Raina Kranz, C. P. T.,
Thyroid Nation

What is the correlation between Heart Disease Risks and Thyroid Hormone levels?

Having thyroid disease and managing it can be very confusing and frustrating for many thyroid patients. Our goal of feeling better and trying to maintain good health is a constant daily battle. And worse, it is extremely challenging to find the right doctor who can help us. The information highway has brought to our fingertips loads of valuable information, but deciphering through the facts from the theories is impossible for most. How do you know what is true or false, what is wrong or right or safe or unsafe? We depend on our health care givers to supply us with the information we need – but often times we are left holding a bag of unanswered questions.

I have been plagued by this very situation for some time now. The most concerning for me is the goal of optimal thyroid levels and what those levels or guidelines should actually be and why. At what level would thyroid levels actually be optimal for thyroid patients and at what level should we be at, to prevent other diseases from manifesting? The reason for this concern is due to a pattern I have been witnessing in the thyroid community and I needed answers. I have spent countless hours addressing low –T3 syndrome, euthyroid sick and the complications to heart disease with too low ft3 and T3 levels. As of late, another pattern has been emerging and a set of symptoms that appear to be related to the heart as well.

The alarm is around the increase in heart related occurrences with in the thyroid community, as well as the increase in anxiety, insomnia, insulin and leptin resistance and Type 2 diabetes. You would think once starting thyroid hormone replacement that all the health issues related to thyroid disease would diminish and it would be as simple as maintaining a given thyroid level. It is much more complicated than that.

Let’s talk untreated thyroid disease and complications to heart health…

When the TSH is elevated above normal (>4.5), whether it be sub-clinical hypothyroid or diagnosed hypothyroid with or without autoimmune disease, this alone increases the risk of atherosclerosis, increased total cholesterol and a higher LDL to HDL ratio and metabolic syndrome. When the TSH is too low (<.40), indicating hyperthyroid and or Graves’ disease, a higher risk heart attack, stroke, anxiety and osteoporosis may affect the individual. One can also have structural issues with nodules and possible cancer without having either autoimmune disease. But, having Sub-clinical hyperthyroid or hyperthyroid increases the risk of having a cardiovascular event. The obvious reasons for being medicated with either Thyroid hormone replacement or anti-thyroid medications, is to prevent heart disease or any other secondary disease that can develop by not being treated for  thyroid disease.

There are many ways in which one can acquire heart disease, genetics is the most common and in some cases, hard to prevent. Lifestyle changes, exercise and eating habits can all be altered, but for some this may not be enough. The body is an amazing thing and it does what it wants to do… this is why it is imperative that some people must be on a statin, because without it their risk of a coronary event is inevitable. Some are able to reverse their risk factors by removing bad habits and incorporating goods ones.

The heart, an organ that is as important as the thyroid gland when it comes to the inner workings of the body.  Its health and ability to function depends on many things, but the important thing is the ability to pump blood from the heart to circulate through the respiratory system, the muscular body, to the brain and back to the heart without fail. The heart itself is a muscle, similar to any other muscles in the body…it has strength and it has endurance. The stronger the heart, the more blood it can pump out in one beat. This is called, stroke volume. The more blood moved with less beats per minute the more fit the heart will be. Muscles contract, organs do their jobs and we as a person can move and breathe with ease. An un-fit heart will have to beat many more times in order to get out the same amount of blood in one beat of a healthy-fit heart. What this means is a fit individual will have a lower resting heart than an unfit individual. It also means that on exertion the fit individual will have the heart strength to move the amount of blood needed with ease and be able to sustain a given intensity for a longer duration, whereas an unfit person will tire easily.

With hypothyroid, heart rates and blood pressure tend to be lower. Resting heart rates will be lower but, this does not mean that your heart is fit. There are many people who genetically have lower resting pulses and blood pressure and they suffer from health issues, as well. A slow pulse with an unfit heart will also be unable to meet high demands or even light exertion. These individuals may also experience dizziness upon standing; this is due to blood not being able to get from the lower extremities to the brain fast enough. Hypothyroid tends to slow everything down and that includes metabolism and weight loss.


Hyperthyroid is exact opposite, everything tends to speed up including heart rate, blood pressure, metabolism and anxiety. This state puts a lot of strain on the heart and is a high risk factor for a cardiovascular event. An increased heart rate and blood pressure for an extended period of time is not good for overall health.

What I would like to present to all of you, is some very simple yet astonishing facts about thyroid disease and its direct correlation to heart disease, type 2 diabetes, metabolic syndrome, insulin and leptin resistance and even PCOS. The purpose of this article is to shine a light on what is known to increase risk of these diseases and how actual thyroid levels are a contributing factor. That being said, take into account that this information not only goes for diagnosed thyroid disease but also those who are normal,healthy, people without thyroid disease. (The only exception to this information is those who have survived thyroid cancer.)

We all are aware of the risk factors of non-treated thyroid disease, but are you aware of the parameters of being treated, may actually be causing us health issues as well? Based on the information being shared with in the thyroid community, I do not believe we have enough information on this subject at all and our aim to be optimal may be causing us more harm, than the wellness- we seek.

In a large study, done in February of 2014, 2,524 generally healthy subjects between the ages of 35-55 years old (both men and women) with whom,

– None of which were using thyroid medication
– Thyroid antibodies were not above clinical cutoff values
– Nor TSH outside the reference range (0.27-4.2mU/L).
– 27% of the women and 47.5% of the men were overweight
– 13% of the women and 17% of the men were obese
– 27% of the subjects were active smokers

The aim of the study was to investigate whether serum (TSH) and the Ft3 to Ft4 ratio are associated with metabolic and adiposity-related cardiovascular risk markers, in a healthy population of men and women.  The results left me shocked, to say the least, but it also confirmed many of my concerns, when it came to thyroid community.

The findings are as follows:

In healthy euthyroid middle-aged men and women….
-higher Ft3 levels, lower Ft4 levels and thus a higher ft3 to ft4 ratio are consistently associated with various markers of unfavorable metabolic profile and cardiovascular risk.

In a similar study, done in 2011 – Higher fT3 levels within normal range was found to be associated with metabolic syndrome components in type 2 diabetic subjects with normal TSH and Ft4.

Essential-Oils-Ad2-Thyroid-NationA year earlier in 2013, the same study that found higher fT3 levels and lower ft4 levels increased cardiovascular risk, also found that that the same values affected cardiac function and structure. More specifically, a smaller left ventricle cavity size, along with increased relative wall thickness. In the earlier study though, significant findings were added with a lower TSH (0.5 – 2.5) and higher ft3 levels, lower ft4 levels, were directly associated negatively with left ventricular end-diastolic volume and increased wall thickness. The total T3 was associated with enhanced ventricular contraction and both Ft3 and TT3 were associated with late ventricular filling. These levels affect the heart, heart rate, function and structure of the heart adding to the risk of cardiovascular disease.

Another large study in November of 2014, researched Ft4 and metabolic syndrome in 5,786 euthyroid subjects over the age of 20, 3755 were euthyroid without a history of thyroid disorders, diabetes or use of steroids or lipid-lowering agents. There findings are as follows; ft4 was associated positively with High-density lipoproteins (HDL), Low-density lipoproteins (LDL), Triglycerides, waist – circumference, systolic BP, and diastolic BP, insulin in a positive way. While Serum fT4 was negatively associated with metabolic syndrome, the lower serum fT4 has 30.1% higher odds of metabolic syndrome and insulin resistance and higher fT4 has a 22% lower risk of metabolic syndrome and insulin resistance.

The connection between thyroid function, serum leptin, lipid metabolism and insulin resistance in polycystic ovary syndrome was studied in 2003. The aim of the study was to determine if serum leptin levels is regulated by thyroid hormones, lipid metabolic products and insulin resistance in women with PCOS.

It was a small study of 72 women. Twenty-five lean, nine-teen obese and twenty- eight of normal weight. The findings were also astonishing; Serum leptin levels were higher in the obese group and serum ft4 levels were lower in both the obese and lean group with (PCOS) than the control group. The women in both groups were also hyperinsulinemic and insulin resistant. Higher total cholesterol, very low density lipoprotein and Triglycerides were significantly higher in the obese group and High density lipoproteins were much lower.

A significant correlation was found between serum leptin levels and both BMI and insulin resistance in PCOS. Serum fT4 and lipids had a poor correlation on the regulation of serum leptin levels, BMI and insulin resistance may play a key role in PCOS.

You cannot ignore, even in this small study, the lower levels in Ft4 with all the women in the study. I think further study on this subject is warranted.

Most concerning is a study done on healthy pregnant women and their ft3 to ft4 ratio and metabolic phenotype. A metabolic phenotype is a term for a measurable set of metabolites whose abundance in bio fluids accurately reflects an individual health status. It’s a blueprint of health. They found that lower TT4 and fT4 within euthyroid range has been shown to be associated an adverse metabolic phenotype. Decreasing fT4 and an increasing fT3 to fT4 ratio in women without prior history of thyroid dysfunction (a higher conversion of fT4 to fT3) were found to have a less favorable metabolic health status along with more placental growth. The clinical significance could include atherosclerotic lesions along with plaque and inflammation.

So what do we know? What have we learned?

We know untreated thyroid disease increases our chances of type 2 diabetes and cardiovascular disease. It doesn’t matter if you’re untreated hyperthyroid or untreated hypothyroid, the risk is the same; which means TSH out of normal range (too high or too low) increases our risk of a secondary disease.

What does it mean when we are being treated?

According to the latest finding, those without thyroid disease who had a lower TSH (.50-2.5) along with a higher ratio of fT3 to fT4 levels have increased risk of metabolic disease and alterations in heart function and structure. This is due to the elevation in heart rate > 90 beats per minute at rest and elevated blood pressure 24 hours a day. Higher levels of fT3 in the blood stream with lower levels of Ft4 and a TSH (.50-2.5) are contributing factors to cardiovascular disease and structural changes with heart. These ranges should be noted they are within normal range. What must be looked at here the significance of the higher ft3 ratio to ft4- – the significance of increased risk would be even higher if Ft3 was not only high but, high out of range- even more so if TSH is too low out of range.

It has also been determined by the research that the higher in normal range ft4 is positively associated with a better lipid profile, BMI and glucose levels and a lower risk of metabolic syndrome and cardiovascular disease.

If these are findings of increased risk for those without thyroid disease, what does this mean for us WITH thyroid disease? This should redefine what we knew and believed to be optimal levels.

Where did these charts come from and where is the scientific information backing them up? I have not found anything that says that all thyroid patients need to have to a TSH as low as possible to ‘0’. In fact, I have only found research implementing this protocol for THYROID CANCER patients. I have never found one abstract suggesting that shutting down the negative feedback loop – the natural process of thyroid hormone production in the humans and animals – is the protocol for all thyroid patients.

That would mean you would have to be medicated enough to lower the TSH to suppression , as close to “0” as possible. Which, in turn, could lower fT4 to the low end of the normal range or lower.  This is increasing the ratio of fT3 /ft4.  That is the exact conclusion of the studies listed above which, has shown to increase metabolic and cardiovascular disease.

The over medication of thyroid hormone replacement to achieve these optimal levels for well-ness could be self-induced increased risk. This situation will cause a constant elevation in heart rate and blood pressure and in most cases of un-fit individuals, which is two-fold stress, on the heart. Alterations in heart function due to stress will cause thickening in arterial and Ventricular walls, slow left ventricle filling and increase fasting glucose. Not good.

The difference between thyroid patients and non-thyroid patients with this research is:

We have the perfect excuse to maintain the most optimal thyroid levels for our health AND we have the medicine to do it. We need to start paying attention to our heart health not just our thyroid health. We should be conscious of the signs and symptoms that cause stress to our heart. How thyroid hormone replacement medicine is affecting our thyroid levels and what that means for our increased risk of metabolic disease, type 2 diabetes, heart disease and PCOS, should be taken into account.

I believe it is safe to say that having a suppressed fT4 is not healthy for anyone and it is especially not healthy for those, like us, with thyroid disease.

The other thing to consider with these findings:

Elevated too high fT4 would indicate hyperthyroid…and a too low fT4 level would indicated hypothyroid. Just using common sense, TSH too low, fT4 too low and high fT3… has two implications 1) Hyperthyroid component with TSH/ft3 and a hypothyroid component with low fT4, which may explain many of the mysterious symptoms that seem to plague those with these thyroid values. 2) Rare pituitary issue or what is called secondary hypothyroidism.

Normal reference range for testing 

  • TSH (.30-4.5)
  • Ft4 (0.8 – 1.8 ng/dL) (10 – 23 pmol/L)
  • Ft3 (2.3- 4.2 pg/mL) (3.5 – 6.5 pmol/L)

Where should levels be for optimal health? 

  • TSH (.50- 2.5)
  • Ft4 (1.4- 1.7ng/dl) or (14-20 pmol/L)
  • fT3 (2.5 – 3.5 pg/mL) or (4.0-5.5pmol/L)
  • http://www.ncbi.nlm.nih.gov/pubmed/24032604

Triiodothyronine and free thyroxine levels are differentially associated with metabolic profile and adiposity-related cardiovascular risk markers in euthyroid middle-aged subjects.


We have previously shown that in healthy young men, a less favorable body composition is associated with higher free triiodothyronine (fT3) levels within the euthyroid range. Besides, a higher free-triiodothyronine-to-free-thyroxin (fT3-to-fT4) ratio has been related to a less favorable metabolic phenotype and more placental growth in pregnant women. In the present study, we therefore investigated whether serum thyrotropin (TSH), thyroid hormone levels, and the fT3-to-fT4 ratio are associated with metabolic and adiposity-related cardiovascular risk markers in a healthy population of middle-aged euthyroid men and women.

Thyroid parameters were measured in 2524 generally healthy subjects from the Asklepios Study (35-55 years, mean age 46 years). Analyses were restricted to 2315 subjects (1138 women and 1177 men), not using thyroid medication, not having anti-TPO levels above clinical cutoff values or TSH levels outside the reference range (0.27-4.2 mU/L). Twenty-seven percent of the women and 47.5% of the men were overweight, while 13% of women and 17% of men were obese. Twenty percent of the subjects were active smokers. Serum thyroid function parameters were determined by electrochemiluminescence.

fT3 and the fT3-to-fT4 ratio were positively related to body mass index (BMI), waist circumference, and components of metabolic syndrome, that is, triglycerides, systolic and diastolic blood pressure, and fasting plasma glucose, and negatively with HDL-cholesterol levels, whereas fT4 was negatively associated with BMI, waist circumference, and triglycerides (p

In healthy euthyroid middle-aged men and women, higher fT3 levels, lower fT4 levels, and thus a higher fT3-to-fT4 ratio, are consistently associated with various markers of unfavorable metabolic profile and cardiovascular risk.

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About the Author

Radiant-Raina-KranzRaina Kranz, C.P.T. attended and is certified from the American College of Sports Medicine. She studied Kinesiology/Biomechanics. Living in Hollywood, Florida she is a full time personal trainer and coach. Find her at her website, Personal Fitness Training Florida and wonderful online Facebook Group, Thyroid Healing Journey. Click to schedule an appointment or to learn more about Raina’s Customized Thyroid Exercise Training Program at Thyroid Trainer.

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