Measuring Thyroid Stimulating Hormone (TSH) is the single best laboratory measure to assess thyroid function, whether low or high. Most clinical laboratories suggest a normal TSH values are between 0.4 mIU/mL and 4.5 mIU/mL. However, the American Association of Clinical Endocrinologists and the College of American Pathologists recommend that normal values are between 0.4 mIU/mL and 3.1 mIU/mL.
Understanding TSH test results is counterintuitive because high values indicate low thyroid function while low values indicate elevated thyroid function.
The major hormone producing glands
A component of the Framingham Study looked at the relationship between thyroid hormone levels measured by Thyroid Stimulating Hormone (TSH) blood tests and the relative risk of developing dementia. It found that ONLY in WOMEN there was a more than two-fold increase in the risk of developing dementia if TSH levels are either below 1.0 mIU/L or greater than 2.1 mIU/L.
Thyroid hormone is important for healthy neurological function. In patients with suspected dementia it is important to rule out thyroid hormone abnormalities. This research provides more evidence that healthy thyroid function may be indicated by TSH levels that are within a narrower range than the the currently accepted reference ranges.
Be well,
Richard