Is Your Thyroid KILLING You? Heart Disease

Thyroid & Heart Disease

High blood pressure
Low blood pressure
Slow/weak pulse (under 60 bpm)
Fast pulse (over 90 bpm at rest)
Arrhythmia (irregular heartbeat)
Skipped beats
Heart palpitations
Chest pain
High cholesterol
High triglycerides
High LDL (“bad”) cholesterol
Mitral valve prolapse
Coronary artery disease
High C-Reactive Protein
Plaque buildup
Fluid retention
Poor circulation
Enlarged heart

Need I say more?

“Dana, your cholesterol is very high.”

“Dana, your blood pressure is extremely low.”

“Dana, your heart rate is too low.”

“Dana, your Cardio CRP (c-reactive protein) is far above the normal range.”

Thyroid Disease & The Heart

Within the very first hour that I spent researching the link between heart disease and hypothyroidism, I found hundreds of published scientific studies. Goose bumps rose on my arms as I stopped and stared in shock at what I had discovered.

Circulation is a scientific journal published for the American Heart Association that publishes articles related to cardiovascular diseases. In 2007 an article appeared entitled Cardiovascular Involvement in General Medical Conditions: Thyroid Disease and the Heart:[1]

The cardiovascular signs and symptoms of thyroid disease are some of the most profound and clinically relevant findings that accompany both hyperthyroidism and hypothyroidism. On the basis of the understanding of the cellular mechanisms of thyroid hormone action on the heart and cardiovascular system, it is possible to explain the changes in cardiac output, cardiac contractility, blood pressure, vascular resistance, and rhythm disturbances that result from thyroid dysfunction. The importance of the recognition of the effects of thyroid disease on the heart also derives from the observation that restoration of normal thyroid function most often reverses the abnormal cardiovascular hemodynamics.

According to the Thyroid Federation International:[2]

The heart is a major target of thyroid hormones. Any change in thyroid hormone levels will be responded to by the heart.

Too little thyroid hormone as a consequence of an underactive thyroid (hypothyroidism):

  • causes your heart to beat too slowly or irregularly, to flutter with missing or additional beats. As a consequence bradycardia may develop; this form of arrhythmia leaves your organs and tissues without enough oxygen and nutrients. Severe bradycardia can result in cardiac arrest.
  • causes your blood pressure to change. Over time, high blood pressure will develop with the consequence of developing atherosclerosis, a risk for heart attack and stroke.
  • causes your cholesterol in the blood to rise and calcification, so called plaque, to develop in your arteries and makes them stiff. All these effects increase the risk for heart attack, heart failure and atherosclerosis

T3 Thyroid Hormone & The Heart

In mainstream medicine, Levothyroxine is the most commonly prescribed thyroid hormone replacement drug, with brand names including Synthroid, Levoxyl, Oroxine and Eltroxin. Levothyroxine drugs contain the synthetic form of only ONE thyroid hormone, T4. T4 is only one portion of the thyroid hormone complex. Yes the majority of thyroid hormones produced by the human thyroid gland are T4, however T3 is the most active useable form of thyroid hormone that can be used in the cells of the body. The conversion of T4 to T3 is a critical element in this puzzle. By doctors strictly relying on T4-only medications, they are under the assumption that our bodies are properly converting the T4 to active T3. For many hypothyroid sufferers like me, our bodies don’t convert T4 to T3 properly. Please read my post Top 5 Reasons Doctors Fail To Diagnose Hypothyroidism.

TSH (thyroid stimulating hormone) is the “gold” standard for thyroid diagnosis and treatment in mainstream medicine. Traditional doctors will test TSH and sometimes T4 levels when they suspect thyroid dysfunction, however many do NOT test Free T3 levels. Many traditional doctors will NOT treat patients with natural desiccated thyroid or synthetic T3 drugs even if their patients are not doing well on their T4-only drugs. This focus on TSH and T4 in mainstream medicine is particularly disturbing to me considering the studies published linking low Free T3 levels to heart disease.

In one study, a total of 573 consecutive cardiac patients underwent thyroid function profile evaluation. Based on the results of the 1-year follow-up:[3]

“Low T3 syndrome is a strong predictor of death in cardiac patients.”

In another article published in 2010, researchers wrote:[4]

“several clinical observational studies showing the important role of a low-T3 state in the prognostic stratification of patients with Heart Failure. Independently of the parameter used, all of these studies showed that impaired T4-to-T3 conversion is associated with a high incidence of fatal events consisting of cardiac or cumulative death or of heart transplantation.”

Dr. William Davis is a renowned cardiologist and author of the #1 New York Times Bestseller Wheat Belly: Lose the Wheat, Lose the Weight, and Find Your Path Back to Health. Dr. Davis wrote an article in 2007 for Health Central, T3: The forgotten thyroid hormoneHe wrote:

What does this have to do with your heart? There’s no question that low thyroid hormone levels act as a potent risk factor for coronary heart disease. While we’ve known for years that people with congestive heart failure or are seriously ill have abnormally low T3 hormone levels, two studies have recently found that people with coronary heart disease also have low T3 levels. These two studies now raise the question of whether low T3 by itself could be associated with increased risk for heart disease.

If your doctor refuses to test Free T3 you can order your own lab testing. Yes you can!

Dana, Your cholesterol, heart rate, blood pressure, and Cardio CRP have all improved.

My primary care physician shakes his head in amazement. (I had searched for a great thyroid doctor who explored the thyroid treatment options to find what was right for me. A combination of  natural desiccated thyroid and time release compounded T3 changed my life.)

That’s amazing.

Could there be people on statin drugs and blood pressure medication right now who are actually undiagnosed hypothyroidism sufferers? Or could they be hypothyroid patients insufficiently treated for their condition? Hmmm….

All the heart disease patients lined up to visit cardiologists, could some of them actually be undiagnosed or insufficiently treated hypothyroid sufferers? Hmmm….

All the heart surgery patients, were they tested for thyroid dysfunction before the medications were prescribed and surgery performed? Hmmm….

All our loved ones who have died of heart attacks, strokes or other heart disease complications, did they ever have their Free T3 levels tested?  Hmmmm…..

According to the World Heart Federation, heart disease is the number one killer of women around the world.[5] The Thyroid Federation International estimates there are up to 300 million people worldwide, majority women, with thyroid dysfunction, yet over half are unaware of their condition.[6] Hmmm…


1. Klein, I., Danzi, S. Cardiovascular Involvement in General Medical Conditions: Thyroid Disease and the Heart. Circulation 2007; 116: 1725-1735.

2. Thyroid Federation International. Thyroid and heart. Retrieved from:

3. Iervasi, G MD, et al. Low-T3 Syndrome: A Strong Prognostic Predictor of Death in Patients with Heart Disease. Circulation 2003;107:708-713.

4. Gerdes, A.M., Iervasi, G MD. Contemporary Reviews in Cardiovascular Medicine: Thyroid Replacement Therapy and Heart Failure. Circulation 2010;122:385-393.

5. World Heart Federation. Women and cardiovascular disease. Retrieved from:

6. Thyroid Federation International. Be Thyroid Aware. Retrieved from:

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About Dana Trentini

Dana Trentini founded Hypothyroid Mom October 2012 in memory of the unborn baby she lost to hypothyroidism. This is for informational purposes only and should not be considered a substitute for consulting your physician regarding medical advice pertaining to your health. Hypothyroid Mom includes affiliate links including the Amazon Services LLC Associates Program.


  1. Glen charles says

    I am 58 years old, and was diagnosed with heart failure over a year ago. My main symptoms was fatigue, shortness of breath, and a general sense that these symptoms will keep me out of normal life activities, my symptom was not being able to breathe when lying down basically . I’ve kind of resigned to the fact that this is how life will be for me back until I found herbs that stop this CHF easily and relief all the airways. My wife and her caregiver assume I can’t be as active, and thus I was excused from normal life responsibilities but natural herbs from totalcureherbsfoundation. com really helped a but sometimes I think is God prodigy that I was able to treat my congestive heart failure but total cure herbs foundation herbal formula has a big impact on my recovery because my heart condition has been fully eliminate. They do things for me, and was too happy to comply with their service. This is a equitable of a way to get of your heart failure.

  2. Gillyanne Fisher says

    I have been subclinical hypothyroidic for several years. Also borderline. Recently developed AFib but all medics have told me is that hypOthyroidism is not a factor, Only hyper. Please point me towards relevant articles. Cheers from the UK

  3. Stephanie says

    I have been on Synthroid for 19 years. I was diagnosed with idiopathic cardiomyopathy 10 years ago and recently had an AICD placed. My doctors refuse to acknowledge that the Synthroid is the cause of my heart problems but cannot tell me what else is causing it. I am so frustrated and feel like there’s no hope. Can someone recommend a good Endocrinologist in the CT or NY area?

  4. Over the last year my thyroid numbers and symptoms have been all over the place. About 16 months ago a naturopath added Armour (5) to my levo (125) and in ~some~ ways I felt better. I moved and it took a bit to get into a new ND. After labs she kept me on both Armour and levo and ran labs including food allergy tests. After eliminating those foods I felt pretty good and then I think maybe my thyroid started working a bit better. I began having some hypErthyroid symptoms (poor sleep, unneeded weight loss, racing heart). I went to an MD (left the ND for other reasons) who seems open-minded about thyroid who checked my T3, T4 ,and TSH. T3 was in the lower quarter of standard range, T4 hugging the top, and TSH quite suppressed. I went off Armour and the racing heart was much better. Poor sleep and weight loss continued. New labs still showed suppressed TSH so we went to levo 112mcg. Sleep better but still not great. Weight loss stabilized. New labs still showed suppressed TSH but 10 days in I am having horrible fatigue. My heart feels like it doesn’t have the energy to beat! I have a call in to the doctor to see if she will raise the levo back up to 112mcg. I didn’t feel great on 112 but it wasn’t scary like this.

    One question I have is does anyone know if it’s T4 or T3 that suppresses TSH? Just wondering if maybe just T4 suppresses it. Wouldn’t that be interesting if T4 is what suppressed TSH even if T3 is low. Maybe I just have a T4 to T3 conversion problem. The doctor did suggest I may be iodine deficient. This is possible because when I do use salt it’s typically Himalayan pink salt or Real Salt which are not fortified. My diet is clean, although I have recently been diagnosed with SIBO and taking steps to deal with that.

    The current medical establishment just doesn’t seem to understand how the body works, and doctors are not interested in really listening. They are so focused on rote memorization of symptoms and the medications they were taught in school they are doing more harm than good. The pharmaceutical companies (and now the insurance companies) have a death grip on all of us. Maddening.

  5. Brenda Gardener says

    Research and determination is required. A willingness to fight for your health and clean up your diet. I had an officious endo who blamed me for 3 years for the erratic readings. Fed up I requested a referral to a more modern doctor. I paid for RT3 tests and full blood work. A stint on T3 and now I have stabilised on a natural porcine thyroid extract. $$ expensive but my health is worth it. Gave up gluten and added zinc and Selenium drops plus extra D3 at my new endocrinologist suggestion. Find a medical practitioner who will partner with you for good health.

  6. Good grief. People looking for answers to their thyroid problems don’t need to read a headline that my thyroid may be “KILLING” me.

    • western influences.. are killing you.via cross contamination.. and exposure to round -up.low t3 is never correct.for those with celiacs or IBS. whilst American Medical profesionals.. will watch your immunity health and humanity crumble. 70 percent of celiacs suffer from hypothyroidism. If we were allergic at birth, we would all be on TLC with the wee people. genetics loads the round.environment pulls the trigger

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