Our bones provide the scaffolding that holds our bodies upright. Contrary to popular belief, healthy bones are not solid. Their interiors are made of a honeycomb structure with tiny holes to keep them light and springy. 

However, bones that have lost a lot of mineral density have much larger holes as well as thin outer walls, which can increase their risk of breaking. So bone density is important.

Age and lifestyle can lower bone density and increase risk for conditions such as osteoporosis (dangerously low bone density) and osteopenia, which is not as extreme as osteoporosis. Low bone density is a widespread problem: Each year an estimated 1.5 million individuals suffer a fracture due to bone disease.

At Yale Medicine, our endocrinologists specialize in metabolic bone disease. These are conditions caused by deficiencies in minerals such as calcium, phosphorus, magnesium or vitamin D or problems with the hormones that regulate our blood minerals. Sometimes metabolic bone disease can be due to problems in the proteins and chemicals that make up the bones themselves. “With our depth of knowledge and reputation as a major referral center, we’ve seen the whole spectrum of cases,” says Karl Insogna, MD, director of the Yale Medicine Bone Center.

Low bone density can lead to serious medical conditions that could result in bone fractures.

The most worrisome condition is osteoporosis, where low bone density causes holes inside the bone to widen and the outer walls of the bone (the cortex) to thin. This causes the bone to be more fragile. 

People with osteoporosis are at a much greater risk for fracture with little or no trauma. For example, an older person can get a hip fracture as a result of a simple fall from a standing position. Hip fractures are the most serious of all osteoporotic fractures and can cause loss of mobility and independence and even death.

Osteopenia is similar to osteoporosis but where the bone density is not as low.  People with osteopenia are at increased risk for developing osteoporosis.

The following can lead to bone loss and an increased risk of fracture:

• Smoking
• Drinking excessive amounts of alcohol
• Low physical activity
• Poor diet, low in vitamins and calcium
• Changes in hormones (from smoking or menopause)
• Age
• Medical conditions like rheumatoid arthritis, chronic kidney disease, overactive parathyroid gland or celiac sprue
• Certain medications like glucocorticoids or hormone blockers
• Multiple myeloma—a cancer that causes bone to weaken and fracture easily

Early warning signs of low bone density are subtle. A stooped back or decreasing height can be a sign of decreasing bone density in your spine. A loss of two inches or more of height may indicate that you have osteoporosis. 

If you experience stress fractures in your feet with normal activity or fracture a rib with no particular trauma, you should ask a doctor to check for osteoporosis or osteopenia. If you suffer an arm, wrist or a hip fracture with a fall from a standing position, you are very likely to have fragile bones and definitely need a bone density test.

Doctors use X-rays to measure bone mineral density (BMD) and check for your risk of  developing osteopenia or osteoporosis. Your BMD number will be compared to the BMD number of healthy, young, adult individuals of the same sex, and, in some cases, the same racial background. If your BMD is 2.5 units lower than that reference number, you have osteoporosis. If your BMD is between 1 and 2.5 units lower than the standard BMD, then you have osteopenia.

Although there is no cure for osteoporosis or osteopenia, there are ways doctors can help slow bone loss and sometimes improve bone density. Most commonly, doctors will recommend that patients supplement their vitamin D and calcium intake. Doctors may also prescribe medications like bisphosphonates or denosumab, which slow bone breakdown. 

Estrogen supplements for post-menopausal women can slow bone breakdown and are effective at relieving other menopausal symptoms. However, estrogen can have side effects, including a higher risk for breast cancer, blood clots and heart disease.

The doctors at the Yale Medicine Bone Center specialize in hard-to-diagnose cases. We offer a wide range of diagnostic tools that not only measure bone density, but other biochemical measures such as vitamin D levels.

Much of our diagnosis is done in-house at the Yale Medicine Mineral Metabolism Lab.

The physicians in the Yale Medicine Bone Center are recognized nationally and internationally for their expertise in osteoporosis and metabolic bone disease. Dr. Insogna is on the Board of Trustees of the National Osteoporosis Foundation.

To make a diagnosis, our doctors work across departments and disciplines. “We often put our heads together and recognize that what we're seeing is not necessarily run-of the-mill and, therefore, requires something more than a run-of-the-mill treatment,” says Dr. Insogna.

In addition, patients at the Yale Medicine Bone Center get access to treatments through clinical trials that are not yet available to the wider public.