Diabetes & The Body

Osteoporosis: Getting To The Bone

Osteoporosis is a bone condition characterized by low bone mass, increased fragility, decreased bone quality, and an increased risk for bone fracture. Both low bone mass conditions increase fracture risks, with osteoporosis having the greater impact.

Although, it has been historically reported mostly in white women, it does affect people of both sexes and all ethnic groups. Osteoporosis is not symptomatic until there is a fracture. It is now known that persons with either type1 or type2 diabetes are among those people at an increased risk for this disease.

The technological wonder called dual X-ray absorptiometry (DXA) is used to study bone mass. This test is not the perfect diagnostic tool because there are many micro-architectural bone qualities and bone geometries that are not detectable with DXA. Therefore, a comprehensive risk assessment for osteoporosis should reach beyond bone mineral density measurements. This is particularly true when assessing people with diabetes. Type1 diabetes has long been associated with low bone density.

The mechanism of bone loss in type1 diabetes is still unknown but there are theories based on animal and cellular models. Insulin-like growth factors and other cytokines may influence diabetic bone metabolism. Diabetic retinopathy, advanced cortical cataracts, and diabetic neuropathy have all been associated with increased fractures. Due to the fact that type 1 diabetes has a young age of onset when bone mass is being accrued, low bone mass would seem to be a likely complication for type 1 diabetes.

Type 2 diabetes had previously been thought to provide bone protection because it is associated with normal to increased BMD, but this information was not based on prospective controlled large trials. Risk factors are higher for type 2 diabetics than for the general population because of peripheral neuropathy, possible hypoglycemia, nocturia, and visual impairment. Because many type 2 diabetics are over weight and sedentary, coordination and balance factors that protect people from falls are impaired or not present.

Thus patients with a larger body size and relatively high bone mass may have a higher fracture rate. Bone quality changes may also be affected by microvascular events common to diabetes. Studies have confirmed that women with type 2 diabetes experience higher fracture rates in regions of the hip, humerus, and foot than do nondiabetic women. Bone loss has also been observed to be greater in patients with poorly controlled diabetes than in those whose diabetes was in tight control.

Gestational diabetes has not been reported to be associated with bone loss in prospective trials. However, a small study involving Hispanic women with gestational diabetes noted that 40% of the 20 enrolled subjects had CXA-detected bone loss when 3 months postpartum. Advanced age and higher oral glucose tolerance test values during pregnancy may be associated with increased bone loss. Larger prospective studies are needed to confirm these findings.

Prevention of osteoporosis requires recognition of populations who are at risk, plus screening programs targeting these populations. None of the available tests addresses all of the issues involved in disease assessment. In addition to screening, attempts should be made to address all potentially modifiable risk factors. Additionally patients at high risk should be advised to wear hip protectors that have been reported to reduce the risk of hip fractures by 60%.

Treatment includes calcium and Vitamin D. Exercise can also have clinical benefits. In addition to improvements in bone mass, it also results in improved overall muscle strength, which is important in preventing falls. The exercise program should be designed to help not do damage. For example, people who have vertebral osteoporosis should avoid back flexion exercises, particularly those with weights, because they can increase fractures.

Hormone replacement therapy (HRT) was long thought to be the best treatment for osteoporosis because it improved BMD at the hip and spine by 5% and 2.5% respectively. However, we all know that the use of HRT has come under question and the FDA removed approval of estrogen for treatment of osteoporosis, but did permit estrogen to maintain its indication for the prevention of osteoporosis. In type 2 diabetic women, combination HRT is limited to low-dose formulations. In men, androgen replacement has improved BMD, however it cannot be used in men with a history of prostate cancer.