Background: Hormone levels change significantly with increasing age. These changes may be related to, or be associated with, the emergence of age-related diseases, such as Alzheimer's disease (AD).
Methods: Five hundred and seventy-six women over the age of 65 were studied from the Washington Heights-Inwood Columbia Aging Project (WHICAP). These women were selected from a group of healthy Medicare beneficiaries that were aged 65 and older living in the geographically defined area of northern Manhattan in New York City. Serum levels of estrone (E1), estradiol (E2), total testosterone (TT), dehydroepiandosterone (DHEA), luteinizing hormone (LH), follicle stimulating hormone (FSH), and sex-hormone binding globulin (SHBG) were measured.
Results: Significant differences were found between patients with AD and controls only in the level of SHBG, which was 20% higher in patients compared to controls (68.5nmol/l versus 54.7nmol/l, P<0.001). We also estimated levels of total E2 because after menopause, E2 is largely derived from E1. AD patients had significantly lower levels of estimated E2 (AD 0.46 versus controls 0.49, P<0.01). Differences remained significant after adjusting for age, ethnic group, education, and body mass index (BMI).
Conclusions: A marked increase in SHBG levels was found in AD patients. SHBG normally responds to circulating testosterone and estrogen, therefore, elevated SHBG suggests an abnormal increase in its production and regulation. Further work is needed to clarify the cause and consequences of this observation.