High Blood Pressure :: Estrogen deficiency can lead to obesity-induced high blood pressure after menopause

At menopause, women lose hormone protection against heart (cardiovascular) and kidney (renal) diseases, and are likely to become obese. A research team has tested the idea that estrogen deficiency in aged females may trigger the development of high blood pressure and obesity. The results of their study, using an animal model, suggest that estrogen depletion can have these effects.

The study is entitled, “Role of Estrogens in Postmenopausal Obesity and Hypertension.” It was conducted by Lourdes A. Fortepiani and Huimin Zhang, University of Texas Health Science Center at San Antonio (UTHSCSA), San Antonio, TX.

The team will discuss its findings as part of the upcoming conference, Sex and Gender in Cardiovascular-Renal Physiology and Pathophysiology, being held August 9-12, 2007 at the Hyatt Regency Austin on Town Lake in Austin, TX. The event is the second scientific gathering to be sponsored by the American Physiological Society (APS; www.The-APS.org) this year.

To test their theory the researchers used 24 aged female rats. The ovaries were removed from two-thirds of the group (ovariectomized; ovx) while the ovaries of the other third of the group remained intact and served as controls. The researchers subdivided the ovx rats, giving half of the ovx group estrogen while the other half remained estrogen depleted.

Among the ovx rats, those that did not receive estrogen had significantly higher blood pressure than the control rats (126.2 versus 110.6 mmHg). The rats receiving estrogen had the lowest blood pressure levels of all (102.6 mmHg).

The researchers also noted that the rats which had their ovaries removed and did not receive estrogen compared to the intact rats:

gained twice as much weight as the controls
increased their leptin level by 70 percent
increased their blood glucose level by 35 percent
increased RAS and renal SNS by 16 and 39 percent
experienced no change in kidney function

All the hormonal and metabolic effects were completely abolished with estrogen replacement. In other words, the rats whose ovaries were removed and received estrogen replacement did not undergo any of the changes mentioned above.

With increased life expectancy, women spend more than a third of their life in menopause. In addition, obesity is increasing dramatically in all populations and is a major cardiovascular risk factor in women after menopause. Despite the controversial data about estrogen therapy in clinical studies, the results of this study performed in aged rats suggest that the loss of estrogens after menopause may contribute to the development of obesity and hypertension, opening new therapeutic approaches to postmenopausal hypertension.

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