NEW YORK (Reuters Health) - The loss of estrogen that accompanies menopause contributes to the development of obesity and high blood pressure (hypertension), according to studies conducted in female rats.

Estrogen is known to protect women against heart disease. When women reach menopause, their estrogen levels drop dramatically and they lose this protection and often put on weight Dr. Lourdes A. Fortepiani of the University of Texas Health Science Center at San Antonio, reported.

The findings were reported by Dr. Fortepiani and her colleague Dr. Huimin Zhang at an American Physiological Society-sponsored meeting held in Austin.

The researchers showed that in older female rats, free of heart disease, estrogen deficiency appears to trigger the development of high blood pressure and obesity.

Rats that had their ovaries removed, thereby depleting their estrogen levels, had significantly higher blood pressure and gained twice as much weight as "control" rats with intact ovaries.

"The increase in blood pressure seems to be related to the increase in body weight," Fortepiani told Reuters Health.

Rats that had their ovaries removed also showed 70-percent higher levels of the fat hormone leptin and 35 percent higher blood sugar levels.

However, treating these "ovariectomized" rats with estrogen abolished these effects. "When you treat with estrogen, the animals don't gain that much weight and their blood pressure goes down," Fortepiani said.

Moreover, female rats without ovaries that receive estrogen replacement therapy do not experience any of these adverse hormonal and metabolic effects, she said.

While acknowledging the controversy surrounding hormone therapy, these findings may open up new therapeutic approaches for postmenopausal hypertension, Fortepiani added.