As I have discussed in other thyroid articles, diagnosing an underactive thyroid (Hypothyroidism) involves a comprehensive review of a patient’s medical history, symptoms, and tests results. Once the diagnosis is made or suspected, treatment can be initiated. However, a complete understanding of thyroid function is necessary to implement effective treatment. So, before I discuss treatment options, I would like to review the basics of thyroid physiology.
The thyroid gland produces several types of hormones that influence almost every cell in the body. In general, hormones are chemicals produced by our body to regulate and an infinite number of activities. Cells throughout our body contain specific receptors for particular hormones, and hormones fit into their associated receptors like a key fits into the ignition of a car. Not unlike the ignition key of a car, when a hormone activates its receptor, it initiates a designated process or function. This is the mechanism by which thyroid hormones work to regulate our metabolism, influence energy production, and perform countless other tasks.
The primary thyroid hormones that we consider clinically are Thyroid Stimulating Hormone (TSH), T4, and T3. The brain releases (TSH), which triggers the thyroid gland to release its hormones, T4 and T3. The thyroid gland produces about 10 times more T4 than T3, yet T3 is much more biologically active than T4, which is a little counterintuitive. Most thyroid receptors respond to T3 and not T4, so you would expect the thyroid gland to focus on T3 production instead of T4. Although, the thyroid gland produces mostly T4, much of this gets converted to T3 as it floats around the body…or at least it should get converted. This doesn’t always happen as expected and here lies some of the confusion associated with thyroid treatment.
Generally, when the thyroid gland is underactive and not producing enough T4, the brain increases TSH production to stimulate more thyroid activity. Many physicians only check TSH levels to evaluate thyroid function. If the TSH is high, then the thyroid is considered to be underactive. If it is normal, then everything is OK. This is how most of us were taught in medical school to evaluate the thyroid gland. Unfortunately, this approach may miss some critical aspects of thyroid function. As I stated, T3 is the most active thyroid hormone. I often see patients with hypothyroid symptoms and blood test showing normal TSH levels and normal T4 levels. The patient feels lousy, but their doctor only checked their TSH level and maybe their T4 level and told them that their thyroid is not the problem. Often the thyroid gland is producing enough T4, but it is not being adequately converted to T3. The patient’s T3 levels are low and they are not getting enough of the hormone to carry out all of the important thyroid functions. I’m not sure why so many doctors are reluctant to test a full thyroid panel, including T3 levels, but I see this scenario often.
Other problems can also present. T4 can be converted into Reverse T3, which is another form of thyroid hormone that has no thyroid activity and will actually inhibit the activity of T3. Again, I seldom see Reverse T3 levels checked, but it is an important aspect of thyroid function. If Reverse T3 levels are high, it needs to be addressed. Patients may also have thyroid receptors that do not function well, which often occurs when there is poor balance between estrogen and progesterone. In these cases, the patient may have enough T3 available, but the hormone cannot complete its tasks because it cannot activate poorly functioning thyroid receptors. All of these issues can lead to symptoms of an under active thyroid and may go undiagnosed unless T3, Reverse T3, and sex hormone levels are checked along with TSH and T4 levels.
A comprehensive evaluation is also necessary to help direct effective treatment. Most conventional treatment revolves around the common medications, Synthroid or Levothyroxine. These are essentially T4 hormones. If a patient has a high TSH or low T4, most doctors prescribe a T4 medication to boost T4 levels. This will help lower the TSH back to normal and increase T4 levels, but it may not help the patient with their symptoms. As stated previously, T3 activity is the key. If a patient has difficulty converting T4 to T3, they may not benefit from receiving more T4. Although some patients do well on these medications, not all do. I often see patients who had their TSH and T4 levels improve after starting Synthroid, but they don’t feel much better. If a patient is doing well, I leave them on their current medications. If they aren’t, I will do further testing as I mentioned above.
I will first look at their T3 level. If it is low, I consider adding T3 hormone to their regimen with Liothyronine (a T3 medication) or a natural T4/T3 thyroid preparation, such as Armour Thyroid. I could also have a customized combination preparation compounded to meet a patient’s specific needs. In addition to this, there are other factors that influence the conversion of T4 to T3. Adequate levels of certain Vitamins (A, E, and D) and optimal cortisol levels are needed to facilitate T4 conversion to T3. Also, Selenium is needed for this conversion and also to prevent the production of too much Reverse T3. If I find high Reverse T3 levels, I suspect my patient has a selenium deficiency and prescribe a selenium supplement. As always, I listen to the patient when implementing treatment. Tests are important to ensure that therapy is managed safely, but they are not the only guide for therapy. Making numbers look better doesn’t always mean the patient feels better. Medication may be adjusted based on patient symptoms, or if they do not respond to thyroid therapy, other causes for their symptoms may have to be investigated.