Top 11 diagnostic tests for hypothyroidism

Hypothyroidism or the ‘under- active thyroid’ is a medical condition wherein the vitally important thyroid gland secrets too little of thyroid hormone. Thyroid hormone is important for body’s metabolism as it acts on almost all body cells, determines body’s sensitivity to catecholamine hormones and also helps in stabilization of body’s temperature. In hypothyroidism, the thyroid gland secretes little hormones. This may be caused due to Graves’ disease, excess iodine, inflammation of thyroid, or non-cancerous or cancerous tumors. This medical condition is diagnosed through use of a variety of tests, particularly invasive tests such as blood test and non invasive procedures such as systolic blood pressure tests. These tests may be used in combination with each other and the patient generally has to make just one visit to the physician for tests and another for discussion of results.

Before a patient undergoes series of testing procedures, the clinician is supposed to note the symptoms. Generally, people with hypothyroidism may experience increased sensitivity to cold, constipation, depression, patches all over skin, paleness, thin or brittle hair, weight gain, joint pain, heavier menstrual periods and puffy face. Observation of symptoms is a non-invasive procedure and generally requires single visit to the physician, but depending upon the symptoms, the patient may have to pay several visits for proper diagnosis and treatment.

Top diagnostic tests

1. Measurement of Serum Thyroid Hormone T4

T4 by radioimmunoassay is a commonly used thyroid testing procedure. The test is also known as T7 and is an upgraded version of T3 test. The test corrects the effect of certain medications such as seizure medication, cardiac drugs and aspirin which can alter the results of thyroid test. The test itself reflects the amount of thyroxine in patient’s blood. The test is of great importance if the patient hasn’t been taking any thyroid related medication before. The test is generally performed along with T3 test and with radioactive iodine uptake for accurate diagnosis. In case of hypothyroidism, T4 levels are low.

2. Measurement of Serum Thyroid hormones through T3

T3 test measures the levels of triidothyronine hormone in the blood. Although thyroxine comprises 80 percent of thyroid hormone, testing tiidothyronine (comprises 20 percent) is important for diagnosing the ailment. This is because in certain cases of hypothyroidism, the gland produces normal levels of T4 but secretes lower quantities of T3. Therefore, T3 and T4 tests are performed together. They both are invasive procedures, require single visit to laboratory as they are performed on same day.

3. Measurement of pituitary production of TSH

IRMA or immunoradiometric assay is the test that measures pituitary production from thyroid stimulating hormone or TSH. There are several cases in which the thyroid may produce normal amounts of T3 and T4 even with hypothyroidism. So, this test may be used to measure pituitary production as the thyroid gland of an individual suffering with hypothyroidism will have a decrease in TSH which will indicate that pituitary gland is unable to increase the circulation of thyroid hormone which has caused hypothyroidism. This test is invasive procedure and it can be performed along with T3 and T4 tests.

4. Thyroid binding globulin

In human blood, the thyroid hormones are attached to thyroid binding globulin, a protein which can alter the measurement of T3 and T4 without affecting the overall action of the hormone. The test is performed if a patient shows abnormal values of T3 and T4 without any explanations. The direct measurement of this hormone can help in preventing misdiagnosis of hypothyroidism wherein the T3 or T4 is altered without any changes in thyroid gland itself. This invasive procedure requires separate visit to the physician as the test is only performed if the values of T3 or T4 are abnormally low. The test can indicate presence of any hereditary disorders that may have caused low secretions of thyroid hormone in the blood or high levels of T3 or T4.

5. Radioactive iodine uptake scan

This test measures thyroid function in terms of how much iodine is taken up by the gland. Generally, the thyroid gland absorbs iodine from blood stream through the foods we eat and then uses this iodine to make thyroid hormone. Patients with hyperthyroid may take excess iodine which results in hyperthyroidism. But patients with hypothyroidism will essentially have lower amounts of iodine and most of it will be excreted through urine. Therefore, in this test, a particular dose of radioactive iodine is given to the patient on an empty stomach. The iodine is then either taken up by thyroid gland or else excreted in urine. The amount of iodine that goes to the thyroid gland is measured as ‘thyroid uptake’. This non-invasive procedure is usually over a period of one day and the patient might have to stay in the hospital overnight. At the same time, the patient may have to take a blood test as the interpretation of this test is done in combination with the results of blood tests. A person undergoing this test must not eat anything 8 hours before the test.

6. Blood tests

These tests are performed to evaluate the blood levels of thyroid hormones. Blood tests are invasive procedures that measure whether the levels of TSH have increased or decreased in the blood. Generally, a patient with hypothyroidism would have increased levels of TSH and decreased levels of T3 and T4. Blood tests may also indicate the cause behind presence of hypothyroidism such as Graves’ disease, non-cancerous growth or cancer (in rare cases).

7. Examination of thyroid antibodies

In pregnant women, the presence of T3 and T4 can be high or low even if they don’t have hypothyroidism. Therefore, for pregnant women, a special examination of thyroid antibodies is conducted to confirm whether the thyroid is underactive or overactive. This examination consists of both non-invasive and invasive testing procedures that are performed over a period of one day. The examination may be performed more than once if the reason behind the symptoms related hypothyroidism is unclear. The test is beneficial for pregnant women since they cannot undergo thyroid scan for diagnosis and treatment of hypothyroidism.

8. Glucose test

Blood glucose test may be performed at the initial stage to know whether the patient needs to go for proper testing to diagnose hypothyroidism. A blood sample is needed to perform this test. Therefore, it is an invasive procedure. Lower than normal levels of blood glucose indicate overactive thyroid gland or hypothyroidism. In such cases, the patient is asked to undergo several other hypothyroidism tests including TSH testing, T3 and T4 testing and iodine scan. Glucose testing can also indicate presence of related disorders such as diabetes or seizures.

9. TRH test

In a healthy individual, the levels of TSH secretion can be easily increased by an injection of TSH releasing hormone of TRH into their bloodstream. But for a patient suffering from hypothyroidism, TSH levels would show a dramatic rise after the shot of TRH. TRH test is therefore, used for detecting early hypothyroidism and even hyperthyroidism. This invasive procedure requires at least one visit to the clinician. Patients who show little or no response of TRH may be suffering from hyperthyroidism while patients should too much response to TRH (above 40) may be diagnosed with hypothyroidism. In several testing laboratories, this test has been combined with the TSH test for faster testing and accurate diagnosis.

10. Thyroid scan

Thyroid scan is a non-invasive procedure that takes an image of thyroid gland to indicate how well it is functioning. To perform this test, the patient is given a radioisotope. The thyroid gland concentrates on the isotope. Earlier the scan used to use isotopes such as technetium, but nowadays, clinicians have started using radioactive iodine. The test also helps in identifying whether the thyroid nodules that are overactive are cancerous (this happens rarely). There are two types of thyroid scans available: camera scan, which is very common and uses gamma camera that provides image of entire thyroid gland at once and the other is Computerized Rectilinear Thyroid scanner which enhances thyroid nodules for better interpretation. The scan barely takes five to ten minutes for completion. Only pregnant women should not get thyroid scans as the iodine used in this scan can cause development issues with baby’s thyroid gland.

11. Physical examination of the patient

A thorough physical examination may be performed for evaluation of symptoms and proper diagnosis. The doctor may look for an enlarged thyroid glands, signs like protruding eyes, presence of rashes, fine tremor in hands, problems like muscle weakness and rapidity of pulse to identify the medical condition. In several cases, the physician may also look for genetic testing or other procedures to find any hereditary issues that can be associated with hypothyroidism. For instance, patients with high levels of T3 and T4 without any apparent problems with thyroid gland may go for hereditary testing to find out the exact cause. Physical examination is also conducted for some rare conditions related to hypothyroidism such as cancer.

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