NEW YORK (Reuters Health) - Testosterone deficiency appears to be associated with increased apathy that is common among men with Parkinson's disease, results of a pilot study suggest.

Previous research has shown that testosterone administration to male subjects facilitates functions that are subserved by the prefrontal cortex, lead author Dr. Rebecca E. Ready and her associates explain in the September Journal of Neurology, Neurosurgery and Psychiatry. Furthermore, apathy is linked to frontal systems dysfunction, and frontal systems dysfunction has been implicated in Parkinson's disease.

To investigate the possible link between low testosterone levels and apathy, the group, based at Brown Medical School of the University of Pittsburgh, enrolled 49 non-demented men with Parkinson's disease. Patients as well as spouses or other informants who knew the patients very well completed the Frontal Systems Behavior Scale (FrSBe). Blood samples were drawn for measurement of testosterone levels.

The authors found that 23 had low total testosterone, defined as 325 ng/dL or less. Self-reported apathy on the FrSBe was inversely related to free testosterone levels (p < 0.05). The results were similar when informants completed the FrSBe, and after controlling for disease severity.

"If future studies corroborate our findings that testosterone deficiency is associated with symptoms of apathy, then testosterone replacement therapy should be considered as a potential treatment for apathy in men with Parkinson's disease," Dr. Ready and her colleagues maintain.

However, until a prospective, placebo-controlled trial is completed, they add, clinicians should not treat testosterone deficiency in patients with Parkinson's disease.

In an editorial commentary, Dr. S. F. Farmer suggests, "the idea that dopamine and testosterone deficiencies act as comorbidities - which combine in susceptible patients to reduce frontal lobe system functioning leading to reduced libido, sexual dysfunction, fatigue, mood change, and apathy - is important."

The ability to treat significant non-motor symptoms of Parkinson's disease will be welcomed, adds Dr. Farmer, a physician at National Hospital for Neurology and Neurosurgery in London.

J Neurol Neurosurg Psychiatry 2004;75:1323-1326

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