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

To describe the characteristics of normocalcemic primary hyperparathyroidism (NPHPT) in patients seen for osteoporosis evaluation.

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.

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.

Data from our study suggest that NPHPT has a diverse phenotypic presentation, implying that this may not be an "indolent" disease.