Testosterone and Thyroid Stimulating Hormone Levels in Alzheimer's Disease and Their Relationship to Cognition

Previous research suggests that low levels of testosterone may be associated with the development of Alzheimer’s disease (AD). Furthermore, research indicates that low levels of testosterone may be associated with poorer performance on certain neuropsychological tests, as well as increased risk of depression. Evidence also suggests that low levels of Thyroid Stimulating Hormone (TSH) may be associated with AD and with impairments on neuropsychological tests. Thyroid dysfunction has also been linked to depression. For the testosterone analyses, this study utilized data from 61 healthy older men and 68 men with probable AD. Results of ANCOVA indicated that testosterone levels did not differ between the two groups. Regression analyses revealed that testosterone levels did not significantly predict performance on neuropsychological tests or on a measure of depression among AD men. However, testosterone marginally significantly predicted performance on a test of delayed memory, with higher levels of testosterone associated with a higher score. Among controls, testosterone levels predicted estimated premorbid VIQ as measured by a test of word reading. Testosterone was also found to marginally significantly predict performance on a test of verbal fluency, with higher levels of testosterone associated with better performance. For the TSH analyses, data were utilized from 198 healthy elderly controls and 197 probable AD patients. ANCOVA revealed that the groups’ TSH levels did not differ significantly. Regression results indicated that TSH levels did not predict performance on any neuropsychological tests in the AD patients, but within the control group, TSH levels predicted performance on a test of word reading. Additional analyses revealed no association between levels of TSH and testosterone in men. Findings suggest that testosterone and TSH are not associated meaningfully with most neuropsychological test performances in AD patients.