What TSH Level Constitutes Hyperthyroidism?

[tourmax]

Hi Doc ~
I'm having hyperthyroid symtoms such as heat intolerance, fatigue, exercise induced tachycardia, weight loss, and irritability. However, my TSH level is 1.75 which is at the lower end of the normal range.

Is it possible to get get symptoms of hyperthyroidism when my TSH level (1.75) is within the lab reference range, but at the low end of the range?

Because of the tachycardia my cardiologist is doing a series of tests including an "Event Monitor" which I'm wearing right now to capture any electrical disturbances or other heart disease.  He suspects (IST) inappropriate sinus tachycardia of possible thyroid orgin.

I'm 67 years old. My PCP currently has me on 150 mcr of Synthroid for hypothyroidism, but in the last 6 months I definitely have developed hyperthyroid symptoms.

I would greatly appreciate your thoughts!

[tourmax]

Dr. Lupo & GravesGirl --

Many thanks for your quick reply!!

[Mark Lupo, M.D.]

The TSH is completely normal but would look at prior TSH levels as some individuals may be sensitive and do better with TSH in the higher normal range.  Lowering the synthroid dose would be one consideration to discuss with your doctor to see if it has any impact on the tachycardia but the TSH suggests it should not.

[GravesGirl]

you may need a dose reduction now. You need a free t 3 and free t 4 test done to see where your thyroid hormones are at.You maybe over medicated and it's giving you hyper symptoms.

[tourmax]

Correct T-4 = 1.20, not 120.  Sorry for another typo! :-(

[tourmax]

Hi Dr. Lupo ~

In my original post I mistakenly indicated an incorrect TSH level of 1.75. I apologize for the error!  With only very minor deviations my thyroid lab results for the past 18 months are as follows:  TSH = 0.01, and
T-4 = 120.  

Is my current dosage of 150 mcg of Synthroid excessive? I'm working with my PCP and cardiologist to reduce the current 150 mcg of Synthroid due to tachycardia and other hyper symptoms (weight loss, heat intolerance, fatigue, irritability).  What would you suggest as my targets for TSH, T4 and Synthroid dose?  Could you recommend an Endocrinologist in Tampa?

Thanx again!!