Irregular Periods Linked to Bone Loss
Menstrual irregularities are not usually taken seriously by women or doctors. But such disruptions could lead to bone loss--and eventual osteoporosis, researchers have found.
While many people think that bone loss occurs after menopause, when the ovaries have stopped working due to age, researchers now believe that disruption of the ovaries’ function at any age has a direct effect on bones.
Lengthy menstrual cycle disruptions may even serve as a predictor for who will develop osteoporosis later in life.
“The menstrual cycle doesn’t get the respect that it deserves,” says Dr. Lawrence M. Nelson, lead author of a study published in the May issue of the Journal of Obstetrics and Gynecology. “The ovary doesn’t get respect as a gland that makes hormones. Most women think of the ovary as a reproductive gland. But the ovary helps keep your bones healthy.”
A growing body of evidence suggests that the absence of a regular menstrual cycle for three months or longer--a condition called amenorrhea--should be evaluated by a physician in order to address the underlying cause of the condition and to prevent bone loss, Nelson says.
“If you haven’t had a period for three months, you should have it checked out,” says Nelson, a researcher at the National Institute of Child Health and Human Development’s unit on gynecologic endocrinology. “Bone density is like your bank account. You have to keep your bones healthy when you’re young to keep them healthy in their older years.”
Bone is built in childhood and adolescence and remains stable until the late 30s or early 40s.
Bone mass then gradually declines, with the most losses in women occurring during the years just after menopause.
About 10 million Americans have osteoporosis, which is when bone becomes so porous that the risk of fracture is high.
In the study, Nelson and his colleagues studied 48 women, ages 18 to 40, with a condition called premature ovarian failure.
The disorder occurs when the ovaries stop producing eggs and reproductive hormones well in advance of natural menopause.
They found that even when amenorrhea was present, often neither the women nor their doctors expressed concern over the menstrual disruptions.
“Ninety percent of these women were college graduates, and one-third of them had graduate degrees,” says Nelson. “But over half of them did not view missing menstrual periods as an important health issue.”
Some of the women experienced five years of menstrual irregularities and saw at least three doctors before premature ovarian failure was diagnosed.
“If no one figures out your ovaries aren’t working right for five years, you can be losing bone density over that time,” he says.
No one knows how much bone loss can occur with menstrual irregularities or if that bone loss can be replenished.
Previous studies have shown young women with anorexia nervosa have a higher risk of bone fracture.
And an earlier NICHD study of 89 women with premature ovarian failure found that 67% of the women already had signs of osteopenia, a low bone-density condition that precedes osteoporosis.
Although menstrual irregularities are often present, many women with premature ovarian failure, which affects about 1% of women, discover they have the condition only when they seek treatment for infertility.
“It’s a more significant social issue now that women are delaying their childbearing,” Nelson says. “If you are delaying childbearing to age 35, ovarian failure at age 30 is a big problem.”
Premature ovarian failure is not the only condition that causes a shortage of hormones produced by the ovaries, thereby affecting bone health.
Young women can develop amenorrhea because of eating disorders, excessive exercise or stress and pituitary gland tumors.
Whatever the cause, the loss of hormones appears to significantly affect bones--perhaps by interrupting the bone-building process that occurs in the first two to three decades of life, Nelson says.
“Less than optimal development of bone density during adolescence and young adulthood is as important as later bone loss in the development of osteoporosis,” the authors state.
Inadequate hormone levels could cause other problems as well, says Diana Taylor, an associate professor of nursing at UC San Francisco and a member of the Society for Menstrual Cycle Research.
“There are estrogen receptors throughout the body,” she says. “So the loss of estrogen not only affects bones, it could affect other physiological and psychological systems.”
The new study, says Taylor, is further evidence that “we need to help women learn to keep track of their menstrual cycle, and train doctors and nurses to monitor it as part of the health exam.”
Adolescent girls often have irregular menstrual cycles for a year or two after starting their periods.
But after that initial year or two, any disruptions of three months or longer is not normal, Nelson says.
About 3% of young women experience amenorrhea each year. Some of the conditions linked to amenorrhea can be treated to restore normal ovarian function, or replacement hormones can be given to prevent bone loss.
“We’re on a campaign to get the menstrual cycle recognized as a vital sign,” Nelson says. “Women should be asked, ‘When was your last menstrual period, and are your periods regular?’”