Test Thyroid Function

Some people feel much better when taking thyroid hormones, even though some thyroid tests might indicate that they do not need it.

For sub-clinical cases, a short-term thyroid trial is appropriate. The best lab tests to consider if low thyroid function is suspected are TSH (Thyroid Stimulating Hormone), Free T-4, and Free T-3. Your doctor may or may not require lab testing before giving you thyroid hormone on a clinical trial basis, when symptoms indicate. If your doctor refuses to give you a clinical trial and does not provide a convincing reason, you may wish to get a second opinion.

Oral temperatures during the day are a reasonable method of monitoring your thyroid status and the effectiveness of any thyroid medication. Since the thyroid regulates the body’s metabolic rate, greater thyroid activity usually results in a higher body temperature. Your body temperature should be greater than 98.2F (36.8C).

The American Association of Clinical Endocrinologists officially stated in 2001, that a “TSH level between 3.0 and 5.0 uU/ml … should be considered suspect since it may signal a case of evolving thyroid underactivity.” This is a dramatic reversal, as they have traditionally held that patients should never be treated with thyroid hormone unless the tests were clearly abnormal, above 5.5. This supports the belief that many patients have been misdiagnosed and undertreated in the past based on the lab tests and the arbitrary normal ranges. Testing should also be done when hyperthyroidism is suspected. A low TSH is suggestive, but if borderline, a free T-3 can be done.

Thyroid lab testing can be done while you are on your thyroid medication. Some doctors recommend taking your daily thyroid dose after any thyroid lab testing is done, not before.

Free T3 testing may be needed to determine if hypothyroidism (or hyperthyroidism) is an issue and if it is being effectively treated. T4 is converted to T3 in the body, and T3 is much more metabolically active than T4. In normal thyroid function, as the concentrations of the carrier proteins change, the total triiodothyronine (T3) level also changes, leaving the free T3 concentration relatively the same (In an abnormally functioning thyroid, this is not necessarily so). Measurements of free T3 concentrations, therefore, correlate more reliably with your clinical status than either total T3 or T4 levels. For those who are taking T4 as their only thyroid medication, it is sometimes helpful to determine what their free T3 level is, to make sure that good conversion of T4 to T3 is taking place.

In cases where the TSH is elevated but hypothyroid symptoms are not present, thyroid enlargement or tenderness suggests autoimmunity. Antithyroid antibodies such as antithyroglobulin and antiperoxidase may be atacking the thyroid gland. These autoantibodies can be found on blood testing. If the TSH is as high as 10 or so, but there are no autoantibodies or symptoms, some doctors will not treat, but watch the condition to see if there is any progression.


Test Thyroid Function can help with the following



Chronic Thyroiditis

If antithyroid antibody testing has not yet taken place, and chronic thyroiditis is suspected, your concern should be expressed at your next clinic / doctor visit.

Antimicrosomal (anti-M) and antithyroglobulin (anti-Tg) antibodies are commonly measured together to detect Hashimoto’s thyroiditis. Since this nearly doubles the cost of testing for one antibody, we wished to determine whether significant diagnostic loss would occur if the two tests were replaced by anti-M alone. Both tests were performed in 2030 consecutive patients referred by general internists and endocrinologists.

With a positive result defined as either test being positive at a 1:100 dilution, anti-M was much more sensitive than anti-Tg. Anti-M was positive in 99% (823/831) of all patients with positive tests, while anti-Tg was positive in 36% (302/831). Anti-M was the only positive test in 64% of all patients with positive tests, while anti-Tg was the only positive test in 1%. With a cutoff point of 1:400 dilution, the results were similar.

CONCLUSIONS: Anti-M alone appears sufficient to detect autoimmune thyroid disease at about one half the cost of routinely performing both anti-M and anti-Tg studies. The widespread practice of performing both tests increases the cost without an offsetting diagnostic gain. [The superiority of antimicrosomal over antithyroglobulin antibodies for detecting Hashimoto’s thyroiditis, Nordyke RA, Gilbert FI Jr, Miyamoto LA, Fleury KA. Straub Clinic and Hospital, Honolulu, Hawaii.]



Atrial fibrillation is 3 times more likely in an elderly person with low TSH. [Family Practice News Mar 15, 1995]


The Immune System  



Chronic tendonitis is occasionally associated with hypothyroidism.



Panic Attacks

Hashimoto’s autoimmune thyroiditis has been associated with a range of anxiety symptoms including panic attack.




Hypothyroid patients with eczema respond well to thyroid medication.



The presence of hives is sometimes linked to elevated thyroid antibodies. You can be tested for the presence of these autoantibodies.



Menorrhagia (Heavy Periods)

The association of hypothyroidism with menstrual disturbances is well known. However, even minimal thyroid dysfunction may be responsible for menorrhagia and other menstrual disturbances.


May do some good
Likely to help
Highly recommended



Thyroid Gland: An organ with many veins. It is at the front of the neck. It is essential to normal body growth in infancy and childhood. It releases thyroid hormones - iodine-containing compounds that increase the rate of metabolism, affect body temperature, regulate protein, fat, and carbohydrate catabolism in all cells. They keep up growth hormone release, skeletal maturation, and heart rate, force, and output. They promote central nervous system growth, stimulate the making of many enzymes, and are necessary for muscle tone and vigor.


Chemical substances secreted by a variety of body organs that are carried by the bloodstream and usually influence cells some distance from the source of production. Hormones signal certain enzymes to perform their functions and, in this way, regulate such body functions as blood sugar levels, insulin levels, the menstrual cycle, and growth. These can be prescription, over-the-counter, synthetic or natural agents. Examples include adrenal hormones such as corticosteroids and aldosterone; glucagon, growth hormone, insulin, testosterone, estrogens, progestins, progesterone, DHEA, melatonin, and thyroid hormones such as thyroxine and calcitonin.


The chemical processes of living cells in which energy is produced in order to replace and repair tissues and maintain a healthy body. Responsible for the production of energy, biosynthesis of important substances, and degradation of various compounds.


An abnormal condition of the thyroid gland resulting in excessive secretion of thyroid hormones characterized by an increased metabolism and weight loss.


Diminished production of thyroid hormone, leading to low metabolic rate, tendency to gain weight, and sleepiness.


Thyroxin, thyroid hormone also prepared synthetically, for treatment of hypothyroidism and myxedema.


Compounds composed of hydrogen, oxygen, and nitrogen present in the body and in foods that form complex combinations of amino acids. Protein is essential for life and is used for growth and repair. Foods that supply the body with protein include animal products, grains, legumes, and vegetables. Proteins from animal sources contain the essential amino acids. Proteins are changed to amino acids in the body.


A type of serum protein (globulin) synthesized by white blood cells of the lymphoid type in response to an antigenic (foreign substance) stimulus. Antibodies are complex substances formed to neutralize or destroy these antigens in the blood. Antibody activity normally fights infection but can be damaging in allergies and a group of diseases that are called autoimmune diseases.

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