Thyroid Function

The word “thyroid” is derived from the Greek word meaning “butterfly”, since the gland is shaped somewhat like a butterfly.  The gland itself lies just beneath the skin between the “Adam’s Apple” and the notch separating the collar bones. This small gland controls energy production in the mitochondria in every cell in the body, and is under the control of the hypothalamus and pituitary glands in the brain, and the adrenal glands, which are located on top of the kidneys.

 Thorough evaluation of thyroid function includes serology (that is, blood testing) to check TSH, free T3 (Free tri-iodothyronine), free T4, thyroglobulin, thyroglobulin antibodies, thyroid peroxidase antibodies, and reverse T3, as well as measuring adrenal and pituitary function.  TSH, or thyroid stimulating hormone, is made in the pituitary gland, and is not in itself a true thyroid function test.  In most cases, if the pituitary gland is functioning properly, the TSH will rise when the thyroid hormones are low.  However, we sometimes see hypothyroidism caused by low pituitary function, in which case the TSH will be low, as well as the free T4 and/or free T3 levels.  Therefore, one cannot diagnose thyroid disease by measuring only the TSH level.

There are at least two minerals (heavy metals) that must be present in order for the thyroid to function properly, and these are selenium and iodine.  We measure whole blood selenium, and use a 24-hour urinary collection to assess the body’s iodine stores.  When indicated, we supplement these minerals and monitor levels of them carefully.

Hypothyroidism, or LOW thyroid function, frequently causes brittle hair, hair loss, dry eyes, dry skin, memory loss, cognitive impairment, concentration difficulties such as ADD and ADHD, depression, slow heart rate, fatigue, increased need to sleep (hypersomnia), constipation, muscle aches, generalized weakness, plantar fasciitis (soreness in the soles of the feet) and many other signs and symptoms.  Evaluation of depression always should include a thorough thyroid workup since hypothyroidism is frequently the cause of depression.

 Comprehensive evaluation of the thyroid includes blood testing to quantify antibodies against the thyroid, which are called thyroid peroxidase and thyroglobulin antibodies.  We often note that a person may have these antibodies, in which case we diagnose “Hashimoto Thyroiditis”.  Frequently, the TSH, free T3 and free T4 may be normal in the presence of Hashimoto Disease.

 Hyperthyroidism can also occur, and usually the symptoms are opposite those of hypothyroidism, with the exception of fatigue and weight gain or loss, which can occur in either hypo- or hyperthyroidism.  Hyperthyroidism can be of several types, including a transient viral thyroiditis, as well as Graves Disease.  Graves Disease was so-named after a physician whose surname was Graves.  Graves Disease is the type of hyperthyroidism which can cause the eyes to bulge forward in some people (exophthalmus, or proptosis).

 After the appropriate serology is obtained to determine thyroid function, we might want to image the thyroid to determine whether nodules are present, in which case we order a thyroid ultrasound test. This test is performed at a testing center such as would offer radiographs (X-rays), CT scans, and so forth, and is painless.  Should the scan show nodules, we might then want to evaluate the nodules further to be certain that they are benign.

 Evaluation of thyroid nodules involves an imaging testing known as a nuclear medicine scan.  We also continue to order iodine uptake scans to evaluate thyroid function, particularly if we suspect Graves Disease to be present.  Should we uncover a thyroid nodule suspicious for malignancy, we ask the assistance of a thyroid surgeon, who will perform a needle biopsy of the nodule in her/his office for us under local anesthesia.

 In cases of hypothyroidism, appropriate medications must be chosen and monitored monthly until balance is achieved.  Medications include synthetic preparations of levothyroxine (“T4”) such as Synthroid, Levothroid, Levoxyl, Unithroid, and others.  We never use generic T4, called levothyroxine, however.  For people whose T3 level is low despite administration of T4, there is the synthetic triiodothyronine (“T3”) medication called Cytomel.  Cytomel can be administered concurrently with any of the T4 medications.  Cytomel causes the TSH to fall rather quickly, and must be given with close attention to the levels of the hormone and close monitoring of the physical exam and symptoms, in order to avoid hyperthyroidism.

The traditional medical textbooks clearly state that T3 deficiencies exist, and that certain people may not be able to convert the inactive T4 hormone to T3, which is one of the active thyroid hormones. Yet, many physicians do not acknowledge this fact, and will state that they “don’t believe in T3”.  We are unclear as to how physicians choose “not to believe” the facts. Information is available now that confirms that people can have an abnormality in the enzymes that convert T4 to T3, known as the 5-prime de-iodinase enzyme, and that they will do well with the addition of T3 to the regimen. In addition, we are learning that there may be antibodies to receptors in the body for each of the thyroid hormones.

 One prescription combination medication containing both T3 and T4 is called Thyrolar.  In this preparation, both hormones can be given in a single tablet.  The disadvantage is that both hormones must be changed with every dose change, which is not always desired.

 The oldest prescription medication for hypothyroidism is a porcine glandular product known as Armour Thyroid.  For over a century this medication has existed, and indeed used to be the only medication available to treat low thyroid.  Armour fell out of favor in the past due to quality control issues.  However, quality control now seems to be dependable, in our experience.  Armour thyroid contains all of the components of the thyroid gland, including hormones we are learning more about recently, called T1 and T2.  These hormones seem to be involved in energy production.  The disadvantage of this preparation is that the individual hormonal components cannot be changed.   With Armour thyroid tablets, we often find that people require extra T4, in which case they might be on a Synthroid-like drug in addition to the Armour.

 Some practitioners use bovine thyroid gland preparations.  We have one patient out of our thousands of patients whom is doing well on a bovine (that is, cow) product.

In addition to balancing the thyroid hormone levels, we believe that it is the physician’s responsibility to uncover the CAUSE of any glandular disorder, and that includes both hypothyroidism as well as hyperthyroidism.  The hypothalamic-pituitary-adrenal-thyroid axis is intricate and should be considered a part of the “endocrine web” when treating a thyroid disorder.

In summary, this text is an over-simplified synopsis about thyroid function which we hope you will find useful. By no means is this intended to be a comprehensive delineation of thyroid structure and function.