Research Insights

Beneficial effects of testosterone replacement for the nonmotor symptoms of Parkinson’s disease

Okun, M., Walter, B., McDonald, W., Tenover, J., Green, J., Juncos, J., & DeLong, M. (2002, Nov.) Beneficial effects of testosterone replacement for the nonmotor symptoms of Parkinson’s disease , 59, 1750-1753

This article is similar to the May 2002 article by Okun et. al. However, they expanded the study to include 10 nondemented men with PD (average age 70.8) that had testosterone deficiency. They were asked to apply a testosterone gel to their shoulders, chest, and abdomen daily. In this study, the participants were given measures of motor and nonmotor symptoms, a dyskinesia rating scale, PDQ39, depression and anxiety questionnaires, tests of attention and verbal fluency, and the Epworth Sleepiness Scale. Six of the ten patients were followed up after 3 months (1 patient was lost to follow-up, 2 discontinued the study for unrelated illnesses, and 1 developed congestive heart failure). There was significant improvement in testosterone levels at 1 and 3 months. They also found improvement after 1 month (not at 3 months) in "fluctuations" as measured by the PDQ39 and improvement in Intellectual Functioning/Psychosis as measured by the PDQ39 at 3 months (not found at 1 month). In regards to the cognitive measures, they found improvement in letter fluency (e.g. generating as many words as possible in one minute that begin with a specific letter) at three months (not found at 1 month). They also found that patients showed improvement in anxiety symptoms at the 1 month follow up but not at 3 months. Symptom scores were not presented in this study; consequently, it is unclear if the improvement in anxiety and language are clinically significant even though they are statistically significant. What that means is patients may have reported improvement on 1 or 2 questions, which is statistically significant but 1 or 2 points may not represent a marked improvement for the patient (clinically significant). Additionally these authors used various cut off levels for statistical significance (p<0.05 and 0.1). Typically, studies use a more stringent cut off of p<0.05 for statistical significance. If the more stringent cut off is used, five of the aforementioned results are lost but still suggestive of the reported trends. The authors conclude that this trend suggests that the patients reported improved energy, enjoyment in life, and sex drive. They discuss that a possible reason they did not find more significant results in this study was due to the difficulty in significantly increasing testosterone levels in several patients. They recommend continued research in this area, particularly with regard to better dosages/increased testosterone, as many of the nonmotor symptoms of PD are very similar to those seen in testosterone deficiency.

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