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Thyroid Diseases

Worries About TSH Levels

10/01/2009

Question:

I have a history of Graves. Was on medication until 2 years ago exactly. Have been taking blood tests; ---9 months ago: TSH:0,9 T4;16,3 ---4 months ago: TSH:0,44 T4:16,8 ---Now: TSH:3,68 T3:5,5, T4:16,6

My question is: Should I worry because of the fluctating TSH? Does TSH go through any "typical pattern" before people go either hyper- or hypothyroid? (For an example, like here, first goes down and then climbs up rapidly and then....?)

Thank you

Answer:

The TSH doe fluctuate a little bit due to time of day, pulses of TSH secretion, and the normal responses to slight rises and falls of thyroid hormone levels in the blood stream as their secretion is regulated by TSH. The bottom line is that I wouldn't worry about any TSH that was within normal limits. A TSH near the upper or lower limit of normal might indicate a trend that will eventually result in an abnormal value, or it might just be part of the normal fluctuation of TSH levels. I might repeat a TSH level a little earlier if it were near the upper or lower limit of normal (say, in 3-4 months).

There is no typical pattern that would predict hyper- or hypothyroidism other than a trend toward TSH levels closer and closer to the upper or lower limit of normal. Your level of 0.44 might have made me want to repeat the test earlier than usual, but the return of the TSH to a point well within normal limits indicates that the TSH of 0.44 did not, in fact, predict a trend toward hyperthyroidism.

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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