MON-541 Successful Treatment of Normocalcemic Hyperparathyroidism in Children

Childhood and adolescence are the critical periods for the establishment of lifelong bone health. Normocalcemic primary hyperparathyroidism (NPHPT) has been recognized as a variant of primary hyperparathyroidism (PHPT) 15 years ago and it is characterized by elevated PTH level with persistently normal concentrations of albumin-adjusted total and ionized calcium, in the absence of secondary causes of hyperparathyroidism and it is related to increased risk in development of osteopenia or osteoporosis as well as development of parathyroid adenoma and hypercalcemia-hypercalciuria with renal consequences. In order to identify biochemical disorders of PTH in normocalcemic children we performed in all patients that visited our pediatric endocrine unit for two years (1-Nov 2016 until 31-Oct 2018), a complete calcium metabolism evaluation (Ca, P, ALP, 25OHD, intact PTH). A total of 3060 patients - excluding those that consulted for vitamin D deficiency, Ca metabolism abnormalities or known renal pathology (i.e. Bartter syndrome) - were included. We identified 157 patients (5.1%) with hyperparathyroidism (PTH > 45 pg/ml, Horm Res Paediatr 2015;84:124-129) and normal total serum calcium levels; adequate data on laboratory results and follow up were available in 114 patients; 67 (58.7%) of them were vitamin D replete (25OHVitD >30 ng/ml, group 1) and forty-seven were vitamin D deficient (41.3 %) (25OHVitD <30 ng/ml, group 2). All patients were treated with cholecalciferol (8000-16000 IU daily). All patients in groups 1 and 2 who did not normalize their PTH (< 45 pg/ml) within 6 months of monotherapy with vitamin D, received additional calcium supplementation (1000 mg/day). Evaluation of calcium metabolism (Ca, P, ALP, 25OHD, 1,25OHD, PTH) was performed every 3 months. In 6 patients (4 from group 1 and 2 from group 2) elevated PTH did not respond to 6 months of combined cholecalciferol/calcium therapy. These patients were switched to the non-calcemic synthetic 1-25(OH)2-vitamin D analogue, paricalcitol, at the dose of 2 mcg x 1-3/day. Evaluation of calcium metabolism (Ca, P, ALP, 25OHD, 1,25OHD, PTH, urine Ca/Cr) was performed every 3 months. Parathormone levels normalized in 5 patients by 3 months of treatment and in one by 10 months of treatment with calcium in serum and urine being within normal range for age during treatment in all patients. We propose that all normocalcemic children that are checked for vitamin D deficiency undergo concomitant measurement of PTH levels. Subclinical hyperparathyroidism (PTH > 45 pg/ml) should be treated with cholecalciferol (8000-16000 IU/day) and calcium supplementation (1000 mg/day) and if unresponsive after a minimum of 3 months, with paricalcitol 2-6 mcg/day in order to normalize PTH and protect their bone and general health. Further studies are needed to standardize this approach.