Premature ovarian failure (POF) affects roughly one percent of women. For reasons not yet known, women who experience this condition cease to menstruate and become infertile. They also cease to produce the female hormone estrogen and the tiny amounts of the male hormone testosterone that women normally produce. The hormone estrogen helps to conserve calcium and other minerals in bone and protects women against bone loss. After women enter menopause and cease producing estrogen, their risk for the bone weakening known as osteoporosis increases.
Briefly, the NICHD researchers found that two thirds of these young women with POF had experienced bone loss to such a degree that they might be at increased risk of hip fracture. Older, normally menopausal women with this amount of bone loss have a three-fold increase in their risk of fracturing a hip, a serious complication of low bone density. The bone loss occurred in these young women despite the fact that most of the women had taken some form of estrogen replacement therapy to alleviate their menopausal symptoms and in an attempt to prevent the loss of bone density.
For the study, the NICHD researchers recruited 89 women with POF. All of these women were 40 years of age or younger, and had previously gone 4 months without menstruating. Women whose ovarian failure was due to a genetic condition or caused by radiation, chemotherapy, or removal of the ovaries were excluded from the study. The average age of the women in the study was 32. To measure the bone mineral density of the POF patients, the researchers employed a technique known as dual photon absorptiometry.
Of the 89 young women studied, 77 had a bone density that qualifies as osteopenia, meaning a bone density below normal. Another 2 young women had bone mineral densities in the hip that qualify as having osteoporosis. The remaining 10 women had bone mineral densities in the normal range for their age.
In addition, bone loss seems to occur rapidly in women with this condition. Roughly 50 percent of the patients had their bone mineral density measured within a year and a half after having been diagnosed with POF. Almost half of these women had osteopenia.
The researchers theorize that this bone loss could have a variety of causes. For example, current regimens to replace estrogen have been designed for post menopausal women and could, perhaps, be insufficient for women with premature ovarian failure, who are under age 40. These regimens do not include the male hormone testosterone, which also protects against bone loss. Many of the POF patients also stopped taking their replacement hormones, for fear of increasing their risk of breast cancer.
In their article, the researchers stated that POF patients' fear of breast cancer resulting from hormone therapy may be unfounded.
"Postmenopausal women are prolonging their exposure to estrogen effect beyond the normal age range," they wrote. "In contrast, women with premature ovarian failure take estrogen to replace what their ovary should be making normally."
The study authors advised physicians treating women with POF to counsel their patients about the need to stay on their hormonal regimens; to exercise, which strengthens bones; and to make sure they consume enough calcium. The National Institutes of Health recommends that girls and young women aged 11 to 24 consume 800 to 1,200 mg of calcium per day--the equivalent of 4 or 5 glasses of low fat milk a day. Between 25 and 50 years of age, premenopausal women who are otherwise healthy should consume 1,000 mg of calcium a day. Otherwise healthy postmenopausal women on estrogren therapy should have 1,000 mg of calcium, and healthy postmenopausal women who are not taking estrogen should have 1500 mg of calcium a day.
According to the study's senior author, Lawrence Nelson, MD, of NICHD's Section on Women's Health, the research team next plans to test whether a patch that supplies small amounts of testosterone--in addition to therapy with replacement estrogen--will prevent bone loss in POF patients.