Why Should You Be Concerned About Osteoporosis?

I am 37 years old and have been diagnosed with osteoporosis. My endocrinologist cannot find a reason why. I have had two children naturally, and prior to that I was always getting estrogen via hormonal contraception. Is it possible that this just happens sometimes? I always hear that osteoporosis is this awful thing you don’t want to end up with. How bad is it really and why?

—Anonymous

Osteoporosis before menopause is rare — so rare, in fact, that we don’t often order bone density tests in young women. When I see a premenopausal woman with osteoporosis in my office, the first thing I want to know is why a bone density test was checked to begin with. Often it is because the patient has fractured bones in unexpected ways or with frequency.

The reason osteoporosis is uncommon in premenopausal women is that bone mass is not static. From before birth to about age 30, we build up bone density. From age 30 to menopause, our bone density remains roughly the same. In the first five years after menopause, bone density drops somewhat precipitously, and then it drops more gradually over the rest of our lives.

In premenopausal women, we diagnose osteoporosis when her bone density is less than two standard deviations below that of other women her age. There are two reasons why this can happen. First is that something prevented you from building bone as a child or adolescent so that you did not reach your expected peak bone density. Chronic illness is a common culprit here, especially diseases that can affect how the body absorbs nutrients, such as celiac disease or Crohn’s disease. History of an eating disorder can also lead to decreased peak bone density, especially if it was severe in the teens and 20s, as can relative energy deficiency in sports (RED-S), particularly if a woman has irregular or absent periods.

The second reason a woman can have premenopausal osteoporosis is that something has caused her to lose bone even before her estrogen levels drop in perimenopause. Some medications can cause bone loss, such as steroids, some types of chemotherapy, and some antiseizure medications. Some endocrine disorders can also cause bone loss. Hyperthyroidism, a disease in which the body makes too much thyroid hormone in an unregulated way, can cause bone loss.

Finally, there is a temporary loss of bone during pregnancy and especially with breastfeeding. While bone density does recover after weaning, studies suggest it can take more than 18 months to regain the bone lost during breastfeeding. As a result, if a woman has a low bone density within 18 months of weaning, I will often repeat the test after an additional 12 months to see if bone density levels have improved on their own.

But to your point, why do we worry about osteoporosis? Decreased bone density increases the risk for fractures, in particular spinal compression fractures and hip fractures, which can cause pain and in older adults limit mobility and lead to an overall loss of function. In general, premenopausal women are at lower risk for fractures, but premenopausal women with decreased bone density are more likely to have fractures than those with normal bone density.

However, in the study linked above, experiencing a fracture between the ages of 20 and 50 increased the risk of a postmenopausal fracture by about 75%. Meaning, while your risk of fracture today is still small, if your low bone mass is left unaddressed you would be at a very high risk of fracture later in life, when bone loss may accelerate and when your body may be less able to recover. As a result, the goal of identifying and treating premenopausal osteoporosis is to reduce your risk of fracture later.

The upshot: While premenopausal osteoporosis is rare, it can occur and it significantly increases a woman’s risk for fractures later in life. Identifying the cause of osteoporosis, if there is one, and treating low bone density can reduce the risk of fracture later in life.