Table of Contents
Diagnosis
Doctors diagnose hypothyroidism after completing a medical history and physical exam of the patient and performing laboratory tests on the patient's blood. Because symptoms of hypothyroidism can mimic those of many other conditions, blood tests for measuring levels of thyroid stimulating hormone (TSH) and free thyroxine (T4) are the only definitive way to diagnose hypothyroidism. However, the results of these blood tests can be affected by illnesses that are not thyroid related.
Physical Examination
The doctor will check the heart, eyes, hair, skin, and reflexes for signs of hypothyroidism.
Goiter. The presence of a goiter (an enlarged thyroid), especially a rubbery, painless one, may be an indication of Hashimoto's disease. If the thyroid is tender and enlarged but not necessarily symmetrical, the doctor may suspect subacute thyroiditis. A diffusely enlarged gland may occur in hereditary hypothyroidism, in postpartum patients, or from use of iodine or lithium. Goiters may also develop in people with iodine deficiency.
Thyroid Hormone and Antibody Tests
In diagnosing hypothyroidism, blood tests measuring thyroid hormone levels are needed to make a correct diagnosis. In some cases, antibody tests are also helpful.
Thyroxine (T4). Hypothyroidism is a condition marked by low thyroxine (T4) hormone levels, and a test can measure levels of this hormone in the blood. However, this test is usually inadequate for the following reasons:
- T4 levels can be normal early in the disease process leading to hypothyroidism. If hypothyroidism is suspected, other tests are needed.
- T4 levels can be low in patients who do not have hypothyroidism. For instance, thyroxine can be extremely variable in very elderly or seriously ill patients and during pregnancy.
Previous Section
Review Date: 05/03/2011
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine,
Harvard Medical School; Physician, Massachusetts General Hospital.
Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M.,
Inc.
A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)
