Saturday, February 25, 2012

Natural thyroid hormones

Many patients ask about natural thyroid hormones.
Are natural thyroid hormones the best treatment for an underactive thyroid?

That question is not simple. Here is my attempt to make this topic clear for those many people, patients and even doctors, who are confused about natural thyroid hormones.

First, underactive thyroid known as hypothyroidism is easily diagnosed. 
That is, once the diagnosis is considered.
Blood tests give the answer. Not hair tests, not saliva tests. 
Blood tests, properly interpreted can confirm or rule out hypothyroidism.

What blood tests? Endocrinologists are the experts on hormones but you don't have to be an endocrinologist to diagnose hypothyroidism. Hypothyroidism is easy to diagnose with a combination of blood tests called thyroid stimulating hormone, abbreviated TSH, and a blood test for free thyroxine.

If both the TSH and the Free thyroxine are in the normal range, there is no hypothyroidism.  The person who says otherwise is either ignorant, confused or a quack or all three.

Some people dismiss the blood tests and claim that they can diagnose underactive thyroid some other way, like using body temperature. 
I caution you to stay away from those folks. They’re bad news!

The TSH is above the normal range in all patients who have an underactive thyroid if their  pituitary and hypothalamus are normal. If there is pituitary disease, the TSH is not reliable for the diagnosis of hypothyroidism. Those relatively few people with pituitary problems should see an endocrinologist for diagnosis and treatment.

The normal thyroid gland makes two main hormones called levothyroxine or T4 

T4 (levothyroxine)

T3 (triiodothyronine)

and triiodothyronine  or T3.  
T3 has 3 iodine atoms while T4 has 4 atoms of iodine as shown above.

Most of the T3 in the body comes from conversion from T4. T4 is present in higher levels in the blood  than is T3. But T3 is more potent.

Everyone can convert T4 to T3, naturally. Humans have an enzyme called a deiodinase that converts  T4 to T3.

The safest way to treat hypothyroidism is to give the pure active form of T4 called levothyroxine. The levothyroxine found in such branded pills as Synthroid, Levoxyl or Tirosint is the same exact chemical that your thyroid makes. Tirosint has no colorants or fillers.

I usually recommend one of these brands because they reliably contain the amount of levothyroxine that we prescribe. Many doctors find the generic levothyroxines to be less reliable. But as with all generics, generic levothyroxine is cheaper.

And when you give pure T4 in pill form your body can naturally make the amount of T3 that it needs. Remember we all convert T4 to T3.

You say wait, how about pig thyroid gland extracts that contain both T4 and T3 like Armour Thyroid?
Isn’t that more natural?

I have several answers to those questions.
·      If you are reading this, you are not a pig. So Armour Thyroid is not too natural for a human.
·      Your body makes the T3 it needs naturally when it gets T4 and giving it a mixture of the two is like my saying I’m smarter than your body and I know how much T3 your body needs so take this pill. The thyroid extract prevents your body from naturally regulating by forcing  T3 into your body instead of allowing your body to make the T3 it needs.
·      T3 lasts a short time in your blood stream so levels of T3 shoot up and down when you take pills that contain T3. See below.
       These fluctuating levels of T3 can cause shakiness and bone and heart problems.
       But when you take T4 alone, T3 is slowly produced over time by your body with smooth stable safe levels of T3 resulting.

Rapid changes in T3 levels in the blood after a single dose
·      Thyroid extract probably would need to be taken at least two or three times daily since the levels of T3 vary so much and T3 has a short half life.
·         People with hypothyroidism in general feel no better with combination T3 and T4 therapies as compared to T4 alone. Multiple randomized, controlled, double blind clinical trials have shown this to be true in  Australia, Canada, and the U.S.  in 2003, in 2004 in Germany, in 2005 in the United Kingdom, and more recently in the U.S..  One small study conducted in Denmark suggested benefit with the combination.
·      There is concern that batches of thyroid extract pills may vary in their content of T3 and T4.
·      Adjustment of the dosage of the thyroid extract by following blood tests can be extremely difficult since the blood levels of the thyroid hormones and TSH vary widely in patients taking thyroid extract.

Remember that the term natural has no agreed upon definition. In my view, the most natural way to give thyroid hormone is to let your body regulate itself as much as possible naturally. By giving levothyroxine alone, you can do that.

But sometimes patients are on T4 therapy with normal levels of TSH and still feel fatigued or otherwise not right. After thorough evaluation, I find that most of these patients will feel better once the right diagnosis is made and treatment is provided.
Thyroid extract is not the answer.

I hope this post has brought some clarity to the question of natural thyroid hormones.

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