Let's take a look at some of the issues behind the question.
First, by sublingual, we're referring to taking a thyroid pill and either crushing it and placing it under the tongue, or allowing it to dissolve.
Second, the question about sublingual use of thyroid medications is always related to natural desiccated thyroid (NDT) drugs like Armour, Nature-Throid or Erfa thyroid. That is because these drugs include the thyroid hormone T3 -- which is faster-acting and has a far shorter-half life than the synthetic T4 found in levothyroxine drugs like Synthroid, Levoxyl, and Eltroxin. Some people feel the effects of T3 very quickly, even within an hour or two, but a levothyroxine drug typically takes much longer to be converted into the T3 that is ultimately usable by the body.
Third, the argument that is made for taking thyroid medication sublingually is that by doing so, the thyroid medication is absorbed through the mucous membranes in the mouth, and goes straight to the bloodstream, which prevents the medication absorption from being affected by things like calcium supplements, iron supplements, food, coffee, or fiber -- which are all known to inhibit thyroid medication absorption.
To explore the issue further, Geri Rybacki, Executive Director of the Coalition for Better Thyroid Care and I both talked to a variety of doctors, drug companies and other experts, to get a sense of the professional perspective on the issue.
The consensus? The active ingredients in thyroid medication have molecules that are so large that it is difficult for them to pass through the mucous membranes. Most of the dissolved/crushed medication ends up swallowed, and moves through the digestive system in the usual way. Other factors also affect sublingual absorption, including oral pH, and salivary enzymes.
Thyroid expert Kenneth Woliner, MD in Boca Raton, Florida said that some medications are designed to be taken sublingually -- for example, drugs that need to be fast-acting, and when where seconds count (like nitroglycerine, used to treat angina and heart attacks) -- and have a molecular structure that lends itself to sublingual absorption. But thyroid is not one of them, according to Dr. Woliner.
Thyroid expert Kent Holtorf, MD, founder of the National Academy of Hypothyroidism, and the Holtorf Medical Center network of clinics in California and the Midwest, also agrees that thyroid medication was not designed for sublingual use, therefore the size of the thyroid hormone molecule means that sublingual use of thyroid medication may not be optimal for some patients as far as absorption, and may not prevent interactions that can reduce absorption of thyroid medications.
We also contacted several natural thyroid drug manufacturers, and while they all refused to go on the record publically, they concurred that they felt that sublingual administration of natural desiccated thyroid does not prevent other substances -- like iron, calcium, fiber, coffee -- from impairing absorption.
Still, a small subset of thyroid patients report anecdotally that they (1) feel better when taking NDT sublingually (2) are able to take their thyroid medications sublingually, along with coffee, breakfast, or supplements with iron and calcium, and still maintain good thyroid function or (3) feel better and have improved TSH, Free T4 and Free T3 levels when taking their thyroid medication sublingually. What could be going on?
Since there have not been any studies to evaluate the effectiveness of the sublingual route for natural thyroid, we can only speculate that perhaps these patients may have some sort of digestive malfunction, i.e. rapid digestion, which means that the pill may not even be fully dissolved before it leaves the stomach and goes into the intestines, or the insufficient enzymes to dissolve and digest the pill. By crushing/dissolving the pill in the mouth, perhaps this is allowing the pill to break down and begin to be digested.
It would be interesting to see a research study done to compare the two methods of taking natural desiccated thyroid -- sublingually versus swallowed -- evaluating the effectiveness of each method as far as TSH, Free T4, Free T3 levels, qualify of life and symptoms. An ideal study would also look at subgroups of patients swallowing their medication orally, vs. sublingual who, (1) drink coffee at the time of their medication, (2) take iron supplements at the time they take their medication, (3) take calcium supplements at the same time, and (4) eat at the same time as their medication.
(Don't hold your breath waiting for this research to be funded or performed, however. Few studies are ever done on natural thyroid drugs, or thyroid patient quality of life.)
In any case, while we're waiting for information, keep in mind that if you do decide to take your NDT sublingually you should:
- discuss this with your physician first, before making any changes
- keep track of your symptoms carefully
- have your thyroid levels carefully evaluated 6 to 8 weeks later -- including TSH, Free T4, Free T3, and ideally, also Reverse T3