DescriptionAn in-depth report on the causes, diagnosis, treatment, and prevention of hypothyroidism.
Alternative NamesAutoimmune Thyroiditis; Hashimoto's Thyroiditis
Advances in diagnostic methods now make it possible to detect hypothyroidism in almost all cases before severe symptoms develop. Physicians can make the diagnosis of hypothyroidism after completing a history and physical exam of the patient and performing sensitive laboratory tests on the patients blood.
The physician 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 Hashimotos disease. If the thyroid is tender and enlarged but not necessarily symmetrical, the physician may suspect subacute thyroiditis. A diffusely enlarged gland may occur in hereditary hypothyroidism, in postpartum patients, or from use of iodides or lithium. Goiters may also develop in people with iodide deficiency.
Thyroid Neck Check. Women who are experiencing menopausal symptoms which may be masking those of hypothyroidism should perform a simple self-examination called the Thyroid Neck Check.
Thyroid Hormone and Antibody Tests
In diagnosing hypothyroidism, blood tests measuring hormone level 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 they are usually measured. However, the findings from this test are usually inadequate for the following reasons:
Measuring thyroxine is usually performed using a process called a T3 resin uptake to correct for the presence of medications (e.g., birth control pills, aspirin, and others) that could distort the results. Other tests are needed to confirm a diagnosis of hypothyroidism.
Thyrotropin (Thyroid-Stimulating Hormone or TSH). Measuring TSH is the most sensitive indicator of hypothyroidism. (As with thyroxine levels, however, TSH levels can vary in pregnant women and patients who are ill with other conditions.) In general, results indicate the following:
Antithyroid Antibodies. If TSH levels suggest hypothyroidism or subclinical hypothyroidism, then physician will usually perform a blood test for specific antithyroid antibodies that act against a factor called thyroperoxidase. Tests may also be performed for antibodies to thyroglobulin. Results depend on the patient's condition:
Of note, about 10% of the American population and 25% of women over 60 years old carry these antibodies and the majority of these women have no thyroid problems. Only about 0.5% have full-blown hypothyroidism and 10% have subclinical hypothyroidism. In one 10-year study, however, people with normal thyroid results and high levels of antibodies still had an annual risk of 2% to 4% for developing hypothyroidism.
Other Hormone Tests Used for Thyroid Function. Other hormone tests are often taken if hyperthyroidism is suspected. They include tests for triiodothyronine (T3) and thyroglobulin (also called thyroid binding globulin). Such measurements, however, may also be helpful in detecting sudden temporary increases in thyroid hormone (thyrotoxicosis) that can precede certain forms of autoimmune thyroiditis.
Thyroid Scintigraphy. Thyroid scintigraphy tests scan the thyroid and pick up images highlighted by small amounts of radioactive substances. Thyroid scans can be used to determine whether the thyroid is producing normal amounts of hormone. The patient drinks a small amount of radioactive iodine or technetium and waits until it has been through the thyroid. Images of a properly functioning thyroid would show uniform levels of absorption throughout the gland. Overactive areas would show up white and underactive areas would appear dark. Thyroid scans are usually unnecessary unless the physician needs to rule out suspected cancer.
Ultrasound. Ultrasound has limited value, but it can visualize the thyroid and specific abnormalities, such as nodules. (It cannot measure the thyroid glands function, however.)
More Advanced Imaging Tests. If laboratory tests suggest that a pituitary or hypothalamus problem is causing hypothyroidism, the physician will usually order brain imaging procedures using computed tomography (CT) scans or magnetic resonance imaging (MRI). MRIs may also be used for determining the extent of thyroid cancers and of goiters. MRIs are also being used for investigating hypothyroidism in infants and for determining widespread effects of autoimmune thyroiditis (such as Hashimoto's hypothyroidism).
Needle Aspiration Biopsy
Needle aspiration biopsy is used to obtain thyroid cells for microscopic evaluation. It may be useful to rule out thyroid cancer in patients with suspected Hashimotos hypothyroidism, especially if they have difficulty swallowing or develop a goiter. Much like drawing blood, the physician injects a small needle into the thyroid gland and draws cells from the gland into a syringe. The cells are put onto a slide, stained, and examined under a microscope.
Other Blood Tests
Cholesterol levels need to be checked. Other blood tests may be performed to detect levels of calcitonin, calcium, prolactin, and thyroglobulin and to check for anemia and liver function, all of which may be affected by hypothyroidism.
Ruling Out Other Disorders
The symptoms of hypothyroidism are so similar to common conditions, including just aging, it often makes diagnosis difficult.
Conditions That Cause Thyroid Abnormalities. Some conditions may cause thyroid abnormalities without symptoms and must be differentiated from subclinical hypothyroidism. They include, although are not limited to, the following:
Aging-Related Disorders. Some symptoms of hypothyroidism and aging are very similar. Menopausal symptoms often resemble hypothyroidism. Many other problems related to aging, such as vitamin deficiencies, Parkinsons and Alzheimers diseases, and arthritis, also have characteristics that can mimic hypothyroidism.
Obesity. Many people who are overweight believe that they have an underactive thyroid gland, but only a very small percentage of obese people actually have hypothyroidism. Hypothyroid patients generally show only a moderate weight increase of five to 10 pounds, mainly from accumulation of fluid, and in fact they often have a decreased appetite.
Depression. A lack of interest in personal relationships, drowsiness, an increase in sleep, slowing of speech, and general apathy are signs of clinical depression as well as hypothyroidism. The two disorders, in fact, often coexist, particularly in older women, so diagnosing one does not rule out the presence of the other.
Diseases of Muscles and Joints. Joint and muscle aches may be the first symptoms of hypothyroidism. Most likely, however, such pain is not caused by hypothyroidism if other thyroid symptoms remain absent. Numerous conditions can cause muscle and joint pain, and if thyroid levels are normal the physician should look for other causes.