Testosterone deficiency and apathy in Parkinson’s disease: a pilot study
Journal of Neurology, Neurosurgery, and Psychiatry
Ready, R., Friedman, J., Grace, J., & Fernandez, H. (2004) Testosterone deficiency and apathy in Parkinson’s disease: a pilot study Journal of Neurology, Neurosurgery, and Psychiatry, 75, 1323-1326
These authors hypothesize that apathy in PD is related to testosterone deficiency. They suggest that PD is linked to frontal systems dysfunction (frontal lobes of the brain) and that frontal dysfunction has been linked to apathy. They also cite literature from animal and human studies that found when testosterone is administered subjects have been found to have improved abilities that are mediated by the frontal systems. They looked at a pilot study of 49 nondemented patients with PD (avg. age 68.9, education 15.2 yrs) and 40 informants that knew the patients. They found 46% of the sample had low testosterone levels (it is notable that Okun, as mentioned above, used a more sensitive measure, and at this point, there is no generally accepted level to define testosterone deficiency) and that they had a higher mean score on a frontal systems questionnaire (FRSBE) as compared to their non-PD age and education matched normative groups. The majority of patients reported minimal depressive symptoms and that depression scores were moderately correlated with the apathy scale. Although there was a significant correlation, only 9% of the variance (discrepancy or variability) was shared, suggesting the two measures were identifying unique constructs (ideas or entities). They also found that there was a significant inverse relationship between self and informant reported apathy and testosterone levels. Even when the authors accounted for disease severity the relationship remained significant. They also found that patient self report of low energy was associated with testosterone levels. They conclude that testosterone deficiency may account for some of the depressive symptoms seen in PD (e.g. low energy) and that apathy was seen in patients with low levels of testosterone. They address some limitations of their study, including not controlling for the time of day blood levels were drawn and other comorbid medical conditions, medications, or tobacco or drug use, which can all cause a drop in testosterone levels. Additionally, they were limited by the lack of a gold standard to define testosterone deficiency. However, they do suggest that future research needs to look at the relationship between apathy, depression, and testosterone deficiency in patients with PD.