I have asthma and another inflammatory lung condition called Sarcoidosis. I have to take an inhaled and an oral corticosteroid for these two problems. I've had one vertebral compression fracture so far. The doctor tells me I'll always be at risk for other fractures because of the steroids. What's the connection between these medications and bone fractures?

The link between corticosteroids and bone loss leading to osteoporosis and fracture risk is complex. The mechanisms behind bone formation and bone resorption when taking steroids remains complex and are not fully understood.

Lab studies show that patients taking corticosteroids start to have less calcium in their bloodstream. At the same time, there is a disruption in the body's vitamin D activation. The kidneys help keep the right amount of calcium in the body by resorbing some of the calcium from the blood stream. But this is changed, too.

With changes in the amount of available serum calcium and the altered vitamin D, the gastrointestinal (GI) system is unable to absorb calcim needed for bone production. The end-result is a loss of bone mineral density.

Further bone loss occurs when low serum calcium levels lead to hyperparathyroidism. The hyperparathyroidism acts in the body to cause even more bone resorption. Without medical intervention, it can be a vicious cycle.