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When Your Thyroid Levels Are Fluctuating

Risk Factors, Reasons and Solutions for Changes in TSH, T4 and T3 Levels


Updated June 10, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

When Your Thyroid Levels Are Fluctuating

A number of factors can cause thyroid test levels to fluctuate.


Some physicians have concerns about the accuracy of thyroid tests, in particular the TSH test. Richard Shames, M.D., a California-based practitioner who has written a number of books on thyroid disease, feels that the handling of the samples for TSH tests may also result in inaccuracies because:

"...the blood that is drawn in the morning at almost every lab in the U.S. is usually not run through the machinery for analysis until that evening. During that time, your hormones - especially the important TSH - may end up showing lower on your test result than is accurate for you. TSH is also a pituitary hormone that, according to the best standards, should be refrigerated properly once drawn. Most big labs have blood samples couriered to them. Are these kept at exact proper temperature? Hardly ever. TSH serum is rarely refrigerated."

You can read more about Dr. Shames' concerns in this article on Tests for Thyroid Testing and Evaluation.

5. Timing of When and How You Take Your Pill

If you are taking your thyroid medication at different times each day, you may be sometimes taking your thyroid hormone on an empty stomach, and sometimes with or after having food. Taking thyroid hormone with food may delay or reduce the drug's absorption by changing the rate at which it dissolves or by changing the stomach's acid balance. This means that, if you were taking your thyroid hormone on an empty stomach and start taking it with food, you may see a change in your thyroid levels. Similarly, if you were taking it with food and start taking it on an empty stomach, you may see improved absorption and changes in levels.

If you want to ensure the best possible absorption, you'll want to take your thyroid medication first thing the morning, on an empty stomach, about one hour before eating and before drinking coffee. (Coffee can interfere with your medication absorption.) You may want to take your thyroid medication with vitamin C, because studies show that it can improve absorption. Also, make sure to keep at least three to four hours between taking thyroid medication and taking any calcium or iron supplements. (That also goes for calcium-fortified juices.) A high-fiber diet is also a factor. While healthy, quickly going up or down in fiber intake can affect thyroid medication absorption.

You may also wish to talk to your practitioner about taking thyroid medication at night, because several studies have shown improved absorption at nighttime.

>p>But ultimately, consistency is what you should strive for, in terms of how you take your drugs. If you're going to take your thyroid hormone with food, take it every day with food, consistently. Don't take it some days with food, some days without, or you're likelier to have erratic absorption, and it may be harder to regulate your thyroid levels.


And if you plan to change the way you take your thyroid medication, make sure you clear it with your practitioner first; be sure to get retested again no more than six to eight weeks after you've settled into your new pattern, to see if you need a dosage adjustment.

6. Eating Too Many Goitrogenic Foods

Certain foods can have what's known as a goitrogenic effect, or the ability to enlarge the thyroid and make it form a goiter. These foods can act like antithyroid drugs in slowing down and disabling the thyroid, ultimately causing -- or worsening existing -- hypothyroidism. If you still have a thyroid, you need to be more concerned about not over consuming these goitrogens in their raw form.


What foods are goitrogenic? Brussels sprouts, soy, rutabaga, turnips, kohlrabi, radishes, cauliflower, African cassava, millet, babassu (a palm-tree coconut fruit popular in Brazil and Africa) cabbage and kale are all considered goitrogenic. Some experts believe that the enzymes involved in the formation of goitrogenic materials in plants can be destroyed by cooking, so thorough cooking may minimize some goitrogenic potential.

7. Change of Seasons

Many thyroid patients aren't aware that thyroid levels, and TSH in particular, can change along with the seasons. TSH naturally rises somewhat during colder months and drops back down in the warmest months. Some doctors adjust for this by prescribing slightly increased dosages during colder months and reducing dosage during warm periods. Most, however, are not aware of these seasonal changes, leaving patients increasingly hypothyroid during cold months or going through warmer months more hyperthyroid. This seasonal fluctuation can be more pronounced in older people, particularly those living in cold climates.

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