My experience with Low-T3 on Synthroid

My thyroid lab results since 2013. Synthroid dose shown on X-axis.

This case report is based on the graph shown at the top of this article.

If you can’t see the graph, use this link to view it

UPDATE: My Reverse T3 tests finally came in for 18-02-2016, and they were 33 ng/dl, which is far above the upper end of the lab range (8-25) and are literally “off the chart” since the top of the chart is “30.”

I made this graph of my thyroid lab results because I wanted to have something quick & visual to show my own doctors who don’t seem to think there has been any problem with my T4-only, TSH-focused treatment plan.

The graph clearly shows

  • my consistently Low-Total T3 (0.9, 1.0, 0.9, 0.9 nmol/L);
  • and later, consistently Low-Free T3 (2.9, 3.4, 3.4 pmol/L)

All T3 results are below lab ranges, and show on the graph as relatively flat lines.

Thus, my T3 levels stay relatively constant …

  • DESPITE varying T4 (Synthroid) doses (112, 100, 112, 112/125, 125 mcg)
  • DESPITE a varying high-normal Free T4 (25.5, 17.7, 23.9, 20.9, 21.5, 21.6, 22 pmol/L).
  • DESPITE wildly varying TSH levels (0.08, 18.8, 5.02, 4.66, 3.33, 8.05, 3.72, 6.16 mU/L), and Low-T3 even when TSH is “normal”
    • Even when on a constant T4 dose, TSH is not steady over time.  Instead, TSH dips in and out of range and varies by as much as 4 mU/L.

The many numbers in RED show that many of my TSH levels and all my T3 results have been out of reference range for the past 3 years.  I have only been treated by my family doctor with Synthroid (T4-only) therapy, which I’ve been on since 2003. I’ve never seen an endocrinologist.  My family doctor went on vacation starting December so I saw another doctor from the same office, and a naturopath, from whom I asked for Free-T3 and Reverse T3 tests instead of the previous “Total T3” test.

The graph clearly shows I’m unable to raise my T3 with varying dosages of T4. You can see the T3 numbers are basically flat despite TSH going all over … like those shown in the case study article by Tevaarwerk (2014).

The TSH is responding to T4 levels in serum, but the T4 in serum does not always correspond with my dose.

In fact, TSH may be artificially suppressed by high levels of T4 (and Reverse T3).   I may have been more hypothyroid than my TSH was able to show.

Notice that I was on 112/125 constantly from May 2015 until January 2016, with varying TSH levels. Yes, I took my pills religiously every day.

I know that TSH has a daily cycle of variation, but I always take my thyroid pill before bed and then have the lab test the next morning. I also take care to take my Synthroid pill at least 4 hours away from any food and supplements that may interfere with its absorption (i.e. calcium, magnesium, mineral water, caffeine, etc).

Nothing changed much in my lifestyle or diet during the time of the graph.

What is wrong with a Low-T3?

As shown in my earlier post on Low-T3 syndrome, a lot of research shows Low-T3 is very bad for the heart as well as other organs that depend on it.

Low-T3 Syndrome is defined as a below-range T3 while TSH and T4 are in normal range or slightly elevated. Low-T3 can happen even in people with functioning thyroid glands when they are very ill, so that’s why they also call it “euthyroid sick syndrome.”

In almost all studies of Low-T3 (many of which focus on its presence in heart disease), Low-T3 levels are shown to be an independent predictor of a very bad prognosis.

My local lab’s low cutoff for TT3 & fT3 corresponds exactly to the cutoffs in studies of “Low T3 Syndrome” (i.e. Pingitore, 2005; Amin, 2015).

If “Low-T3 Syndrome” is bad enough in the presence of “normal” range TSH in people who don’t have a dysfunctional thyroid, it’s reasonable to think Low-T3 could be worse in the presence of higher TSH levels like mine.

Underlying health

My recent lab results, I assure you, showed no other health problems.  Liver fine, kidneys fine, no infections, no inflammation according to C-Reactive Protein levels, not anemic (according to Ferritin, iron/TIBC saturation %), etc.

I have Hashimoto’s thyroiditis, but both TPO and TG antibody levels were within normal lab range as of February 18, 2016.

My ankylosing spondylitis inflammation in major joints went into remission in 2003 likely due to the commencement of thyroid therapy + Vitamin B5.

I still continued to have Iritis (uveitis) inflammations 1-2x / year and occasional problems with hypothyroid symptoms until 2013, when I changed my diet to Paleo Gluten-free.

After going Paleo gluten-free, I enjoyed 3 years without any Ankylosing Spondylitis or Iritis flare ups whatsoever, and no overt hypothyroid symptoms. It hasn’t raised my T3 to have underlying good health (as lab tests show) and good diet since 2013.

Adding thyroid-targeted supplements (selenium, vitamin D, magnesium, etc) since Dec. 2015 still did not raise my T3 levels above the Low-T3 boundary.

The only problems I’ve been having are mild, lingering hypothyroid symptoms  (fatigue, cognitive symptoms, low heart rate, low temperature, cold extremities, dry skin and hair).  The cognitive symptoms and fatigue suddenly got unbearable on January 15, 2016 when I started to have occasional bizarre sobbing fits while not thinking any sad thoughts at all, and writing/editing tasks took 3-5x longer than they should.  Oh, and an inflamed thyroid gland. I have an ultrasound booked for the end of this month.

But the most distressing problem was that after trying to raise my thyroid dose to get rid of these symptoms, in February 2016, I started having some angina-like heart pains.

Mysterious angina-like heart pain

Yes, heart pains.

Hypothyroidism, especially long-term, as shown on my graph, is known to cause heart problems.

Sure, my ankylosing spondylitis and my sleep apnea could also contribute to heart problems, but it seems clear that the increased Synthyroid dose was a trigger.

It was two increases in T4 doses within 2 weeks, not any rise in serum free T3 levels or TSH, that coincided with my heart pain onset.

  • My family doctor and I raised my dose from 112/125 to 125 on January 20, 2016 because of the onset of hypo symptoms.
  • Still having symptoms that were disrupting my work and life, my doctor agreed to let me try increasing my dose to alleviate hypothyroid symptoms and move my TSH lower in the range.
  • I started having heart pains on February 1, 2016 after taking a higher dose of Synthroid, 137mcg.
  • Also, I started taking an adrenal supplement (Ribes Nigrum liquid, by Gemmo) the night before the heart pains started. However, the heart pains continued daily, with a slight decrease in intensity of pain, after I stopped the adrenal supplement February 20, 2016. Therefore, it is not the adrenal supplement, but something to do with my Synthroid dose.
  • After feeling quite distressed for 3 days of frequent heart pain on 137mcg, I went back to my dose of 125mcg.
  • Still having heart pains several days later on 125mcg, and starting to experience dizziness, I got worried. I was advised by a nurse to take myself to an Emergency department.

My high-sensitivity-troponin level was 4 (detectable, but borderline low) and they could not find anything wrong with me, so I was referred to a heart clinic for further testing. So far, echocardiogram, ECG and Treadmill tests all show normal results. Holter monitoring will occur next week.

However, the usual heart tests don’t always detect problems at the microvascular level. They are focused on the main coronary arteries and heart chambers. It might not show problems with a weakened aorta that may be developing an aneurism or a dissection.

Yes, I’m pretty sure it’s heart pain, not some other common cause of chest pain.

  • Level 1/10 pains come in waves, with spasms on top.  Sometimes the pain is mild enough that I can be distracted by computer work, but several times a day it will be insistent enough to intrude into my awareness and cause distress.
  • Pains move around from central chest area, to upper left heart, to lower left heart, but generally stay in the same place for at least 5 minutes before moving somewhere else.
  • The pain sometimes goes into my armpit and upper left arm.  Sometimes my left arm feels slightly numb down to my hand. Sometimes I feel numbness and strange tightness in my left neck.
  • It sometimes causes nausea, sometimes just a strange feeling in salivary glands.
  • It sometimes causes extreme weakness and unsteadiness in my legs. When this happens, I have to walk slowly, with a wider gait, and gently coax my floppy legs and ankles by using my hip muscles more.  When this happens while standing, I hold onto something for support and try to find somewhere to sit down as soon as I can.
  • Lightheadedness. No, I am not hypoglycemic.
  • Aches come and go in waves with spasms on top, when at rest, and when doing light activity like walking or household chores, and while sleeping they sometimes wake me up. Yes, pains are exacerbated by activity and stress, usually coming on more after doing light chores for 20-30 minutes, or within 2 hours before starting to teach a class.
  • No, it’s not pain from acid reflux. My stomach and digestion from input to output are normal and healthy.  I don’t have any issues with gas or burping. I get pain while cooking (empty stomach), while eating, and/or after eating — It does not matter when I eat or how full my stomach is.
  • No, it’s not pain from lungs or muscles. While having pains, I can breathe deeply (and even sing) without pain increasing. I can twist my body, lift up my arms, etc. with no increase in pain. I can poke my chest in various places without increasing pain.
  • Not heart palpitations. Not fluttering or missed beats, at least not that I am aware of.
  • Heart rate is not correlated with pain. Sometimes my heart rate raises to 85-110 during pain. Sometimes it stays in the 60bpm range during pain. Sometimes after mild activity like cooking, my heart rate stays 90-110 for 10 minutes or more while seated.

Less heart pain on lower T4 dose

Heart pains continued on 125mcg dose, still shown on the lab tests on February 18 but with a higher TSH.

On February 20, 2016, I decided to try lowering my dose to 100 for two days, and then vary between 100/112 on alternating days (using old pills I still had from 2013 prescriptions).

By the second week on that much lower dose, heart pains alleviated in frequency and severity by approximately 30-50%.

Yesterday, after taking 100mcg at bedtime, I had no pains after 7am.

However, going up to 112mcg last night, I woke with heart pains around 6:10am and pains came back in waves every 4 hours or so.

It is puzzling how heart pain could have an effect within 8 hours of a higher dose or lower dose of Synthroid. They say the half-life of T4 is about 7 days.

Something in the T4 pill, or something my body does with it, is causing an effect within 8 hours.

What should I do?

If less T4 is alleviating heart symptoms, it seems to confirm that my T4 dose could be making any underlying heart problem worse. Less T4, perhaps 100 mcg, is the direction I need to go for heart health.

I clearly can’t stay on T4-only treatment for long. Too high a level is dangerous for the heart.

However, too low Synthroid is also dangerous for the heart (my sleep apnea and bradycardia are returning). Being hypothyroid compromises daily functionality. On 100mcg days I get very drowsy and can’t think/speak well by 7pm, and I have to go to bed very early.

And besides, my T3 levels are pathologically low regardless of my Synthroid dose and TSH. Dangerously low for heart health.

I’ve got to get off of Synthroid and onto a treatment that includes T3 … I have a doctor appointment with an endocrinologist coming up in a few weeks.  I eventually want to move to natural dessicated thyroid hormone, but I want to be careful and transition under supervision. I might need to be on T3-only for a while in order to clear out my Reverse T3, which I’m told may take 12 weeks.


  • Amin, A., Chitsazan, M., Taghavi, S., & Ardeshiri, M. (2015). Effects of triiodothyronine replacement therapy in patients with chronic stable heart failure and low‐triiodothyronine syndrome: a randomized, double‐blind, placebo‐controlled study. ESC Heart Failure, 2(1), 5–11.
  • Pingitore, A., Landi, P., Taddei, M. C., & Ripoli, A. (2005). Triiodothyronine levels for risk stratification of patients with chronic heart failure. The American Journal of Medicine, 118(2), 132–136.
  • Tevaarwerk, G. J. M. (2014). Two patients with atypical low triiodothyronine syndrome: primary deiodinase abnormalities? Endocrinology, Diabetes & Metabolism Case Reports, 2014, 130055.




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