I don’t want that synthetic stuff; I want the natural thyroid hormone.
This is probably one of the most misguided requests I get in my practice. To make sure we’re all on the same page here, I’m talking about levothyroxine vs dessicated (pig/cow) thyroid. First, I must reject the premise of the patient’s italicized statement above.
Levothyroxine is Natural; Pig Thyroid Isn’t
What?! Every other blog I’ve read says the exact opposite!
That’s because none of what you’ve read has been written by an endocrinologist (or at least not an endocrinologist worth her salt). Among endocrinologists, it’s an open secret that levothyroxine is one of the most natural forms of hormone replacement for the human body. When your thyroid is underactive, and your doctor puts you on a levothyroxine pill, the body cannot tell the difference between levothyroxine and thyroxine (the native hormone). In other words, your body is perfectly happy to use levothyroxine just as it was using thyroxine when your thyroid was healthy.
Pig thyroid pills, on the other hand, contain a mixture of T4 and T3, in a ratio of roughly 4:1, respectively. That’s a wonderful cocktail – if you’re a hypothyroid pig. Guess what the ratio of T4:T3 is in the human body – about 15:1! So when you take pig thyroid, you’re getting way more T3 than what the human body is accustomed to seeing on a daily basis. Not good. I’ll explain why shortly.
So we’ve got levothyroxine – a “synthesized” hormone that is identical to the thyroxine that your thyroid would be making if it was functioning properly. And then we have pig thyroid, which gives you both T4 and T3 (two for the price of one!), but in a ratio that is way out of proportion for the human body. Which of these sounds more natural so far?
Well, I’d rather get too much T3 than not enough. After all, if my thyroid isn’t working, doesn’t that mean that I’m not making enough T4 and T3? I have to take at least some T3, right?
You’re still skeptical – I get it. You’ve read that T3 is the “active” form of thyroid hormone that gets inside the cells and gets the job done. The thing is, the body is efficient at taking levothyroxine (T4) and converting it into T3. All the different tissues in the body (liver, kidneys, muscles, brain, etc) are going to make however much T3 they need. Are there instances in which various tissues don’t make as much T3 as they need? Yes, but this is nowhere near as common as some of the non-evidence-based information out there would have you believe. And when it does occur, the magnitude of the impact is probably not as vast as one might think. If you really want to geek out on the T3 conversion issue, read Guidelines for the Treatment of Hypothyroidism: Prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement, and jump to:
13a. Do genetic variants in thyroid hormone pathway genes (deiodinases or thyroid hormone transporters) affect the serum or tissue levels of thyroid hormones in healthy euthyroid individuals or hypothyroid patients taking replacement therapy?
■ Summary statement
Specific polymorphisms in the deiodinases are consistently associated with very small changes in serum thyroid hormone levels. Insufficient data exist to draw any conclusion about the clinically relevant effects of deiodinase or transporter polymorphisms on tissue thyroid hormone levels.
If you like, there’s a plethora of scientific text you can wade through after the summary statement, but I think the more relevant issue to dive into is, why do some people feel better with pig thyroid or when we add liothyronine (T3) to their levothyroxine therapy? And the corollary: if people like pig thyroid, why is your doctor loathe to prescribe it for you?
Five Types of People Who May Need/Like T3
- If someone does have one of those (not clinically diagnosable) deiodinase polymorphisms, it is certainly possible that T3 therapy provides replacement for a physiologic need. In this case, levothyroxine alone might not cut it.
- Patients who have had their thyroids removed have to rely entirely on T4 to T3 conversion for their T3 needs. In other words, an absent thyroid can’t make any T3 at all, so patients with postsurgical hypothyroidism occasionally feel better with combination T4/T3 therapy. Contrast this to the typical patient with an under-functioning thyroid (primary hypothyroidism), who probably makes enough T3 such that exogenous (supplemental) T3 won’t make a difference.
- Hypothyroid patients with depression may benefit from the addition of T3 to their levothyroxine.
- Anyone particularly susceptible to the placebo effect will like T3. Frankly, this encompasses almost everyone – it is rare to be immune from the placebo effect.
- I saved the best for last, because I believe that this is the most common reason why people like T3. T3 is a short-acting hormone that – especially when given in supra-physiologic doses (like pig thyroid!) – tends to act as a stimulant. This is actually true of lots of hormones when taken in higher than physiologic doses. Ever take a whopping dose of prednisone for a few days and feel like Superman? Do you know any body builders who juice and feel fantastic for three days after an injection of 1000mg (venti-sized dose!) of testosterone? So, just because someone feels good on T3 does not mean that she is deficient in that hormone. Smoking crack probably feels pretty good, but you’d never assume the addict has a “crack deficiency.”
Your Doctor isn’t Mean – She Just Cares about Your Long-Term Health
When exposed to high levels of T3, the body may exhibit symptoms of thyrotoxicosis (too much thyroid hormone). Symptoms like heart palpitations, tremors, sweating, anxiety, and insomnia may occur even if the TSH is within the normal range. Remember, while the TSH is usually highly accurate, if you spend part of the day with high T3 levels and part of the day with low levels, that may average out to a normal TSH. In this case, a normal TSH does not mean you are normal.
After longer periods of time, the heart may go into a dangerous rhythm called atrial fibrillation, the bones may become more fragile and prone to fracture, and muscles may waste. So, while your doctor would love to fix all your symptoms right away, a stimulant that masks whatever is really going on with you is probably not the best long-term solution.
OK, I’m hearing all this, but can’t we just check a T3 level in my blood and use that to gauge whether I need T3 therapy?
Oh, were it that simple…the T3 level in your blood does not correlate well with the T3 level in all your various tissues. Remember, each organ is making its own T3 based on its needs at that moment. We can’t measure that. On top of that, when on levothyroxine therapy, the blood level of T3 is usually low-normal and sometimes even slightly low. But there has been no evidence showing that these levels correlate with any symptoms. Bottom line: it is not helpful to check T3 levels in hypothyroid patients on levothyroxine, in an attempt to determine whether T3 therapy is indicated.
How to Broach the Subject of T3 Therapy with Your Doctor
After all that, you’re going to advise me how to actually get my doctor to prescribe T3 for me? Did I misread the first 2/3 of this post?
No, you didn’t misread me. After years of offering small doses of liothyronine to a subset of patients on levothyroxine – in a physiologic ratio of T4:T3 – I am disappointed with T3 therapy and skeptical that it has much benefit. However, I do have a minority of patients who have tried T3 and have had a durable response to it. I say “durable” because patients will often have an immediate benefit from the stimulant effect, which then wanes over the course of weeks to months. If someone still feels better six months after starting T3, I consider that a durable response. So, if a patient meets all of the following criteria, I may offer a trial of T3 therapy:
- The TSH is already in the lower half of the normal range. Sometimes (not all the time), hypothyroid symptoms will improve just by bumping the levothyroxine dose a bit to push the TSH down below 2 – 2.5.
- There is no competing diagnosis to explain the “hypothyroid” symptoms. For example, if a patient has sleep apnea and isn’t treating it because she doesn’t like the CPAP mask, T3 is not yet on the table.
- The patient does not have active heart problems (angina, atrial fibrillation, etc.).
- The patient does not have moderate-severe anxiety. In my experience, T3 makes this worse.
If you feel you meet the above criteria, then consider broaching the subject with your doctor. But you must understand and embrace the following bullet points before you ask:
- If you do try T3, keep your expectations low. Remember, you may feel better when you start it, but that feeling may disappear if the benefit was solely due to the stimulant effect.
- If your doctor went through medical school and residency/fellowship in the 1990’s or after, chances are she has been taught that T3 is unhelpful at best, evil at worst.
- T3 therapy is often associated with naturopathy; the naturopathic approach to hormone treatments is way out in left field and mostly antithetical to the allopathic (mainstream medicine) approach. The number of people I’ve taken care of who have been misdiagnosed and mistreated by naturopaths should be horrifying to the lay public. More on this in future posts.
- Before prescribing T3, your doctor may want to probe aspects of your health and lifestyle that you feel are irrelevant to your symptoms. I recommend you listen to your doctor, as it is impossible to be objective when it comes to your own health. You may “know your body,” but your doctor knows hundreds – if not thousands – of bodies just like yours. I know it’s disheartening to read that you’re not that special, but trust me, you’re not.
If you’re still reading by this point, I assume that you remain interested in discussing T3 therapy with your doctor. Here’s how I would initiate the conversation:
Doc, I’ve been on levothyroxine for quite some time now, and I still have several symptoms that just won’t resolve, like [symptoms]. I realize that my TSH is optimized, which should mean that the treatment of my hypothyroidism is optimized. So I’ve been thinking about what else could be causing my symptoms, and I just can’t come up with anything. I’m getting at least 7-8 hours of sleep every night, I’m eating clean, and I exercise several times per week [this better be true]. Based on what you know about me, can you suggest any other avenues to explore that might help me figure out these symptoms?
Now you pause. Let your doctor earn her $20 copay ($40 if she’s an endocrinologist). Give her time to ask you questions, look at your lab work from the past couple of years, and see if perhaps there is something else to explore. If she has some suggestions, great. If she agrees that you are otherwise healthy, it is possible that she may actually broach the idea of a trial of T3 (this is much more likely if you have a mid-late career Endocrinologist). If she comes up empty and basically shrugs her shoulders, then you can carefully and respectfully bring up the possibility of a trial of T3:
Doc, don’t worry about being out of ideas. I’ve been wracking my brain for [weeks/months/years] and I haven’t come up with any competing diagnoses either. So I wanted to get your opinion about something I read. It was written by an endocrinologist, so I hope it’s more trustworthy than the majority of the nonsense out there on the internet. It seems like there is a small subset of hypothyroid patients who will benefit from adding in a small dose of liothyronine to their levothyroxine. I understand that, when used, the levothyroxine dose should remain somewhere around 10-20 times as much as the liothyronine dose, to keep the ratio close to normal for human physiology. I also understand that it may not work, and I’m ok with that. If it doesn’t work, then I’m happy to stop it. What do you think?
You’ve done several things by couching your request as above. You’ve communicated that you and your doctor are on the same team, and you’ve acknowledged that you don’t expect miracles. You have implied that you understand how doctors feel about internet research and that you understand the limitations of such research. You have asked your doctor to give her opinion of what you’ve read, thereby demonstrating that you respect her education and experience, and you value the doctor/patient relationship. Now the ball is in her court. She can agree to a trial or not. If not, you can try to gauge if there is any wiggle room in that “no.” But if there isn’t, you need to accept that and either forget the trial of T3, or go get a second opinion.
What do you think? Have you tried liothyronine or talked to your doctor about it? What has your experience been with your trial or with your doctor? Are you a doctor who has used T3 for your patients? Do you think it has value? Comment below!
By interacting with me in the Comments, you agree that you have read and will abide by my Disclaimer.
January 28, 2020 Update: The Comments section of this post is now closed. Any further discussion about the issues raised in this article should take place after the appropriate post in my ongoing T3 Controversies Series. For a complete explanation of the rationale for closing this post to new comments, please read Comments and Controversies on Hormones Demystified. Here’s the TLDR version: reader comments on this post have veered off into realms that this blog was created to refute/debunk. Each post in my new T3 Controversies Series will address one specific unsupported claim or falsehood found in the comments on this post. This narrower focus of each post should help keep comments on topic, helping you find the information you need. As always, thanks for reading and staying engaged. -HD