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Thyroid Diseases

Is the High End of Normal Really Normal?

11/12/2009

Question:

After seeing my doctor for unexplained weight gain (my BMI has climbed to 30), tiredness, and migraines, I was prescribed metformin for insulin resistance/potential PCOS. This has brought my fasting insulin down moderately, but has not assisted with the weight despite restricted carbohydrate and calorie intake. Although my fasting insulin has fallen, it is still not ideal, and my blood tests now show numbers at the top end of the normal ranges for other areas (TSH 3.0, Cortisol 22 (at 9:00 am), Fasting Insulin is 6.4 uIU/ML on max dose metformin) and my Dr. has referred me to an endo (though I`ve seen one about a year ago who told my thyroid and cortisol numbers were normal). Also- my DHEA-s is 140 (down from 240 the year prior)and I showed TPOAb 25 IU/mL a year ago.

Each of these levels is technically in the "normal" range - but does the combination of higher-than-ideal numbers mean something could be off?

Answer:

The TSH is fine - I don't think medications to alter your thyroid function will help you with your weight. Excess cortisol, a condition referred to as "Cushing's syndrome," can cause weight problems but usually causes other problems too, such as weakness in the hips and shoulders and deep, wide, red stretch marks. A single cortisol level cannot be used to test for Cushing's syndrome because the hormone is secreted in pulses. The endocrinologist will be able to tell you if it will be useful to test you for Cushing's syndrome, and will be able to discuss the available tests with you. The fasting insulin level simply tells us that you still have some degree of insulin resistance - if you are overweight, then this doesn't tell us any new information.

All in all, I don't think these normal test results have any hidden meaning in them beyond what your doctor has already discussed with you.

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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