The thyroid is a small gland located in the front of the neck below the voice box. When underactive, the gland produces too little thyroid hormone to maintain a proper energy level in the body. A simple test is used to detect underactive thyroid, with other evaluations performed to confirm the diagnosis and find the underlying cause, reports MayoClinic.com.
Considerations
Underactive thyroid is more common than people realize, with incidence increasing with age, especially in women, reports EndocrineWeb.com. Because many symptoms are nonspecific or painless, people may not know they have this condition, reports MayoClnic.com. As the disease progresses, the signs become more pronounced.
Screening
A simple and inexpensive blood test for TSH, thyroid-stimulating hormone, is the best screening tool for underactive thyroid. This sensitive test is able to detect improper levels of TSH early, even before people have symptoms, reports MayoClinic.com. People with generalized signs---such as fatigue or weight gain despite no change in their ordinary activities--should take this test. In fact, it is recommended every two years for all people over age 55 years, reports The Merck Manuals.
Diagnosing Hashimoto's Disease
Doctors perform further tests find out why the thyroid is underactive, reports MayoClinic.com. The most common cause in the United States is Hashimoto's disease, an autoimmune system disorder that attacks the thyroid and creates high levels of abnormal antibodies. A blood test for antibodies against TPO, thyroid peroxidase, an enzyme that normally creates thyroid hormones, confirms the presence of Hashimoto's disease.
Other Evaluations
If doctors suspect the pituitary gland has a problem, which is rare, they may perform additional tests to detect hormone levels in the thyroid and the pituitary, which directs the thyroid to produce chemicals, explains EndocrineWeb.com and the Merck Manuals. Both T4, thyroxine, the main thyroid hormone, and T3, triiodothyronine, an active hormone created by T4 that regulates metabolism, are assessed.
Management
Once medicine is prescribed, typically levothyroxine, a synthetic thyroid hormone, doctors perform TSH tests every few weeks to ensure the patient is getting the right dosage. If there is too much TSH, they reduce the dose of levothyroxine. This is important because, over time, excessive TSH can worsen osteoporosis and make the heart beat too fast, explains MayoClinic.com.
