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MALE HORMONE LINKED TO HYPERTENSION IN MEN
Castrated male rats had kidney function as good as female rats in a study at the University of Mississippi Medical Center (UMC) leading the scientist to link the male hormone tetosterone to the increased rate of high blood pressure and kidney disease in older males.
Dr. Jane Reckelhoff, associate professor of physiology and biophysics at UMC, says men, as they age, suffer from high blood pressure and kidney disease more than women.
A man's kidney ages much more rapidly than a woman's, she notes. By age 80, a man loses 45 percent of kidney function, whereas a woman, by the same age, only loses about 30 percent of kidney function. Men also have slightly higher blood pressures than women. The problem could be abnormal sodium handling in male kidneys, and Reckelhoff is looking at gender differences in this mechanism.
Reckelhoff's studies focus on the effect of testosterone on sodium handling. One particular hormone, angiotensin, can affect sodium reabsorption in the kidney. Reckelhoff wants to know if testosterone increases the amount of angiotensin, and thereby increases sodium reabsorption which leads to high blood pressure and kidney disease.
Now it is just a matter of verifying that testosterone is, indeed, the problem. To test her theory, Reckelhoff used a study group of five types of rats: normal males, castrated males, normal females, females with their ovaries removed, and females with their ovaries removed that had been given testosterone. Twice weekly, Reckelhoff checked the blood pressure and kidney condition of the rats and after 12 weeks, she noted several findings.
The kidneys of the normal females and the females without ovaries aged slowly and remained healthy. ( Because females without ovaries do not produce the female hormone, estrogen, this study suggests that it is not estrogen that keeps the kidney healthy). The kidneys of the castrated males also aged slowly and were markedly healthier like the females. The kidneys of the normal males, however, progressively became worse with age. Reckelhoff noted that the kidneys of the fifth group, females without ovaries that were given testosterone, were comparable to the normal males in all respects.
Reckelhoff said, "The two study groups with testosterone show a progressive loss of kidney function over time. This suggests that testosterone is the problem. If we can prove testosterone contributes to high blood pressure and kidney disease in men, we can start administering the proper medication to men to treat the problem."
Reckelhoff added, "For example, if dihydrotestosterone, one type of testosterone, is found to be the problem hormone, then a medication already on the market for prostate reduction could be an effective treatment."
Reckelhoff's work is described in the January, 1998, issue of the journal, Hypertension.
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