Scientists Investigate Link Between Estrogen Deficiency and HIV (dateline May 7, 2001)
For years, researchers have been investigating connections between estrogen loss and osteoporosis, heart disease, and other problems. Now, there appears to be a link between estrogen deficiency and HIV, the human immunodeficiency virus that causes AIDS. Although the preliminary results have only come from animal studies, the scientists believe that topical formulas of estrogen may help protect women from HIV infection without the side effects or risks associated with oral estrogen replacement therapy.
Preston A. Marx, Director of the AIDS Research Program at the Tulane Regional Primate Research Center, was working on developing a model of heterosexual HIV transmission when he noted that the vagina undergoes significant physiological changes throughout the female menstrual cycle. Marx noticed that the chances of infection are greater after ovulation when progesterone levels are the highest.
Progesterone is a hormone responsible for preparing the uterus for possible pregnancy and preparing the breasts for lactation (milk production). Estrogen works to regulate a womans monthly menstrual cycle and secondary sexual characteristics (such as breast development and function), and also prepares the body for fertilization and reproduction. Estrogen also provides protection from infections and other problems. Progesterone, on the other hand, blocks estrogen, which helps protect the body from some of estrogens negative effects (such as increased growth of cells lining the uterus). However, according to Marx, high progesterone levels can also block positive effects of estrogen, such as possible protection from HIV.
Marxs initial research involved studying primates (monkeys) with simian immunodeficiency virus (SIV), the primate version of HIV. Marx and his colleagues inoculated 12 monkeys with SIV and then treated some of the monkeys with estrogen or progesterone implants. All six of the untreated monkeys eventually developed SIV. Five out of six (83%) of the monkeys that were treated with progesterone implants also developed SIV. However, none of the six monkeys treated with estrogen implants developed an SIV infection.
The scientists were initially surprised that the estrogen treatment provided 100% protection against SIV in the monkeys. However, some previous research has suggested that women who use progesterone injections as birth control (such as Depo Provera) are at higher than average risk of contracting HIV (see below for more information on HIV).
Because the results of Marxs research showed that estrogen implants were effective at preventing SIV infection (equivalent to HIV in humans), the researchers want to continue their research by testing estrogen creams. Because topical estrogen formulas are not associated with as many side effects and risks as oral estrogen replacement therapy (such as bloating, nausea, breast tenderness, increased breast cancer risk with long-term use, etc.), Marx and his colleagues believe that topical estrogen is the most appropriate form of estrogen to study. Topical estrogen formulas are spread on external female genitalia.
Though the scientists have not yet performed any studies of topical estrogen in women, they believe that their initial animal findings warrant human studies. Marx and his colleagues have recently been awarded a $2 million grant from the U.S. National Institutes of Health. Their first investigations will involve using estrogen cream in primates to determine whether it provides HIV protection. If those studies are successful, tests in women may be on the horizon.
While this research is promising, it is still in very preliminary stages. Women should not assume that estrogen decreases their risk of HIV. HIV attacks the immune system and is believed to cause AIDS (acquired immune deficiency syndrome). HIV can be transmitted by blood, semen, breast milk, and vaginal fluids. HIV is commonly spread by:
- Having unprotected sexual intercourse with a person who has HIV
- Sharing needles or syringes with a person who has HIV
- Receiving transfusions of blood products donated by a person who has HIV
- Getting HIV-infected blood, semen, or vaginal secretions into open wounds or sores
- Being deeply punctured with a needle or surgical instrument contaminated with HIV
- Being passed from a woman to her fetus during pregnancy or birth
- The study, "Estrogen Protects Against Vaginal Transmission of Simian
Immunodeficiency Virus," is published in the September 2000 issue of the Journal
of Infectious Diseases. An abstract of the study is available at http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db
- To learn more about estrogen replacement therapy, please visit
- To learn more about HIV and AIDS, please visit http://www.aids.org/