Cholecalciferol is almost twice as potent as ergocalciferol in increasing serum 25(OH)D, when administered either by mouth or im. 25(OH)D plays a role in modulating serum PTH.

Primary hyperparathyroidism (PHPT) is a common endocrine disease that is associated with multiple endocrine neoplasia type 1 (MEN1) in ;2% of PHPT cases. Lack of a family history and other specific expressions may lead to underestimated MEN1 prevalence in PHPT. The aim of this study was to identify clinical or biochemical features predictive of MEN1 and to compare the severity of the disease in MEN1-related versus sporadic PHPT (sPHPT). We performed a 36-mo cross-sectional observational study in three tertiary referral centers on an outpatient basis on 469 consecutive patients with sporadic PHPT and 64 with MEN1-related PHPT. Serum calcium, phosphate, PTH, 25(OH)D 3 , and creatinine clearance were measured, and ultrasound examination of the urinary tract/urography was performed in all patients. In 432 patients, BMD was measured at the lumbar spine (LS) and femoral neck (FN). MEN1 patients showed lower BMD Z-scores at the LS (21.33 ± 1.23 versus 20.74 ± 1.4, p = 0.008) and FN (21.13 ± 0.96 versus 20.6 ± 1.07, p = 0.002) and lower phosphate (2.38 ± 0.52 versus 2.56 ± 0.45 mg/dl, p = 0.003) and PTH (113.8 ± 69.5 versus 173.7 ± 135 pg/ml, p = 0.001) levels than sPHPT patients. Considering probands only, the presence of MEN1 was more frequently associated with PTH values in the normal range (OR, 3.01; 95% CI, 1.07-8.50; p = 0.037) and younger age (OR, 1.61; 95% CI, 1.28-2.02; p = 0.0001). A combination of PTH values in the normal range plus age <50 yr was strongly associated with MEN1 presence (OR, 13.51; 95% CI, 3.62-50.00; p = 0.0001). In conclusion, MEN1-related PHPT patients show more severe bone but similar kidney involvement despite a milder biochemical presentation compared with their sPHPT counterparts. Normal PTH levels and young age are associated with MEN1 presence.

Subclinical hypercortisolism may be more common than is generally recognized in patients with osteoporosis in whom secondary causes of osteoporosis have been excluded.

Our data indicate that the CASR SRQ haplotype is significantly associated with PHPT in our population. Within the PHPT patient population, the AGQ haplotype is significantly associated with kidney stones.