What is adynamic bone disease?
Adynamic bone disease is the most common type of renal osteodystrophy and can lead to fragility fractures. Patients with ESRD who are older, diabetic, and on peritoneal dialysis are most at risk. The pathogenesis is unclear, but excessive suppression of PTH (<100 pg/mL) plays a major role. There is no diagnostic biochemical profile that can establish the diagnosis of adynamic bone disease. Recently, a ratio of 1-84/7-84 PTH of <1 correlated with a bone biopsy showing adynamic bone disease. In addition, a low BSAP level <7 ng/mL with a PTH <100 to 150 pg/mL is suggestive of this disease. Alternatively, an elevated BSAP and/or a PTH level >400 pg/mL makes adynamic bone disease unlikely. However, in most cases a bone biopsy is necessary to establish a definitive diagnosis and will show a markedly reduced bone turnover resulting from lack of osteoblast and osteoclast activity. The suppressed PTH is often a result of excessive use of calcium-based phosphate binders, active vitamin D analogs, use of high calcium dialysate, or cinacalcet. Patients can be asymptomatic or have symptoms such as hypercalcemia and fractures. Treatment is aimed at eliminating PTH suppression to allow the PTH to rise to the recommended level of 150 to 300 pg/mL for patients on dialysis. Bisphosphonates should never be used to treat osteoporosis or fragility fractures in a patient with ESRD without first having a bone biopsy to rule out adynamic bone disease. Interestingly, teriparatide has been used in some patients with success.
