Generalized osteitis fibrosa may be differentiated from other skeletal dystrophies which are clinically similar. This condition is characterized by a high serum calcium content, low plasma phosphates, increased excretion of calcium in the urine, and negative calcium balance; an adenomatous tumor of one or more parathyroid glands has always been found at postmortem examination and nearly always at operation, while the remaining glands are normal in size and structure.

There is no good evidence that Paget's disease is caused by hyperparathyroidism. In this condition the calcium and inorganic phosphate content of the blood are normal; the calcium balance in the chronic phase of the disease is markedly positive; the output of urinary calcium is greatly decreased; and the parathyroid glands are usually found to be entirely normal in size and in microscopic structure.

Ankylosing polyarthritis is probably not caused by hyperparathyroidism because, in this condition, although the serum calcium may be slightly above normal, the inorganic phosphates of the plasma are normal; the calcium balance is positive; the parathyroid glands have been reported enlarged, but usually this enlargement was symmetrical, involving all of the parathyroids similar to that reported in cases of rickets or low calcium osteomalacia. In experimental animals the addition of vitamin D and of adequate calcium and phosphorus to the diet will result in decrease in size of the enlarged parathyroid glands as well as healing of the skeletal disease.

Parathyroidectomy in cases of ankylosing polyarthritis or of Paget's disease is not a justifiable procedure unless there is more adequate evidence of parathyroid gland pathology than has been presented in reports of cases in the literature.

Demineralization of the skeleton in polyarthritis may be accounted for as atrophy of disuse.