosing hypothyroidism, your physician or primary healthcare provider will most likely run a panel of thyroid hormones, including TSH, T3 and T4. In hypothyroidism, TSH is typically elevated, while blood concentrations of T4 may be decreased. A thorough history must also be considered when evaluating the results of your lab work.

Treatment

Hormone replacement therapy is usually the first line of treatment. By replacing the deficient hormones, the disease can be managed, and symptoms reversed. The drug most commonly prescribed is Synthroid (Levothyroxine). Dosages are prescribed according to lab work results, though doses of 50mcg through 200mcg is typical. Your doctor may want to routinely check your blood work to ensure that your dose does not need to be changed.



Sources:

Hypothyroidism. U.S. National Library and National Institute of Health: Medline Plus. Updated 12 May 2006. Accessed 6 February 2008. http://www.nlm.nih.gov/medlineplus/ency/article/000367.htm.

McCance, Kathryn L. and Huether, Sue E. Understanding Pathophysiology. Mosby. St. Louis MO, 2003. Pg 449-473.

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