The thyroid is a gland located in the throat below the larynx. It is wrapped around the windpipe and releases hormones called thyroxine and triiodothyronine, also know respectively as T4 and T3. These hormones requires a chemical compound called iodine, which can be obtained through the diet or a supplement (if necessary), for their formation. T3 is released from the thyroid in much smaller amounts than T4, but acts upon the T4 to transform it into T3. T3 is the chemical that stimulates cellular metabolism. A low T3 concentration can lead to lowered metabolism.

The thyroid, as do many of the glands in the body, operate under a feedback mechanism. In other words, when there are low amounts of a particular hormone, the body signals other glands in the chain to release hormones that act upon the gland to release additional hormones. For example, with low levels of thyroid hormones in the blood, a signal is sent to the hypothalamus which sends a signal to the pituitary gland to release TSH, or thyroid stimulating hormone.

Hypothyroidism can result from an inactive pituitary gland which fails to secrete enough TSH. Since this is the hormone that stimulates production of T4 and T3, a low TSH level results in low T4 and T3 levels. There are other reasons for low thyroid hormone levels which can be related to disorders in the hypothalamus or the pituitary gland, or to iodine deficiency, radiation exposure or other conditions.

The treatment of hypothyroidism is dependent on the underlying cause of the condition. Most people are treated with synthetic drugs called levothyroxine sodium, commonly known as Levoxyl or Synthryoid. These medications are synthetic T4. Remember T4 in the body is converted to T3 which actually stimulates the metabolism of the cells. In some cases, lyothyronine sodium, or T3 is used in treatment for underactive thyroid, but since T3 is much shorter acting the dosage must be taken many more times throughout the day.

Treatment of hypothyroidism with T4 involves taking the medication in the morning, thirty minutes before eating. Taking other medications with T4 is not recommended since they can interfere with T4's efficacy. Once drug therapy begins, testing of thyroid levels should be taken every 6 weeks to ensure adequate amounts of hormone in the bloodstream. An excessive amount of hormone can be damaging to the heart, causing palpitations. It can also increase blood pressure, so monitoring thyroid drug treatment is very important.

Once treatment for an underactive thyroid has proven successful and the hormone levels are being maintained, a yearly blood test is adequate for continual monitoring. If symptoms such as weight gain, tiredness, depression, dry skin, muscle cramping or constipation appear, consult your physician as an adjustment in dosage may be needed. Blood levels of T4, T3 and TSH will provide a comprehensive picture of adequacy of the drug therapy.