Thyroid Hormone Replacement: Part 2

Thyroid Hormone Replacement: Part 2
istock photo/ivan-balvan

If you need thyroid hormone replacement, it is important to get it right. The most common mistake I see with thyroid hormone replacement is underdosing of the hormone. So many people are left to suffer needlessly due to inadequate treatment.

Let’s put an end to this silly practice right here, right now.

In an earlier blog, I reviewed some of the science around thyroid hormone function, signaling and measurement. I also reviewed the testing used to give detailed insight into the body’s thyroid status and needs.

In this blog, we will go over some practical steps that you can take to really get your thyroid function right on. This is based on my 20 years of clinical experience with thyroid hormone across multiple patients, products and formulations.

Our understanding of thyroid function and the ability to measure it have changed over the last few decades. Let’s make sure that your doctor is not stuck in the thyroid hormone replacement strategies of the Pleistocene era.

Rule #1 of thyroid hormone replacement: There are no rules

Here’s the first most important lesson for custom thyroid hormone replacement. There is no boilerplate right way that works for everybody. Every body is different, and everyone’s thyroid hormone regimen should be too.

Just because a friend/spouse/coworker is on product X doesn’t mean that it will necessarily be the right one for you. This is the first, most essential rule of thyroid hormone replacement.

I have seen so many webpages or chat groups that pan the use of straight T4, AKA levothyroxine (brand name Synthroid). If this is working for you, your numbers look good, and you feel great, there is no reason to change things up.

If it ain’t broke, don’t fix it.

Listen to your body. Learn to do what is right for you

To review, thyroid hormone is a critical piece of our body’s energetics.  It works alongside cortisol and insulin to help manage energy. Management of energy is critical for life and health. When we fall out of energetic balance, we begin to develop symptoms. As symptoms of energy balance increase, changes in the quality and quantity of our life soon follow.

Rule #2 of thyroid hormone replacement: Use all of your data points

Yes, laboratory values can be used to help guide your treatment. But they are not your body, and they may not reflect how you feel.

I had a professor in Medical School who spoke a great truism that’s worth repeating here.

He said “The patient is her/his own biomarker.”

This means that we shouldn’t look only at the lab values. First look at the patient. The patient is showing you how her biology is working.

Too often, we doctors forget to look at the whole patient. We are so caught up in the labs and numbers that we forget to ask the essential question. Start with the simple question, “How do you feel?”

I am going to offer some practical steps that you and your doctor can consider to get things right, but don’t forget to follow how you feel. Be sure to incorporate these following important “biomarkers.”

Clinical signs that your thyroid hormone levels may be low (regardless of “normal” range lab values)

  • Weight gain
  • Fatigue
  • Dry hair, skin
  • Thinning eyebrows, especially on the lateral sides (outer brows)
  • Cold hands and feet
  • Constipation, dry stools. If you are having a bowel movement less than once a day, this may be a clinical sign that your thyroid hormone levels are not optimal.

Objective signs that your thyroid hormone levels may be low (regardless of “normal” range lab values)

  • Low pulse. A normal pulse is between 60-100, although I do not consider a resting heart rate of 99 to be fully normal. We have a finite number of heartbeats in our lifetimes. A lower pulse is generally better, and seems to relate inversely to one’s physical conditioning. If you are not in great physical shape, and you have a slow pulse (40-60 beats per minute) along with some of the signs listed above, there is a good chance that your thyroid function is low.
  • Basal body temperature. Get a good digital thermometer, and check your temperature first thing in the morning. A consistent waking temperature lower than 97° likely reflects some degree of hypothyroidism.
  • I always establish a baseline resting pulse rate, particularly if I am going to push the thyroid hormone replacement with my patients a bit. What surprises me is how infrequently I see a patient’s heart rate increase as we push their thyroid numbers up to the higher ranges of normal.

Signs of hyperthyroidism, or excessive thyroid hormone replacement

  • HIgh pulse, anxiety, shakes, tremors and frequent stooling all suggest that you may have too much thyroid hormone on board. Be sure to match these findings with  comprehensive thyroid testing, and make the necessary adjustments.
  • Resting pulse >100

Optimize your thyroid health by using both clinical and laboratory evaluations

At this point, you have probably taken some time to reflect upon your clinical state of thyroid function. The following section dives into the nitty-gritty of getting thyroid hormone right.

First, have you had the correct lab tests performed? Be sure to look at this blog to review thyroid lab testing. Using these numbers, and your body as a biomarker, I will illustrate some actionable steps to best replace thyroid hormone.

Measure TSH and the hormones Free T3 and Free T4

Recall that all of these numbers, ranges and recommendations must be taken in context with the two critical questions: How do you feel, and where are your free hormones?

These two questions must be a part of your thyroid hormone replacement equation.

My patients feel the best when their free hormones are at least in the upper half of the normal range, if not the upper third

Below, I list the four fundamental markers to reliably measure thyroid hormone. The ranges are those published by Quest Labs. Your lab’s ranges may be slightly different.

TSH: Range 0.4-4.5. Optimal .5-1.5 mIU/L. In my practice, a TSH greater than 3.5 is suspect. If it is greater than 4, I will be checking for autoimmunity with TPO (thyroperoxidase) and TG (thyroglobulin) the next time we do any lab work.

Free T4:   Range .8-1.8 ng/dl. I feel optimal T4 is in the 1.1-1.4 range. Recall that this hormone, generally speaking, is a prohormone. It doesn’t have much biological activity in the cells. It needs to be converted into T3, the active hormone that speaks to our cells’ DNA.

Free T3: Range 2.3-4.2 pg/ml. This is the “money” hormone. In my two decades of working with thyroid hormone, I can say that most people feel the best when their free T3 is in the 3.2-3.6 range.

Reverse T3: Range 8-25 ng/dl. As a rule, lower is better. A RT3 greater than 15 suggests poor conversion of T4 into T3. This may be important when we discuss replacement strategies. If a patient has a high RT3, giving higher doses of T4 may only increase this number, and effectively worsen their hypothyroid state.

Smart thyroid hormone replacement: Putting it all together

A comprehensive plan incorporates how an individual feels, their clinical signs (above), laboratory measurements, and finally cost. Some patients want to see if they can influence their thyroid numbers with nutritional supplements, so we’ll start there.

Consider nutritional supplementation for only mildly dysfunctional thyroid function

Mild hypothyroidism may be a transient state in response to stress, cortisol, and nutrition. When this is the case, the first step is to offload stressors, stop overtraining and reconsider your calorie-restricting diet. These factors unquestionably lower thyroid hormone.

In the thyroid gland, thyroid hormone is built with the amino acid tyrosine, the metal selenium, and the mineral iodine. It makes sense to first supplement with these components to see if normal thyroid function can be restored. But don’t try it for too long.

For a combination supplement, I like the Thorne product Thyroscin. It contains all of these elements, without too much iodine.

And speaking of iodine, be careful here. HIgh doses of iodine can paradoxically suppress thyroid function (Wolff-Chaikoff Effect). I won’t use more than 1 mg of iodine daily.

If your provider is having you use Lugol’s solution or Ioderal, or can’t tell you exactly how many milligrams you are taking daily, I recommend that you think twice. I commonly see people whose iodine levels are way too high on these well-intended interventions.

Pharmacological options for thyroid hormone replacement

There are basically three possible interventions for hormone replacement. They are T4, T3, and combinations of T3 with T4. Each of these hormones are “bioidentical”, meaning the active hormones are the exact molecules that are normally made in the thyroid gland.

Thyroid hormones are dosed in micrograms, millionths of a gram. For this reason the medication needs to be put in a tablet or capsule with some filler.

Some common formulations are listed below.

The generic form of T4 is known as Levothyroxine. It is inexpensive, but as a generic may have different allergens in the filler because of different manufacturers.

Synthroid or Levoxyl are mainstream products containing only T4, but have lactose and cornstarch as inactive ingredients. I have seen patients with lactose intolerance struggle with these brands.

Tirosent similarly has just T4, with the slightly cleaner fillers of gelatin and glycerine.

All forms of T4 require conversion to T3 to deliver active thyroid hormone

Clinical note: These single element T4 formulations are commonly used, and I have seen many patients do great with these alone. They do require conversion to T3, which is generally not a problem in patients with normal adrenal function. The half-life of these formulations is long, which lessens day to day variability. I have found that when a patient stabilizes well on a pure T4 product, they can remain very stable on the same dosage for years.

Combination products for thyroid hormone replacement: T4 with T3

This hormonal combination provides 38 ug of  T4 with 9 ug of  T3 dosed in  “grains” or milligrams. One grain is approximately equivalent to 60 mg. Most can be dosed in ¼ grain increments (except Armour). Sometimes it takes a little math and creativity to get these dosages right.

These dessicated hormone products are processed from live animals, typically cows and pigs. I have had some patients who declined using a dessicated product for this reason.

Armour thyroid is perhaps the most commonly prescribed dessicated thyroid replacement hormone. I take it and it works, but it offers fewer dosing options, and can be more expensive than NP Thyroid.

WP Thyroid, NP Thyroid and Nature Thyroid all have the same T4/T3 ratios of the Armour thyroid listed above. These brands can be more difficult to procure due to recent national shortages, but are thought to be “better.”

An advantage of the dessicated thyroid products is that in adding T3, any T4 to T3 conversion problems can be bypassed. T3 is available immediately to the body; it doesn’t need to be made.

Cytomel, or liothyronine are both pure T3, no chaser. Unlike T4, which tends to level off over time due its long half-life, T3 is metabolized quickly. For the patient with normal T4 and low T3, I will often use this alone. T3 requires dosing twice a day, so it is less convenient than T4. But it works well.

Work with your doctor to optimize your thyroid hormone health

It may take some negotiation, and some false starts to get things right with your thyroid, but you can use this information to communicate with your doctor.

The important tip is to start somewhere, assess, and make changes. All of these different formulations can be used alone and in combination with one another.

The most important thing is to continue to circle back to the main questions of how do you feel, and where are your biomarkers? If you can start there, then add in the labs that best depict your true thyroid functioning, you will have all of the data that you need to get your thyroid spot-on.

Be sure to test, and then retest again until you feel good and the free hormones are in the upper registers. Generally an interval of a month is required after a dosage change for the dust to settle.

Remember that you are your own best biomarker

Here’s the bottom line. Most people feel their best when the free hormones are greater than the 50% to 75% of the labs range. If you are not showing evidence of hyperthyroidism (see above), you are probably not overcorrected.

If I raise up my free hormones, won’t my TSH get too low?

As the hormones are replaced, what happens to the TSH? Based on my last blog about the negative feedback loops, shouldn’t the TSH drop?

I would expect it to drop. And it does.

Occasionally as we push the free hormones up into a more physiologic range, the TSH goes below the “normal range.” This all makes sense. The brain is not needing to signal to the thyroid to make additional hormone. The medication is providing sufficient hormone.

This begs the crucial question, which we actually answered earlier in the blog.

Do we follow the TSH, which would be expected to be low through negative feedback? Or do we follow how the patient feels, resting pulse, basal body temperature and free hormone levels kept in the upper half to quarter of the lab’s range?

This is a good time to revisit the first two rules of thyroid hormone replacement.

The first was that there were no set rules. We need to use a constellation of good clinical judgement, creative hormone dosing, and accurate lab testing to determine what is best for each individual.

The second was to use all of your data points. And don’t forget to ask how you feel on the treatment.

After all, you are you own biomarker.


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