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Thyroid Diseases

Fluctuating TSH Results and Birth Control Pills



I have a question regarding hyperthyroidism and birth control. I was born w/o a thyroid or it is inactive and have been taking Synthroid all my life. The amount is usually .125-.150.

In February 2006 I went off of birth control after being on it for 10+ years. Since then my thyroid TSH results have fluctuated (.100-.150, .100 the lowest I have ever been). I usually get my blood tested every 6 months, my TSH will be off. Then test again in a month, TSH is fine. Test again 6 months later and it will be off. Test in a month and it is fine again.

I would like to know if coming off birth control can change my thyroid hormones? If so how long does it take to get "normal" again? Also, having hypothyroidism, will it affect me getting pregnant? And will my menstraul cycle have an affect on my TSH results?

When I try to talk to my doctor, the only advice she can give me is that the thyroid is hard to duplicate and they try with meds. The hormone changes every day so it is hard to diagnose. Do you agree w/ this?

Could you provide me with a site/book that has extensive information about the thyroid and its effects?

Thanks for you help!


Going off birth control pills might require a one time reduction in your thyroid hormone dose. It might take as long as four months to be sure that the effect of stopping the birth control pills has completely disappeared. After that, however, there is no reason why having been on birth control pills should cause your thyroid hormone requirements to fluctuate this much.

TSH levels of 0.1 to 0.15 are all too low. However, this looks suspiciously like a set of thyroid hormone doses. Are these really your TSH results, or are they your doses of thyroid hormone?

One problem might possibly be trying to repeat the thyroid blood tests a little too soon. Usually I wait 2 months to recheck the blood test if I am increasing the dose of thyroid hormone, and 3 months if I am decreasing the dose of thyroid hormone. Other things you can do to keep your requirement from fluctuating so much are...

1. Take the pill every day first thing in the morning with water, but not with any food or any other pills, including vitamins, minerals, calcium, iron, or anything else. Food and other pills may be taken an hour later.

2. If you forget a pill in the morning you may take it whenever you remember it. If you miss an entire day you may take 2 pills the next day. Note: this is not true for all pills, just thyroid hormone.

3. Be sure the pharmacist isn't changing brands on you at every refill. It doesn't matter which brand you use, but stick with one brand from refill to refill.

As long as you are on a dose of thyroid hormone that gives you a normal TSH, your hypothyroidism should not affect your ability to get pregnant. Once you get pregnant, it is important to follow the TSH levels closely because your thyroid dose may need to be adjusted. Your menstrual cycle should not affect your thyroid hormone dose requirement.

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Response by:

Thomas A Murphy, MD, FACP, FACE Thomas A Murphy, MD, FACP, FACE
Associate Professor of Medicine
School of Medicine
Case Western Reserve University