Low
Testosterone and Parkinson's Disease in Males – Emory Researchers
Study the Possibilities of a Common, Unrecognized Comorbidity
Emory University
researchers may have found a common but heretofore unrecognized link
between low testosterone levels and certain non-motor symptoms (fatigue,
depression, anxiety or sexual dysfunction) in male Parkinson's disease
(PD) patients. When given testosterone replacement therapy (TRT), the
researchers report that patients with low levels of testosterone experienced
significant improvement in these symptoms, which had not responded to
other medications. But investigators caution they only looked at a small
group of five patients and they did not compare those people to a placebo
or control group.
Michael Okun, M.D., and Mahlon
DeLong, M.D., in the Department of Neurology, as well as William McDonald,
M.D., in the Department of Psychiatry and Behavioral Sciences will present
their findings at the American Academy of Neurology 54th Annual Meeting
in Denver, Colo., on April 17. The researchers will also publish their
work in an upcoming issue of the Archives of Neurology.
"Testosterone deficiency
affects 20 to 25 percent of males over age 60 in the general population
and it turns out this deficiency may account for some of the non-motor
symptoms seen in PD," says Dr. DeLong. "However, there have been no
prior clinical studies on the effects of testosterone replacement in
male PD patients." Emory researchers reviewed the cases of five male
Parkinson's patients who came to their clinic with unexplained loss
of energy and vitality. These patients were not responsive to anti-parkinsonian
and anti-depressant medications and had no evidence of other conditions
such as hypothyroidism. Researchers screened for testosterone deficiency
with the St. Louis Testosterone Deficiency Questionnaire, a 10-point
validated questionnaire to determine low testosterone levels. Blood
plasma tests to check for low testosterone were also performed. The
five patients then began testosterone replacement.
Okun and colleagues reported
that following treatment, all five patients experienced significant
improvement in refractory, or unresponsive, non-motor symptoms of PD,
especially fatigue, depression, anxiety and decreased libido. Motor
disabilities appeared to improve in several men, but researchers are
unsure whether they improved secondarily as a result of increased energy
or if they were directly affected by the TRT.
To assess the prevalence
of testosterone deficiency in male PD patients, Emory researchers also
analyzed testosterone levels in 68 PD patients enrolled in a Parkinson's
registry at Emory. Researchers discovered 35 percent of male PD patients
in the registry had low testosterone levels. The risk of testosterone
deficiency was found to increase 2.8 fold per decade. These numbers
at least parallel those seen in the general male geriatric population.
Dr. Okun comments, "More
controlled studies are needed to verify the proportion of male PD patients
found to have low testosterone." Further studies will also help determine
whether testosterone deficiency is simply a comorbid condition (a medical
condition that exists in addition to the main diagnosis) or if it may
influence the onset, progression and clinical expression of the disease.
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