FHH vs Normo-hormonal PHPT

Familial hypocalciuric hypercalcemia and normohormonal primary hyperparathyroidism present significant diagnostic overlap, both manifesting with hypercalcemia alongside inappropriately non-suppressed or normal intact parathyroid hormone levels. Differentiating these entities hinges on accurate assessment of renal calcium handling. Calculating the 24-hour urinary calcium-to-creatinine clearance ratio remains the standard initial screening tool, where a ratio below 0.01 strongly suggests familial hypocalciuric hypercalcemia, whereas a ratio above 0.02 favors primary hyperparathyroidism.