In the United States, about 5 percent of the population has hypothyroidism, or an underactive thyroid, according to the National Endocrine and Metabolic Diseases Information Service. An underactive thyroid does not produce the normal level of hormones, which affects metabolism.
To diagnose an underactive thyroid, a physician will use several tests. The National Endocrine and Metabolic Disease Information Service noted that the thyroid-stimulating hormone, or TSH, test is usually the first test used, and is also the most accurate test of the thyroid’s activity.
Patients with an underactive thyroid will have an elevated level of TSH, as the pituitary gland makes more TSH when thyroid hormones are low. The physician may also use a T4 test and a thyroid autoantibody test to diagnose an underactive thyroid.
A T4 test checks how much T4 is circulating in the patient’s blood. A patient with hypothyroidism will have lower than normal levels of T4. The thyroid autoantibody tests looks for thyroid autoantibodies, which are present in patients with Hashimoto’s disease.
Once the physician has diagnosed the patient with hypothyroidism, the next step is to choose the proper treatment. For example, if a patient has overt hypothyroidism, in which she has TSH levels of 10 mU/L or above and lower T4 levels, she will undergo thyroid replacement therapy, according to the University of Maryland Medical Center.
The patient is given synthetic thyroxine — which is identical to T4 — though how much she takes depends on how severe the hypothyroidism is, as well as other medications she is taking, her age, weight and other present health conditions.
Once the patient starts taking synthetic thyroxine, her physician will check her TSH levels every six to eight weeks. After the dose is stable, the physician will check her TSH levels every six months then once a year, noted the National Endocrine and Metabolic Diseases Information Service.
Finding the right dose of synthetic thyroxine is important, as an excessive dose can cause side effects. A patient taking too much synthetic thyroxine can have shakiness and insomnia. Heart palpitations and an increased appetite may also occur. Certain foods and medications may affect absorption of the synthetic thyroxine.
The MayoClinic.com noted that large amounts of soy products, high-fiber diets, calcium supplements, iron supplements, aluminum hydroxide and cholestyramine may interfere in absorption.
The University of Maryland Medical Center pointed out that there is a debate over the treatment of subclinical hypothyroidism, in which the patient does not have obvious symptoms, her T4 levels are normal, and her TSH levels are only slightly higher than normal. Some physicians suggest monitoring patients while other prescribe treatment.
Treatment of hypothyroidism may vary for certain cases. For example, if a patient has both hypothyroidism and an iodine deficiency, her treatment may consist of iodized salt, according to the University of Maryland Medical Center. A patient who has heart disease will start with a very low dose of synthetic thyroxine, as the treatment may cause chest pain or a heart attack.
References
National Endocrine and Metabolic Diseases Information Service. Hypothyrodism. Web. 4 January 2012
http://endocrine.niddk.nih.gov/pubs/Hypothyroidism
MayoClinic.com. Hypothyroidism: Treatments and Drugs. Web. 4 January 2012
http://www.mayoclinic.com/health/hypothyroidism/DS00353/DSECTION=treatments-and-drugs
University of Maryland Medical Center. Hypothyroidism – Treatment. Web. 4 January 2012
http://www.umm.edu/patiented/articles/how_hypothyroidism_treated_000038_7.htm
Reviewed January 4, 2012
by Michele Blacksberg RN
Edited by Jody Smith