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Thyrotropin levels show relation to Alzheimer’s disease in women
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Women with high or low levels of thyrotropin may be at an increased risk of Alzheimer’s disease.
Researchers from Beth Israel Deaconess Medical Center, and other sites in Boston, conducted a trial to determine the link between baseline thyrotropin levels and cognitive performance.
The study included 1,864 euthyroid participants from the Framingham Study. Two-hundred and nine participants (142 women) developed Alzheimer’s disease at a mean follow-up of 12.7 years. Compared with women in the middle tertile for thyrotropin concentration at baseline, those in the low (<1.0 mIU/L) and high (>2.1 mIU/L) tertiles at baseline were at an increased risk for Alzheimer’s disease (P<.001 and P=.003).
In men, the risk for Alzheimer’s disease was not linked to thyrotropin levels.
When the researchers excluded participants prescribed thyroid supplements, the relationship between thyrotropin levels and risk for Alzheimer’s disease did not significantly change. – by Stacey L. Adams
Arch Intern Med. 2008;168:1514-1520.
This is a nicely done observational study linking the incidence of Alzheimer’s disease in the elderly with a single measurement of thyroid-stimulating hormone. Women in the lowest (<1.0 m IU/L) and highest tertiles (>2.1 m IU/L) had an increase in the incidence of Alzheimer’s disease over a mean follow-up duration of approximately 13 years. This did not apply to men and could not be correlated with a host of cardiac risk factors or taking thyroid hormone. These data lend credence to the potential importance of subclinical hypothyroidism and hyperthyroidism on cognitive performance and may suggest that the normal range for TSH, should be narrower than 0.5 mIU/L to 5.0 mIU/L. Several cautionary points must be made. The observation was not maintained if the analyses were limited to those with TSH values from 0.5 mIU/L to 5.0 mIU/L — the standard normal range. Clearly, prospective studies are needed to establish whether achieving a clinically challenging goal of sustaining TSH levels between 1.0 mIU/L and 2.1 mIU/L lessens the incidence of Alzheimer’s disease or if somehow lower and higher tertile TSH levels are sometimes the consequence rather than the cause of Alzheimer’s disease.
– Jeffrey Garber, MD
Endocrine Today Editorial Board member