Osteoporosis is, in the simplest terms, a condition characterized by loss of bone strength, with decreased bone mineral density.
The problem with osteoporosis is that it represents a fracture risk. In other words, when you have osteoporosis you feel no pain or other symptoms, but your bones can break with less energy and less force than someone who does not have osteoporosis. Most troublesome are fractures of the "hip," but fractures at the wrist, back, and shoulder are also common.
Osteoporosis is different from osteomalacia, and other "weak bone" disorders such as osteogenesis imperfecta, etc.
In practical terms osteoporosis is defined by a T-score of less than -2.5. A T-score is a score that is produced by a "DEXA scan" machine.
A T-score between -2.5 and -1.0 means that your bones are weak, but you don't quite make it into the category of osteoporosis according to the World Health Organization. Instead, the label that applies to your bones is "osteopenia."
And finally, a T-score above -1 means your bone mineral density is not too far off from the bone density of a healthy 30-year-old adult.
It turns out that not every patient who breaks a bone has osteoporosis. In fact, the majority of old patients who break a hip do not have osteoporosis as defined above. In statistical speak, less than 50% of the variation in bone strength has been attributed to variations in mineral density. And improvement of bone mineral density with medications accounts for only a small part of the reduction in the risk of fractures. In other words, bone mineral density, T-scores, and so on do not do a very good job of predicting who will break a bone.
So if you are worried about osteoporosis, a better question would be "Am I at risk for breaking bones?"
In addition to the T-score, age is an important predictor of the risk of these so-called "fragility fractures." Sex, race, height, weight, history of prior fractures, use of tobacco, alcohol, certain medications, certain medical conditions, all influence the risk of another fracture in your future.
Dr John Kanis, at Sheffield University in the UK has thought these things over and has come up with something called "FRAX risk assessment tool." Given the appropriate data, FRAX calculates your 10-year fracture risk. You can give it a try here.
If you have been diagnosed with osteoporosis, multiple treatment options exist. As a surgeon, I always ask my patients to stay active and mobile, and that goes a long way towards having strong and healthy bones. Nevertheless, drugs are often beneficial.
According to the US National Osteoporosis Foundation, treatment with medications should be considered in the following circumstances:
The main drug category are the bisphosphonates, such as actonel or fosamax. There is some controversy regarding the use of bisphosphonates due to a certain predisposition for subtrochanteric fractures of the femur. Bisphosphonates work by inhibiting bone turnover. Nevertheless, in certain patients the benefits of bisphosphonates outweigh the risks. Other alternatives exist, such as hormone replacement for women, teriparatide, or denosumab (prolia).
Vitamin D and calcium supplements may be used as well, and at appropriate doses have few side effects. I recommend checking a vitamin D and calcium level prior to starting these medications. A typical dose would be 800 units of Vitamin D and 3 Tums tablets each day.
Last, and least, "bone turnover markers," things such as TRAP, pyridinolines, N-telopeptide of collagen cross-links (NTX), C-telopeptide of collagen cross-links (CTX), could in the future be measured and used to predict fracture risks but at the moment most hospital labs don't measure such things.