Endocrine Abstracts

Osteoporosis management increased determination of serum calcium (Ca) levels, and detection of hypercalcemia in the set of out patients. Serum phosphate (P) levels are less frequently measured in osteometabolic patients. Primary hyperparathyroidism (PHPT) is the most common cause of hypophosphatemia. However, hypophosphatemia receives poor attention during the PHPT diagnostic work up, and also data in literature are scanty. We retrospectively reviewed the clinical records from 3 different series of PHPT patients: a first surgical series (group 1; all patients underwent successful parathyroidectomy), a second series from a Hospital setting with Emergency Department (group 2), and a third series of out-patients referred for osteoporosis management (group 3). In group 1, serum P levels were measured in 74 [13%; 13 males, 61 females; 58.0 (49.0,67.3) years, median (range IQ)] out 567 surgically confirmed PHPT patients, confirming that it is often neglected. Group 2 included 115 PHPT patients, 22 males, 93 females, aged 65.5 (56.0, 74.0) years. Group 3, included 88 PHPT patients, 13 males, 75 females, aged 66.0 (59.0, 75.0) years. Group 1 patients were younger than those in group 2 (P=0.003) and group 3 (P=0.0005 by ANOVA). Serum phosphate levels were lower in Group 1 patients [2.4 (2.1, 2.8) mg/dl] with respect to levels in Group 2 [2.7 (2.3, 3.0) mg/dl, P=0.016] and group 3 [2.7 (2.4, 3.0) mg/dl, P=009 by ANOVA] patients. Considering the whole series of 277 patients, hypophosphatemia (<3.0 mg/dl) was detected in 209 (75%) patients. Serum P levels were lower in males than females. Hypophosphatemia was mild (2.1–3.0 mg/dl) in 171 patients (62%), moderate (2.0–1.1 mg/dl) in 37 (13%), while severe hypophosphatemia (<1.0 mg/dl) was not registered in any patients. As expected, hypophosphatemic PHPT patients showed lower serum total calcium, higher PTH levels, than normophosphatemic patients. Any difference in age, serum creatinine levels, ionized calcium levels, serum 25hydroxyvitamin D (25OHD), 24 h urine calcium excretion corrected for body weight, prevalence of kidney stones, bone mineral density at lumbar and femur sites as well as number of fragility fractures could be detected. Indeed, a positive correlation emerged between serum 25OHD and P levels (r=0.176, P=0.015 by Spearman correlation). In conclusions, our data supported recently published data on hypophosphatemia in PHPT patients, confirming the relationship with a more severe PHPT phenotype. Determination of serum P levels concomitantly with serum calcium, PTH, 25OHD, and creatinine helps clinicians in the diagnosis of PHPT and in estimation of its severity.