Parathormone is useful in which of the following?
Histologically, patients presented with a broad range of bone turnover abnormalities as determined by activation frequency and bone formation rate/bone surface. 
Results of the five iPTH assays in each patient correlated but were significantly different. 
There were also significant differences between iPTH measurements at the same bone turnover level. Using Kidney Disease Outcome Quality Initiative recommended iPTH ranges, all assays showed comparably poor diagnostic performance. 
At 80% specificity, cut-off values of the 5 iPTH assays for low bone turnover varied from 165 to 550 pg/ml and for high bone turnover from 404 to 1,003 pg/ml. Sensitivities at these cutoffs remained below acceptable standards.
Addition of AP measurements to iPTH did not improve diagnostic accuracy.
Hyperparathyroidism
Paget's disease
Osteoporosis
Osteomalacia