Kennedy's disease is a hereditary disease where men have a mutation on their X chromosome. They have large breasts, a low sperm count, difficulty speaking and swallowing, and weak muscles in their legs and arms. Studies have been conducted to see whether men with this disorder have more muscle strength after taking testosterone.
Definition
Kennedy's disease is also referred to as X-linked spinobulbar muscular atrophy. X-linked means it is a hereditary disease that usually only affects males. The term "spinobulbar muscular atrophy" describes the degeneration of the nerves in the spine and bulbar area of the brain. It results in the wasting away and weakness of the muscles in the arms and legs, and in the bulbar muscles that affect speech and swallowing, writes Robert Brown, Jr., M.D., Professor of Neurology at Harvard Medical School in "Harrison's Principles of Internal Medicine."
Development of Disease
The disease develops because there is a mutation on the X chromosome in the gene that makes the androgen receptor, as explained by Allan Ropper, M.D., Executive Vice Chair of Neurology at Brigham and Women's Hospital in "Adams & Victor's Principles of Neurology." Receptors are proteins inside of a cell or on a cell membrane that do what they are told. The androgen male hormone attaches to the androgen receptors and gives instructions to the cell. Scientists have found androgen receptors on the nerves of the spinal cord.
Symptoms
Dr. Ropper writes in "Adams & Victor's Principles of Neurology" that the symptoms usually start when people are in their 30s. The disease may affect the shoulder and hip muscles first, with them becoming weak and wasting away. People may have muscle cramps and twitching. Approximately 50 percent of the people with Kennedy's disease have problems with their bulbar muscles and have a hard time speaking and swallowing. They may even have twitching and weakness on the face, which is clearly visible. Most men have gynecomastia, or enlarged breasts, and a low sperm count.
Evaluation
Michael Rubin, M.D., Director of the Neuromuscular Service and EMG Lab at New York Presbyterian Hospital writes about the evaluation in "The Merck Manual for Healthcare Professionals." It includes a test called an electromyogram, or EMG, that makes a graph of the electrical currents made in a muscle. A nerve conduction velocity study checks on the speed of the signals sent by the nerves. The levels of creatine kinase, a protein that is released when the muscles are damaged, can be increased. Genetic testing can be done and it will show the mutation.
Testosterone
Testosterone is a male hormone, or androgen, and men with Kennedy's disease have low testosterone levels and low muscle strength. The National Center for Research Resources conducted a clinical trial to see if taking testosterone increased the muscle strength in men with this disorder. The study results have not been released. However, in the October 2008 issue of the Journal of Neurology, Neurosurgery and Psychiatry, Professor Guy Rouleau writes about a study where a 6- year-old man with this disease did much worse after taking testosterone, but returned to his previous level after stopping the therapy.
References
- "Adams & Victor's Principles of Neurology"; Allan Ropper, M.D., Martin Samuels, M.D.; 2009
- "Harrison's Principles of Internal Medicine"; Anthony Fauci, M.D., Dennis Kasper, M.D., Dan Longo, M.D. et al.; 2008
- "Journal of Neurology, Neurosurgery and Psychiatry"; Administration of testosterone results in reversible deterioration in Kennedy's disease; Guy Rouleau; October 2008
- The Merck Manual for Healthcare Professionals: Spinal Muscular Atrophies
