Thirty cases of concurrent Paget's disease and primary hyperparathyroidism: Sex distribution, histomorphometry, and prediction of the skeletal response to parathyroidectomy

Studies of the effect of parathyroidectomy (PTX) on bone turnover in patien ts with the combination of primary hyperparathyroidism (PHPT) and Paget's d isease (PD) are largely limited to case reports. The etiology of the: combi nation is disputed. We report 30 patients and their biochemical (n = 17) an d histomorphometric (n = 4) responses to PTX in 18. All 18 patients except one had a post-PTX fall in plasma alkaline phosphatase (pAP). There was a s ignificant positive correlation between the degree of post-PTX fall in pAP and both the preoperative plasma total corrected calcium (CaC) (P < 0.01) a nd serum ionized cal cium (P < 0.05). For the patients with CaC levels >3.0 mmol/liter, the mean % fall in pAP was 68% of pretreatment (to 32%). For t hose with CaC levels greater than or equal to 2.68 mmol/liter the fall in p AP was >18%. Of 12 literature cases treated by PTX and followed up, 11 had a postoperative fall in pAP (range 6-83%). Pretreatment bone biopsies (n = 6) could not be distinguished from uncomplicated PD. No significant histomo rphometric changes were documented postoperatively in the four patients stu died; however, % fibrotic surfaces declined in each of the four. Of the 18 patients, only one had radiologic subperiosteal erosions preoperatively; no ne had clinical tetany postoperatively-thus distinguishing this combination of diseases from severe PHPT bone disease-a situation easily biochemically confused with this combination. The sex distribution of 2.75:1 F/M in this series resembles reported ratios in pure PHPT of 2.37:1, unlike the ratios found in pure PD (0.49-1.01:1). The prevalence of PHPT in PD is 2.2-6.0% ( mean 4.4%) in 1836 patients. In our series, 73% of patients with both disea ses were females >60 years of age. In population studies >60 years, PHPT wa s present in 3% of women and 1% of men. Hypercalcemia in PD is frequently a ttributed to immobilization. As part of this study, we examined 184 patient s referred with PD for the existence of, and cause of hypercalcemia. Of thi s group, 21 were hypercalcemic, 19 (90%) of whom had PHPT; none had immobil ization hypercalcemia. In patients with both disorders, the indications for PTX should include the potential post-PTX improvement in pagetic biochemis try and symptoms. The sex distribution (resembling pure PHPT) and the simil ar prevalence of PHPT in Paget's, and in the elderly population, support th e likelihood, in most cases, that these two common diseases are associated by chance.