College of Physicians and Surgeons Columbia University New York, NY
C. Bandeira and D. Voss
Hospital dos Servidores do Estado and
F. Bandeira
U. Pernambuco %Recife, Pernambuco, Brazil
Minisola, Rosso and Romagnoli call attention (in their letter above) to their published experience in patients with primary hyperparathyroidism who benefited from surgery with a marked gain in bone mass. They point out, as we have, impressive increases in bone mass. We apologize for omitting their experience in our discussion. Several points, however, are noteworthy.
Our paper was meant to illustrate a remarkable capacity of the skeleton to restore itself in severe osteitis fibrosa cystica. The two cases in our report demonstrate almost unprecedented reductions in T-scores preoperatively of -8.13 and -4.55 and complete recoveries to T-scores of +0.70 and +0.10 respectively. The patients reported by Minosola were not evaluated in a way that is easily comparable. No T-scores were given, but it is likely that a small subgroup of six patients with mean Z-scores of -3.53 probably had substantially lower T-scores. Also, Minisola et al. did not specifically report how much improvement occurred in the subgroup of patients with such Z-scores. Their report merely gives a general impression that they recovered more because the extent of recovery was related to the preoperative Z-score. Only one appears to have improved by more than 3 Z-score units.
Finally, in neither of their papers do Minisola et al. provide data on cortical bone mass, which is the site typically most involved in primary hyperparathyroidism. This makes it difficult for them to speculate on why cancellous bone might improve more readily than cortical bone. Nevertheless, we agree that the explanations for increases in bone mass at cancellous sites are likely to be explained, in part, by mechanical forces as well as in the younger, 17-yr-old patient we reported, by the fact that she was still in the formative phase of peak bone mass acquisition. Undoubtedly, also, the marked increase at cancellous sites is due, as we also point out, to the inherent, greater rate of bone remodeling at cancellous versus cortical sites and the consequent greater rapidity of restoration at sites of greater turnover dynamics.
Footnotes
Address correspondence to: John P. Bilezikian, Department of Medicine, Columbia University College of Physicians and Surgeons, 630 W. 168th Street, PH 8 West, New York City, New York 10032.
Received July 6, 1998.
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