Thyroid Hormones and Disorders
Thyroid hormones are essential to metabolism and to life. They affect the function of every cell of the body. They can also affect the actions of other hormones, and even talk to your genes. Active thyroid hormone regulates the rate of metabolism. It interacts with the actual DNA of the cell and directs many of it's functions.
About Thyroid Hormones
There are two major hormones secreted from the thyroid gland – thyroxine (T4) and triiodothyronine(T3). T4 is only produced by the thyroid gland. T4 is converted to T3, a more potent hormone. Most of this conversion takes place in the tissues rather than in the thyroid gland.
Thyroid secretion is affected by a sensitive feed-back mechanism. Thyroid Releasing Hormone (TRH) is produced by the brain. This hormone then triggers Thryoid Stimulating Hormone (TSH), which does what its name implies. It stimulates the thyroid gland to produce T4. T4 and T3 both stimulate a decrease in the brain releasing hormones as they rise.
Determining the TSH level is the usual way of monitoring thyroid function. TSH also measures the effectiveness of thyroid hormone replacement therapy when medication is used.
Thyroid Disorders
Thyroid disorders are common. A low-functioning thyroid is most common. It occurs more frequently in women, and the incidence increases with age.
Low thyroid function - called hypothyroidism - can cause fatigue, weight gain, depression, high cholesterol, constipation, dry hair and skin, and many other changes. Over time, it can lead to heart disease, and if severe can cause dementia.
High thyroid output – called hyperthyroidism – can also cause severe fatigue as well as significant cardiac problems. Diarrhea, tremors, a rapid heart beat, and sometimes weight loss can occur. Psychological symptoms can also occur.
If you have symptoms of either hypothyroidism or hyperthyroidism, see your doctor right away for a simple blood test that can evaluate your thyroid function.
Hypothyroidism can occur for many reasons. However, the most common one is called Hashimoto’s thyroiditis. This is an autoimmune disorder. Antibodies to some of the thyroid proteins interfere with the function of the gland.
Thyroid dysfunction can frequently be a cause of weight gain or interfere with attempts at weight loss. If you are overweight, you should undergo thyroid function testing. This involves a simple blood draw and can be performed quickly at almost any medical laboratory. These tests must be ordered by your doctor.
If thyroid function is low, you will need to take thyroid hormone replacement, probably for the rest of your life. Most doctors prescribe T4 only (Synthroid, Levoxyl, Levothyroxine) although some may add T3 (Cytomel). These are all synthetic hormones.
A natural preparation of Armour thyroid (from pig thyroid gland) contains both T4 and T3.
Some believe that supplementing with T4 is not sufficient. It may be that T4 is plentiful but that the conversion to T3 is not taking place effectively. T3 supplementation is sometimes helpful if symptoms of hypothyroidism remain after T4 replacement.
Taking thyroid hormone in excess doses in order to lose weight can cause harmful side effects. When thyroid hormones are elevated, toxicity to the heart can occur. A rapid heart beat or other rhythm disturbances may result, and these can lead to heart failure. Bone density also is affected, and taking too much thyroid medication can lead to osteoporosis.
If you are on any thyroid hormone medication, you should have your thyroid hormones measured at least yearly. If you have changed your dose recently, or are symptomatic, then lab tests will be needed more frequently. Be sure you follow up with your physician regularly.
It is important to point out that if your thyroid function is out of balance, it is important to get this working smoothly before you consider any weight loss medications or surgery. You may find out that you will be able to lose the weight safely and naturally, without resorting to drugs or surgery.
For more information about hypothyroidism and thyroid hormone replacement, check out What Your Doctor May Not Tell You About Hypothyroidism: A Simple Plan for Extraordinary Results by Ken Blanchard M.D., Ph. D.