SYNTHETIC HORMONE USED IN CONTRACEPTIVES & HRT PRODUCES NEGATIVE EFFECTS IN MONKEY STUDIES

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SYNTHETIC HORMONE USED IN CONTRACEPTIVES & HRT PRODUCES NEGATIVE EFFECTS IN MONKEY STUDIES
24 February 2007 - Emory University

Medroxyprogesterone acetate, a synthetic form of the naturally occurring steroid hormone progesterone widely used in contraceptives and hormone replacement therapy, increases aggression and anxiety and reduces sexual activity in female monkeys, according to a study published in the June edition of The Journal of Clinical Endocrinology and Metabolism.

The investigators, from the Yerkes National Primate Research Center of Emory University and the Center for Behavioral Neuroscience in Atlanta, say the findings may explain anecdotal reports of mood changes, depression and loss of libido in some women who use MPA for contraception and HRT.

In the counter balanced-designed study, Yerkes and CBN post-doctoral fellow Karen Pazol, PhD, compared aggression, anxiety and sexual behavior in six female pigtail macaques that received one week each of three different treatments: estrogen only, estrogen plus natural progesterone, and estrogen plus MPA.

Monkeys displayed significantly more aggressive and anxious behaviors when they received the estrogen/MPA combination as compared to when they received the estrogen only or the estrogen/progesterone combination. Dr. Pazol also noted a marked reduction in sexual activity during the estrogen/MPA treatment period.

"Our findings suggest MPA may be affecting certain neuroendocrine systems in a very different way than natural progesterone," explained Dr. Pazol. "In comparison to natural progesterone, MPA binds to glucocorticoid receptors with a much higher affinity and may have a greater impact on the brain's stress system."

Moreover, according to Dr. Pazol, unlike natural progesterone, MPA cannot be converted to the mood-regulating chemical, allopregnanolone. Changes in allopregnanolone levels have been associated with depression, anxiety disorders and premenstrual mood disorders in humans.

To identify MPA's behavioral effects over a longer period, Dr. Pazol also is examining aggression, anxiety and sexual activity in monkeys that receive the estrogen/MPA regimen for 21 days, the standard cycle for women who take contraceptives.

"Dr. Pazol's Yerkes-based animal studies provide a critical link to better understanding of HRT and its behavioral-related effects," says Mark Wilson, PhD, a study co-author and chief of Yerkes' Psychobiology Division. "Few reliable clinical studies of MPA's behavioral effects have been conducted because of the variability in hormone levels among women and the subjective nature of reports on mood and libido."

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About: Emory University
Emory University is home to nine major academic divisions, numerous centres for advanced study, and a host of prestigious affiliated institutions. In addition to Emory College, the University encompasses a graduate school of arts and sciences; professional schools of medicine, theology, law, nursing, public health, and business; and Oxford College, a two-year undergraduate division on the original campus of Emory in Oxford, Ga.

Emory was founded at Oxford by the Methodist Church in 1836. Led by President James W. Wagner, an award-winning teacher and scholar, the University has 11,300 students and 2,500 faculty members who represent all regions of the United States and more than 100 foreign nations.

Emory University is known for its demanding academics, outstanding undergraduate college of arts and sciences, highly ranked professional schools and state-of-the-art research facilities. For more than a decade Emory has been named one of the country's top 25 national universities by U.S. News & World Report. In addition to its nine schools, the university encompasses The Carter Center, Yerkes National Primate Research Center and Emory Healthcare, a comprehensive metropolitan health care system.

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