Thyroid hormone function modulates our metabolism, and is a critical part of our body’s ability to adapt to different environments. Its proper fucntion, and medical management, is essential to all aspects of health. When food is plentiful and stress is low, we can run our engines a bit hotter. We have more calories; there’s more energy to burn.
Historically, the human condition has demanded this ability to simply survive. Our existence on the planet has been characterized less by 24-hour restaurants, where we are able find a meal at any hour of the day, and more by periods of feast and famine. As hunter-gatherers, we were never fully assured of where or when our next meal would arrive.
The agricultural revolution transformed life as we know it. A worldwide transition to wheat and corn as staples allowed for year-round caloric intake. Communities and cultures changed with this transition. And so too did our relationship with our thyroid hormone.
Thyroid Hormone Effects: Living in the Modern World
The point of this introduction is a reminder that our thyroid’s functioning has to be evaluated outside of the “natural“ world influences. The ability to move into a low thyroid, or hypothyroid state, was necessary for our survival. In times of stress or starvation, we lowered our metabolism. We traded a state of dry skin, low energy, dry hair, brittle nails, constipation, and absent libido for simple survival.
Lower metabolism meant the potential for a longer life. We could hunker down feeling miserable until the birds and the berries returned. The ability to assume a state of hypothyroidism gave us a second chance.
It has been said that every cell in the body is equipped with a receptor for thyroid hormone. This may be the reason that a hypothyroid state is associated with such a broad array of symptoms.
TSH: Is This the Best Thyroid Test?
For various reasons, the thyroid gland can begin to hypofunction and reduce the amount of thyroid hormone produced. This results either from damage to the gland itself, as is seen in Hashimoto’s Thyroiditis (an autoimmune condition) or from altered messages from the brain to the thyroid gland. To understand how to optimally manage thyroid function, let’s review a short tutorial of thyroid hormone signaling.
Many readers of this blog may be familiar with the lab test TSH. This stands for Thyroid Stimulating Hormone. It is a signaling hormone released from the brain into the blood stream. As the brain “perceives” a need for more thyroid hormone, TSH is released from the pituitary gland. As more TSH is released, the thyroid gland is expected to produce more of the thyroid hormone.
In theory, this relationship is pretty simple. If the thyroid gland is under-producing the hormone, the TSH would be expected to be elevated. Conversely, high thyroid output would be reflected in a low TSH, mirroring the brain’s needs. A simple diagram of the relationship is outlined below.
The diagram above represents the simple, anticipated “teeter-totter” relationship between TSH and thyroid hormone.
You’ll notice I’ve added another factor. Thyroid hormone is in fact two hormones, T3 and T4. More T4 is produced in the gland relative to T3. But while similarly shaped, these two molecules have different functions.
Why TSH May not Accurately Reflect your Thyroid Function
T4 is effectively a pro-hormone, which means that it needs to be converted by the target tissues to T3, the active form. And while the T4 lacks any “punch” at the cells—meaning that it basically itself has no ability to activate them—it is able to suppress the brain’s production of TSH.
Conceivably, one’s thyroid could be producing ample, inactive T4, all the while telling the brain to produce less TSH. But what if the T4 isn’t being properly converted to T3 in the cells? In this case a person is left in a functionally low thyroid state, but with a normal TSH. Recall, the TSH goes up when our thyroid function is down.In short, TSH approximates thyroid function, but doesn’t give all of the information needed to understand the amount of active thyroid hormone in the body. To truly understand these relationships, we need to measure all of the components; TSH, Free T3 and Free T4.
As a physician who has specialized in hormone management for decade, I have had opportunities to examine patients and their symptoms in light of their thyroid health. And I can say that accurate measurement—and management with replacement hormones—is critical. As the expression goes, there are many ways to “skin a cat.” This blog serves to present some of these practices.
Steps to Optimize Your Thyroid Hormone Function
Step 1: Be sure that you measure the correct hormones. Many “bargain basement” thyroid panels measure TSH, and indirect measures of T3 and T4 with tests like “total” T4, or T3 RUI. These combo tests are inexpensive for hospitals and clinics but give sub-adequate information for accurate diagnosis and management.
The correct lab studies provide valuable information. These show us the amount of active thyroid hormone present at the tissue level. I recommend checking TSH (as a general guide), and Free T3 and T4. Thyroid hormone travels in the blood bound to carrier molecules. The free measurements show what’s available to the cells; it doesn’t include the hormone trapped by a carrier protein.
Step 2: Follow the lab tests and the patient. A professor of mine once told me that “your patient is her own biomarker.” This means that often a set of simple questions will tell us how well we are doing with therapy. If she is anxious, jittery, and is having palpitations on her meds, chances are her dosing is off. Her biomarkers are telling you that she is hyperthyroid.
If she’s describing fatigue, constipation, dry hair and skin, and foggy thinking, she is saying—loudly– that she needs more thyroid hormone. She is clinically hypothyroid. The bottom line is that it is important to correlate how a person feels with her correctly obtained lab studies and some easy at-home metrics, which are below.
Step 3: Get more data! Many physicians are fearful of being more, shall we say, proactive with thyroid hormone replacement. They are worried about causing cardiac arrythmias. This is a fancy way of saying an abnormally fast heart rate.
Indeed, a person who is truly hyperthyroid is at risk for cardiac conditions. But this is typically only seen in thyroid disease states, like Grave’s Disease. It is rarely seen with thyroid replacement in healthy individuals without underlying heart disease.
I ask that all of my patients follow daily basal body temperature measurements and take their pulse. They record this—in addition to haw they feel—and report it to me. Wearables like the Apple watch and Fitbit make this easy. And with Covid, we all have a thermometer in the house.
Thyroid replacement is going well when symptoms go away, morning body temperature moves closer to the 36.5-37-degree range, and the heart rate doesn’t go up. This is simple, effective, and inexpensive data to incorporate into thyroid management.
Step 4: Set Goals. Having managed hundreds if not a thousand thyroid patients, I have found that many people feel the best when their free T4 level is around the 50% of the lab’s range. The real magic starts to happen when we drive the Free T3 into the 50-80% range. It is here that people’s biology really begins to click. People feel, look, move, and generally perform better.
The TSH range needs to be considered as well. The normal laboratory range for TSH is generally .5—5.0. Recall that a higher TSH reflects lowered thyroid function in the body. These ranges haven’t been reformatted for decades and are antiquated. My experience shows that anyone with a TSH greater than 2.5, particularly if they have symptoms, will likely benefit with thyroid supplementation.
A good rule of thumb is this. When the TSH is in the .5-1.5 range, people generally feel great—particularly when their Free T3 is in the upper third of the range. For most people, this is the Goldilocks “sweet spot.”
Thyroid Hormone Replacement Strategies: T4
There are basically three tools to replace thyroid hormone at a physician’s disposal. Options include, in descending order of general use, T4 (levothyroxine or Synthroid), T4 plus T3 (desiccated thyroid products like Armour) and straight T3 (liothyronine, Cytomel). Each has advantages and drawbacks.
T4, commonly known as Synthroid, contains none of the active thyroid hormone T3. This means that for the product to work, the conversion from T4 to T3 needs to take place in the user’s body. But commonly only TSH is measured, and a well-intended doc doesn’t know when this conversion isn’t happening. This scenario is probably the most common one I have seen in my practice.
In this case, a patient could be clinically screaming “I need more active thyroid hormone” with the symptoms noted above. But the TSH is in the relative “normal” range, and they are dismissed by their doctor.
T4 also has a long “half-life,” meaning that half of a dose is still in your circulation after 7 days. This is great for the person who occasionally forgets to take the medication; they won’t notice the missed dose. Plenty of hormone remains in the body, and for a while.
Synthroid is the least expensive of the possible formulations, and the easiest to manage when it works. I have seen patients on the same dose for years, with optimized levels of the free hormones that are remarkably stable over this time. However, the majority of patients in my practice had “normal” T4 on levothyroxine, with sub adequate T3.
Thyroid Hormone Replacement Strategies: T3 and T4 Combinations
Several products exist that combine T3 and T4. This combination serves to bypass the required conversion between the inactive and active forms. Common brands are Armour, Nature Thyroid, and WP-Thyroid. These all contain a 4:1 ratio of T3 to T4 which is thought to be a bio-identical relationship of the hormones found in the body.
I have had great success with these combination products. They do take a little more work, and perhaps more frequent testing to get things right. But like the Synthroid, once stabilized and unchanged, the response is surprisingly stable.
Thyroid Hormone Replacement: Using T3 Alone
The final option is to add in, maybe “sprinkle” is a better word, some free T3 into the mix. This fully bypasses any required conversion of T4 to T3 and has both benefits and challenges. The product is known as liothyronine, or Cytomel.
First; the benefits. It works well. People rapidly notice a change in symptoms. I often add a few milligrams to one of the dosing regimens above. This can be of help if the measured Free T3 seems resistant to rise into the upper half of the laboratory range with the other therapies.
Second; the challenges. This is a more fickle hormone. It works too well. Of the infrequent patients who required lower hormone dosages down because of hyperthyroid symptoms (nervousness, sweating, irritability, high heart rate), many were using Cytomel.
The final “challenge” relates to the half-life discussed above. In contrast to the 7-days required to clear T4, the half-life of liothyronine is hours. This means that to use the hormone effectively, it needs to be dosed at least twice, sometimes three times a day. This is a far cry from the “OK to miss a dose or two” of the levothyroxine.
Finally, this is probably the most expensive option for thyroid replacement.
Thyroid Hormone Management: Conclusions
In conclusion, optimization of thyroid hormone can promote more well-being, better health, and longevity. The three critical considerations for management are summarized below.
First, be sure to measure the hormone correctly. Getting just a TSH as opposed to a full panel that shows what is being seen by the cells, doesn’t provide enough information to manage it well. Measure a Free T3 and Free T4. Reverse T3 is another marker that could be considered, but its use is somewhat out of the scope of this discussion.
Second, get more data. Record how you are feeling, the amount of energy you have, bowel patterns, and objective markers like heart rate and morning (before you get out of bed) temperatures. Show this to your doctor. Make plans based on data, not guesses.
Finally, be creative with the hormonal options at our disposal. There is no cookie-cutter approach that works for everybody. I have provided the benefits and challenges for all of the different permutations. Give the process time. With patience, and by following the data points outlined above, you will realize the benefits of sensible thyroid replacement.