Thyroid hormone is a metabolic hormone secreted by the thyroid gland that regulates temperature, metabolism and cerebral function. It contributes to energy levels and temperature regulation and body warmth. It increases fat breakdown, resulting in weight loss as well as lower cholesterol. It protects against cardiovascular disease and improves cerebral metabolism. It helps to prevent cognitive and memory impairment. Thyroid hormone is probably the safest and most beneficial cholesterol- lowering agent, yet it is infrequently used for this! More than any other hormone, the thyroid hormone is most responsible for improvement in energy and reducing fatigue.

We often get calls from patients whose primary care physicians have told them their thyroid is too low or too high. Because this is confusing, let us try to give you a better understanding.
The thyroid gland produces a hormone called T4. The number 4 indicates it has 4 iodine molecules. The body produces an enzyme that removes an iodine molecule and converts the T4 hormone into T3, which is the active form of the thyroid hormone. What is free and circulating in the system, available for the body to use, is the Free T3. It is the Free T3 that has the effect on energy, metabolism and all thyroid functions.

The most common thyroid measurement is the TSH or Thyroid Stimulating Hormone, which stimulates the thyroid gland to produce thyroid hormone. This is a gauge that is opposite of your thyroid production. If the body senses there is enough thyroid present, the TSH will be low. Conversely, if the body senses there isn’t enough thyroid, the TSH goes up, trying to stimulate the thyroid gland to make more thyroid. Here is part of the confusion. If you doctor says your thyroid is low, do they mean the TSH is low, which indicates that your actual thyroid is high? Or do they mean that your actual thyroid is low, in which case the TSH would be high?

A second point of confusion, not well understood by your physicians: If your thyroid gland is producing T4 or you are taking thyroid in the form of T4 (most commonly Synthroid® or levothyroxine), the TSH will respond to the presence of T4 and most probably be low or at a number with which your physician is comfortable. However, if the T4 is not converting into T3, the TSH will not reflect this. And if the T4 is not converting into T3, you might have all the symptoms of not having an adequate amount of thyroid since it is the T3 that is the gas in the tank. The only way to assess the Free T3 is to measure it.

Most physicians do not measure Free T3, but only measure TSH. However, as seen above, it is not a full picture of your thyroid function. Most physicians are taught to treat this TSH number and not necessarily listen to how the patient feels (most patients feel better when Free T3 is optimal).

When you supplement with Armour Thyroid or compounded desiccated thyroid, it contains both T4 and T3 in a bio identical form. The T3 gives you the energy early in the cycle while the T4 is converting into T3 for energy mid and late cycle (the cycle is typically about 7-8 hours). If we measure your Free T3 around 4-5 hours after you take your thyroid, we see how well your body is converting the T4 into T3. It is this measurement of Free T3 that is the most reflective of your thyroid levels.

Typically, when your Free T3 is optimal – close to the high end of a normal range – we will see that the TSH will be very low. This is what concerns your physicians. However, if your Free T3 is good and you feel well, without symptoms of too much thyroid (ie: heart palpitations, nervousness), your dose is usually fine, or as we prefer to say, optimal.

However, because this difference of opinion seems to anger some primary care physicians, when your doctors test your TSH and advise you that your thyroid dose needs lowering, and we are advised of this, we will be lowering your thyroid dose to please your physicians. Appeasing them will spare you any confusion, but might result in a return of low thyroid symptoms.

“Fibromyalgia is frequently seen in hypothyroidism. There is now evidence to support that fibromyalgia may be due to thyroid hormone resistance (cellular hypo-function).” Medical Hypotheses 2003 Aug; 21(2): 182-89.

“Combined T4 and T3 therapy resulted in improved symptoms, well-being and weight loss in comparison with straight T4 therapy. A decrease in weight resulted from using higher T3 levels.” J Clin Endocrinol Metab. 2005 May; 90(5):2666-74.

“Long term high doses of thyroid had no adverse effect in causing osteoporosis or fractures” Cortland Forum July 2001:85-90
“TSH is a good test to diagnose hypothyroidism. However TSH is a poor measure of symptoms of metabolic severity. It is, therefore, the biological effects of thyroid hormone on the peripheral tissue and not the TSH concentration, that reflects the clinical and metabolic effects.” British Medical Journal Feb 2003;Vol. 326:325-326.

“Even exceptionally high doses of thyroid do not cause osteoporosis or fractures.” Normal Metabolic. Research 1995 Nov; 27(11): 503-7.

“Even though the TSH is in the normal range, patients continue to have persistent symptoms despite adequate replacement doses. These patients are still symptomatic due to low T3 levels.” BMJ Feb. 2003; Vol. 326:295-296.

“Patients that took a combination of T4 and T3 experienced better mood, energy, concentration and memory and improved well-being. Patients on just T4 experienced no change.” New England Journal of Medicine Feb. 1999; 340:424-9.

“Women with low normal thyroid levels had a 4-fold increase risk of heart disease. This increased risk was equal to the risk of smoking and high cholesterol. Low normal thyroid levels are a strong predictor for heart attacks.” Annals of Internal Medicine, 2000; 132: 270-278.

“Low T3 levels are associated with increased heart disease and decreased cardiac function. Replacing T3 increases clinical performance and cardiac output. Adding T3 increases exercise tolerance and quality of life.” CVR & R 2002; 23:20-26
“Low levels of free T3 in patients resulted in increased disability, depression, decreased cognition, and energy and increased mortality.” JAMA Dec. 2004; Vol. 292(2c): 500-504.

“Low normal thyroid levels result in increased cholesterol, increased heart disease, fatigue, low energy, depression, and memory loss. Thyroid replacement eliminates thee risks. No study has shown any harm or adverse effect of treatment.” Consultant 2000 Dec: 2397-2399.

“Long term thyroid replacement with high doses has no significant effect in bone density or fractures.” Lancet 1992 Jul 4; 340(8810): 9-13.

“Thyroid levels should be raised to the upper normal range for a young person. This results in optimal cognition, memory, cerebral function.” Journal of Gerontology; 1999 Vol. 54:109-115.

“Combined thyroid therapy with T4 and high dose T3 resulted in improvement of symptoms and well being, whereas straight T4 did not. Not only did they feel better, but the patients taking both T4 and T3 also lost weight. The straight T4 did not.” Journal of Clinical Endocrine Metabolism 2005 May; 90(5): 2666-74

“Over 40 studies prove that thyroid replacement does not lower bone density or cause increase risk of fracture.” Cortland Forum; 2001 July: 85-89.

“Decreased T3 levels result in increased cholesterol and heart disease. Treating with T3 improves the lipid profile.” Preventive Cardiology, 2001; 4:179-182