| The purpose of this research study was to investigate whether level of habitual dietary calcium intake (DCI) was associated with differences in bone mineral density (BMD) and biochemical parameters in primary hyperparathyroidism (PHPT). Restricted DCI is often advised to prevent worsening of hypercalcemia and/or hypercalciuria yet, low-calcium diets may lead to increased bone resorption. In contrast, high-calcium diets may suppress parathyroid hormone (PTH) in some patients, but may also elevate urinary calcium, thereby increasing the risk of nephrolithiasis.;DCI was determined from 4-day diet records in 71 patients (55 women, age 56 $pm$ 1; 16 men, age 53 $pm$ 5) with PHPT. Mean DCI was analyzed by group: Low (LCD): 199 $pm$ 14; Moderate (MCD): 529 $pm$ 21; High (HCD): 1023 $pm$ 73 (p =.0001). Results show no influence of DCI on BMD or on the odds of nephrolithiasis. Biochemical indices do not differ significantly between DCI groups, although serum calcium, 1,25-dihydroxyvitamin D (1,25(OH)$sb2$D), and urinary calcium excretion tend to be higher, while mid-molecule and IRMA PTH tend to be lower in HCD.;Patients with elevated levels of 1,25(OH)$sb2$D (76 $pm$ 3 vs 43 $pm$ 2; p =.0001) have higher IRMA PTH (136 $pm$ 11 vs 97 $pm$ 10; p =.0052), urinary calcium (297 $pm$ 19 vs 205 $pm$ 20; p =.0114) and urinary calcium/g creatinine (293 $pm$ 15 vs 198 $pm$ 15; p =.0031) than patients with normal levels of 1,25(OH)$sb2$D, despite similar DCI and BMD. However, patients with elevated levels of 1,25(OH)$sb2$D are not more predisposed to nephrolithiasis than patients with normal levels of 1,25(OH)$sb2$D.;In summary, BMD and biochemical indices do not differ significantly by DCI in a group of patients with mild PHPT, although trends in biochemical indices which parallel responses of healthy individuals to low- and high-calcium diets are apparent. The responses are blunted in PHPT. These new observations provide evidence that dietary calcium need not be severely restricted in PHPT. Patients with elevated levels of 1,25(OH)$sb2$D hyperabsorb dietary calcium thus, in this subgroup, moderate DCI and careful monitoring are recommended. |
