Blood levels of progesterone may impact blood vessel function

Blood levels of progesterone, a major female sex hormone, may play an important role in modifying vascular function in postmenopausal women, according to a new study accepted for publication in the Journal of Clinical Endocrinology & Metabolism (JCEM).

“Our study shows that in postmenopausal women, higher blood levels of progesterone are associated with less of an increase in blood pressure and less blood vessel constriction in response to angiotensin II, one of the naturally occurring substances in the body which causes the blood vessels to constrict,” said Emily Szmuilowicz, M.D., of Brigham and Women Hospital and lead author of the study. “Constriction of the blood vessels can lead to increased blood pressure, which can contribute to problems such as heart attack and stroke.”

A growing number of studies have shown that differences in blood levels of estrogen, even within the low range of estrogen levels experienced by postmenopausal women, are related to risk of many common diseases such as osteoporosis and breast cancer. This is the first study to suggest that postmenopausal progesterone levels also have physiological importance as they may impact vascular function.

Thirty-four hypertensive, postmenopausal women were included in the study. Serum estradiol, serum progesterone, blood pressure, and renal vascular resistance (RVR) were measured at the beginning of the study, and blood pressure and RVR were measured once again after an infusion of angiotensin II.

Following the angiotensin II infusion, the women had increases in blood pressure and blood vessel constriction. Among postmenopausal women in low-sodium balance, these responses were blunted with increased endogenous progesterone concentrations.

“Our findings highlight the importance of examining the effects of progesterone as well as estrogen in studies of postmenopausal women,” said Szmuilowicz.

A rapid release version of this paper has been published on-line and will appear in the December 2007 issue of JCEM, a publication of The Endocrine Society.

Founded in 1916, The Endocrine Society is the world's oldest, largest, and most active organization devoted to research on hormones, and the clinical practice of endocrinology. Today, The Endocrine Society's membership consists of over 14,000 scientists, physicians, educators, nurses and students in more than 80 countries.