The diagnosis of hyperparathyroidism is not difficult in full-blown cases, but in the obscure or atypical case requires the aid of multiple laboratory tests. Most of these, however, provide only indirect evidence. The recent development of a radioimmunoassay for circulating parathyroid hormone eliminates this disadvantage, but the procedure is too complicated for use in the ordinary clinical laboratory. Thus, it would appear that for some time to come most physicians will have to depend upon indirect methods for the differential diagnosis of hypercalcemia and specifically for the evaluation of parathyroid function.
Among the characteristics of hyperparathyroidism subject to chemical testing are failure of urinary hydroxyproline to decrease following calcium infusion, increased calcium turnover rates, failure of serum calcium levels to fall with glucocorticoid treatment, and inability of parathyroid extract administration to increase urinary phosphate excretion.
Since none of these indicators is infallible and some may be conflicting, in difficult cases