Prevalence of primary hyperparathyroidism among patients with low bone mass

Accelerated rate of bone turnover and increased resorption due to primary hyperparathyroidism (PHPT) result in osteopenia and an increase in the fracture risk. However, there are no data about the relative frequency of the PHPT in the subpopulation with the low bone mass. The aim of the study was to evaluate the diagnostic power of the bone densitometry in diagnosis of PHPT.

Material consisted of 4016 new patients: 2504 women and 1512 men. Bone mineral density (BMD) in the L2 - L4 vertebra and femoral neck was measured by DEXA (LUNAR - DPX or LUNAR - EXPERT, Lunar Radiation Corp., USA). All the patients with BMD Z-score below -2.0 SD (according to the sex and age) were the subjects of further diagnostic procedures. The serum calcium and intact PTH level as well as 24-hours urine excretion was measured.

In 451 (331 women and 120 men) out of the total 4016 patients, the measured BMD Z-scores were below -2.0 SD. Out of these 451 patients, 52 were diagnosed with PHPT. In 41 patients, diagnosis of PHPT was based on elevated serum intact PTH in the face of overt hypercalcemia. The remaining 11 normocalcemic patients with elevated PTH and coexisting vitamin D deficiency, will become hypercalcemic after vitamin D replacement.

In the large cohort of unselected patients who presented for bone densitometry, a very high (11.5%) prevalence of PHPT was found among subjects with low bone mass (BMD Z-score less than -2.0 SD). Presented results confirm the importance of the BMD measurements in the screening of the disease.