Low free T3 can increase heart disease

[Nelson Vergel]

Low serum free triiodothyronine levels are associated with the presence and severity of coronary artery disease in the euthyroid patients: an observational study.

Ertaş F, et al. Anadolu Kardiyol Derg. 2012.



Abstract

OBJECTIVE: The aim of this study is to investigate the relationship between serum thyroid hormone levels that are within the normal range and the presence and severity of coronary artery disease (CAD) in patients referred for coronary angiography.

METHODS: In this observational study, we enrolled 119 consecutive patients (77 men, mean age 60.7±13.8 years) who underwent coronary angiography. Blood samples were tested for thyroid stimulating hormone (TSH), free triiodothyronine (FT3) and free thyroxine (FT4) concentrations. Additionally, risk factors, clinical characteristics and angiographic results were obtained. The patients were separated into two groups according to the Gensini score as those with mild or severe atherosclerosis. Statistical analysis was performed using the Chi-square, Mann-Whitney U, correlation and logistic regression tests, and ROC analysis.

RESULTS: FT3 levels were significantly lower in subjects with CAD (4.0±0.7 vs. 4.6±0.6 pmol/L; p<0.001). Moreover, lower FT3 levels were found in patients with severe atherosclerosis (3.9±0.7 vs. 4.5±0.6 pmol/L; p<0.001). Logistic regression analysis demonstrated that the lower FT3 levels were associated with the presence (OR =0.266, 95% CI: 0.097-0.731, p=0.01) and severity (OR=0.238, 95% CI:0.083-0.685, p=0.008) of CAD. In the ROC analysis, a level of FT3 ≤4.2 pmol/L was found to predict the presence of CAD with 69% sensitivity and 71% specificity (AUC:0.744, 95% CI:0.653-0.834, p<0.001); and the severity of CAD with 75% sensitivity and 67% specificity (AUC:0.733, 95% CI:0.642-0.824, p<0.001).

CONCLUSIONS: FT3 levels within the normal range were inversely correlated with the presence and severity of CAD. Moreover, lower FT3 concentrations were correlated with the Gensini score and independently predicted the presence and severity of CAD. Thus, the FT3 levels may be used as the indicator of increased risk for CAD.

Check your free T3: Free Triiodothyronine T3

 

[Vince]

Dr. Bernstein on Hypothyroidism

Hypothyroidism is an autoimmune disorder just like diabetes. So we find that autoimmune disorders come in clusters. I don't think that I ever found a patient that had only one autoimmune disease. For example, almost 100% of my patients have diabetes and psoriasis - at least mild psoriasis with rough elbows. About 80% - 85% of patients are hypothyroid etc. The hypothyroidism frequently occurs long before development of diabetes in some individuals, and in other individuals hypothyroidism develops long after the onset of diabetes. But for most diabetics, hypothyroidism comes along sooner or later - that is inadequate activity of their thyroid gland.

I might add that until last week, I had never seen a hyperthyroidism - too much thyroid activity in a diabetic. Then a young lady came along whose thyroid levels were high and she had a rapid heart rate, and I was sure that she was hyperthyroid. I ordered a rerun of her bloods, and low and behold, it came back - the thyroid test came back normal. So she was not hyperthyroid. This means I have absolutely no experience in 30 years with any hyperthyroidism.

Now hypothyroidism can present with a number of symptoms including no symptoms whatsoever. I occasionally will see a patient who feels perfectly fine, but his thyroid levels are low. Quite frequently, we see lipid abnormalities - things like high LDL, small dense LDL particles which are atherogenic - possibly low HDL - supposed cardiac risk factors. And indeed low thyroid does have strong association with heart disease, and it can be corrected by correcting the thyroid status as we will discuss. Tiredness is a very common symptom. Poor memory is a very common symptom of low thyroid. Many of my new patients can't remember what I teach them. Lucky I record everything I teach and give them the recordings. But many people don't remember instructions because their thyroid is low. I even have a memory test that I give every patient, and it tends to improve both with blood sugar improvement and with correction of the low thyroid status. Depression is a very common side effect of hypothyroidism. In fact, it is now standard protocol for psychiatrists not to treat depression until they have gotten a thyroid profile, and if the patient were hypothyroid correcting the thyroid status before any other kind of treatment. Hair loss can occur - very commonly there is loss of hair in the outer 1/3 of the eyebrows - not just on the head, but also the outer 1/3 of the eyebrows. Dry skin. You could look up hypothyroidism on the internet, and you will get many more of the possible symptoms.

Now the thyroid gland makes two major hormones and a number of minor hormones. The two major ones are T3 and T4. T3 is also called liothyronine, and T4 is called levothyroxine. T4 has four iodine atoms in the hormone molecule, and T3 has three iodine atoms. The major hormone made by the thyroid is T4, but T3 is far more active than T4. T4 gets stored in the tissue throughout the body and is converted to T3 as that particular tissue requires it. Each tissue has its own deiodinase enzyme that removes one of the iodines from the T4 to convert it to T3. T3 is the active hormone.

We can treat the disease by giving T4, and then hoping that the patient will convert it to T3 as needed, but all too often T4 does not get adequately converted to T3. In fact, I find that many of my diabetic patients may have a normal T4, but a low T3. These people lack the enzyme that converts T4 to T3. We can double check by looking in their blood for reverse T3 which is an inactive form of T3, and it is frequently elevated in people who cannot make adequate amounts of active T3. When we test for low thyroid, the most important thing to test for is free T3 which is the active form of T3. The inactive form is T3 bound to protein molecules or globulins in the blood. So we want to see free T3. We might also take a look at free and total T4. But the most important one is the free T3. I usually measure free and total T3 and free and total T4 - although I'm might be wasting a little of the insurers money cause I could get away with just the free T3.

I will treat the patient usually with both T4 and T3. In the hypothetical patient who only has low T4, I will give him a product called Synthroid or the equivalent which is levothyroxine - but that's rarely the case. Most often, people have slightly low (free) T4 and very low (free) T3. And we have to give those people T3 replacement which is liothyronine. Liothyronine comes under the brand name Cytomel. But Cytomel only comes in multiples of 5 mcg, and what if a person needs 17 mcg a day; you cannot get it from Cytomel. Another problem of Cytomel, is that it has an active life of about 8 hours. So you have to take it every 8 hours, and almost everyone forgets the afternoon dose. So what I almost always prescribe is a compounded liothyronine that we purchase from a compounding chemist - actually the patient purchases it either from a compounding chemist near me or in the patient's home town. And the compounding chemist will make up timed released liothyronine or also called "slow release" T3. And the T3 can be made in any strength that the doctor wants, and it is taken every 12 hours not every 8 hours like Cytomel because this now is a timed released version. And I will guess at an initial dose. I may even have some samples in my office which I will try on the patient a few days, and if we get reversal of symptoms without undue side effects, we will start them off on a trail dose twice a day every 12 hours. We will measure his blood levels in 2 - 3 weeks. And we keep titrating the T3 until we get blood levels in the middle of normal range.

I want to give you the exact specification of the test that we order from laboratories. We usually have the tests performed at Nichols Institute in California, but Mayo Clinic labs also is a good endocrine lab in that they can do these tests. We do free T4 by direct equilibrium dialysis/radioimmunoassay, and total T4 by chemiluminescence. Free T3 and Total T3 by tracer dialysis. Steve Freed has list of these tests, and if you weren't able to write them down, you can email him and he will get them for you. The diagnostic code that we give the laboratory is 244.9.

When I order thyroid test, I also get a white blood cell (WBC) count because it tends to be under 5.6 for hypothyroid people. And when we give them thyroid replacement white blood cell count tends to come back over 5.6 which would make it more normal.

Anyway, getting back to the T3 replacement slow release liothyronine, you take it every 12 hours, but you do not take it concurrently with high fiber foods like bran crackers - should be at least 2 hours away from taking T3 and T4. You don't take T3 and T4 with zinc, selenium, calcium, magnesium - at least 2 hours away. And you don't take it concurrently, any of the thyroid products concurrently with soy products. So you should be at least 2 hours away from metals, fibers, and soy. I doubt that a small salad would make much difference, but I'd certainly keep it away from bran crackers. If you're taking psyllium powders (Metamucil, etc.) for constipation don't take it at the same time you take thyroid pills. In any event, we titer up the T3 and many cases simultaneously also T4 until on testing T4 levels and T3 levels are right in the middle of the normal range. Now it takes 2 months for T4 levels to equilibrate once you're on a dose of levothyroxine, and it takes only about 2 - 3 weeks for the T3 levels to equilibrate. So, we can rapidly fine tune T3 levels, and we slowly fine tune T4 levels.

That's basically the story. I've been prescribing - ah - diagnosing and treating hypothyroidism in this manner for 30 years. And it was born out of trial and error, and watching the results. For example, most doctors test the TSH (thyroid stimulating hormone) on the assumption that it reflects hypo or hyperthyroidism, but I never saw any correlation of TSH with either symptoms, lipid profile, or with a low white blood cell count. It seemed to be no relationship to hypothyroidism. So I abandoned its use many, many years ago. All of this that I am telling you was based on trial and error, and my observations.