Familial Hypocalciuric Hypercalcemia Types 1 and 3 and Primary Hyperparathyroidism: Similarities and Differences.

Context: Familial hypocalciuric hypercalcemia (FHH) is a genetically heterogeneous condition resembling primary hyperparathyroidism (PHPT) but not curable by surgery; FHH types 1, 2, and 3 are due to loss-of-function mutations of the CASR, GNA11, or AP2S1 genes, respectively.

Objective: This study aimed to compare the phenotypes of patients with genetically proven FHH types 1 or 3 or PHPT.

Design, Setting, And Patients: This was a mutation analysis in a large cohort, a cross-sectional comparison of 52 patients with FHH type 1, 22 patients with FHH type 3, 60 with PHPT, and 24 normal adults.