A few months back in the context of a male contraceptive, I wondered if
the synthetic progesterone used might not cause problems in men similar
to the problems women experience on birth control pills. I also
mustered support for a hypothesis that the artificial progesterone used
in hormone replacement caused these problems by interfering in the
pathway for allopregnanolone synthesis. Here's the first experimental
evidence I've found in support of this.
http://www.sciencedaily.com/releases/2004/06/040608065645.htm
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Source:
Emory University Health Sciences Center
Date:
2004-06-08
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Synthetic Hormone Used In Contraceptives And HRT Produces Negative
Effects In Monkey Studies
ATLANTA -- Medroxyprogesterone acetate (MPA), a synthetic form of the
naturally occurring steroid hormone progesterone widely used in
contraceptives and hormone replacement therapy (HRT), 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 (CBN) 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."
Kim Wallen, PhD, Dobbs Professor of Psychology and Behavioral
Neuroendocrinology at Emory University, also is a study co-author.
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The Yerkes National Primate Research Center of Emory University is one
of eight National Primate Research Centers funded by the National
Institutes of Health. The Yerkes Research Center is a multidisciplinary
research institute recognized as a leader in biomedical and behavioral
studies with nonhuman primates. Yerkes scientists are on the forefront
of developing vaccines for AIDS and malaria, and treatments for cocaine
addiction and Parkinson's disease. Other research programs include
cognitive development and decline, childhood visual defects, organ
transplantation, the behavioral effects of hormone replacement therapy
and social behaviors of primates. Leading researchers located worldwide
seek to collaborate with Yerkes scientists.
The Center for Behavioral Neuroscience, a National Science Foundation
Science and Technology Center consisting of more than 90 neuroscientists
at eight metro Atlanta colleges and universities, conducts research on
the basic neurobiology of complex social behaviors. Its programs have
led to a breakthrough treatment for anxiety-related disorders and new
understanding of the potential roles of the neurochemicals vasopressin
and oxytocin in autism. CBN's workforce training programs also have
contributed significantly to enhancing the diversity of Georgia's
burgeoning biotechnology industry.
Editor's Note: The original news release can be found here.
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This story has been adapted from a news release issued by Emory
University Health Sciences Center.