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Thyroid Replacement

Understanding the Dose

The typical form of thyroid replacement we use is called levothyroxine. It’s made of thyroxine, or T4, which is the form of the hormone that comes from our thyroid gland. There are brands like Synthroid or Levoxyl. The way the dosing is written is a little confusing. We usually have medicines that are dosed in milligrams (mg). Levothyroxine is so small it’s always one-hundredth to one-tenth of a mg (ie, 0.10 mg). It’s easier to describe the dose in terms of micrograms (mcg). For example 100 mcg instead of 0.10 mg. So I prefer to say “100 mcg” even though your pill bottle may say “0.10 mg”.

Isolating the Dose

Many things can interfere with how it gets absorbed into your body. Therefore it is important to try to isolate the pill. Try to take it first thing in the morning at least a half hour (preferably an hour) before any food or other pills (especially vitamins, especially iron). Unfortunately even coffee has been shown to interfere with the pill as well. The most important thing is that you take the pill every day so do what you have to do to make that happen.

Brand versus generic

Thyroid organizations have actually recommended that patients use a brand (such as Synthroid). It is not an issue of quality – Synthroid is not made better than generic levothyroxine. The issue is consistency of dose. If you get the same dose levothyroxine from month to month, but it comes from two different manufacturers, there might be a slight difference in the actual dose you get. This could affect your TSH. This rarely happens so almost all of my patients are okay with generic levothyroxine. The most important thing is that you take the pill the right way. If we are having difficulty keeping some one’s level normal we may try a brand.

What about Amour Thyroid?

Levothyroxine is physiologically natural. What does that mean? Well, it is made in a lab like other medications, but it's actually bio-identical to the T4 molecule that naturally comes out of our glands (except for just one amino aside) so the only effects it has on your body are the same exact effects that natural thyroid hormone has. Therefore there are no side effects or toxicities. If your dose is too high or too low then you may have the natural/physiologic effects of high or low thyroid hormone. Some people are rarely allergic to the coloring they use in the pill. There is something called Armour Thyroid, which many patients claim is more “natural”. This is actually a pig’s thyroid gland desiccated (put in a blender) then made into a pill. I have personally never found that to sound very natural, and the pigs appear to be factory-farmed (not very wholesome). Dessicated pig’s thyroid has a combination of T3 and T4 as well as other thyroid things. The ratio is T3 to T4 is not similar to that found in humans. That being said, there is no compelling medical reason why you cannot take desiccated pig thyroid. If you feel better on Armour Thyroid (or Nature-throid) I certainly would not argue with that, and I would not try to convince you to stop it.

What about T3 Replacement?

Just like T4 is available in a pill they also make T3. It’s called liothyronine (Cytomel is a brand name). Most of the thyroid hormone that comes out of the thyroid gland is in the form of T4. We have an enzyme in our blood and tissues that converts the T4 into T3. If you have hypothyroidism your thyroid gland will be dysfunctional but (presumably) not the enzyme. If you take T4 then your body should know what to do with it. Many patients have reported that they better after T3 was added to the T4. Several small studies, however, were not able to show any beneficial effect. One larger study did show an effect in patients who had an error in a gene for the enzyme. Those patients made up 16% of the total study population. I have therefore remained open-minded to adding T3 in patients who still suspect that their thyroid level is off despite optimal T4 replacement, and I have indeed found many patients do feel better. It is something I therefore try if patients do not feel well on

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