Normocalcemic primary hyperparathyroidism in clinical practice: an indolent condition or a silent threat?

OBJECTIVE: To describe the characteristics of normocalcemic primary hyperparathyroidism (NPHPT) in patients seen for osteoporosis evaluation. PATIENTS AND METHODS: We examined the records of 156 women who came to the hospital to be screened for osteoporosis. Measurements of total calcium, PTH, 25-hydroxy vitamin D, and β-C-telopeptide were recorded. Bone mineral density and T-scores were evaluated by densitometry of the lumbar spine, femoral neck and distal one-third of the radius. The latter was only measured in patients with primary hyperparathyroidism. Nephrolithiasis and bone fractures were documented by a review of the medical records. RESULTS: We identified 14 patients with NPHPT, accounting for 8.9% of the population studied. In the medical records, the occurrence of kidney stones was reported in 28.6% of the patients with NPHPT, in contrast with only 0.7% of the noncarriers. Regarding the presence of general fractures, 21.4% of the patients with NPHPT were affected versus 16.2% of noncarriers. CONCLUSION: Data from our study suggest that NPHPT has a diverse phenotypic presentation, implying that this may not be an "indolent" disease.