Hypoparathyroidism (HPT) is characterised by hypocalcaemia and impaired renal phosphate excretion and calcium conservation. Oral calcium supplements and calcitriol can improve serum calcium levels but lack the physiologic effects of PTH on renal reabsorption of calcium. RACE is an ongoing open-label study evaluating the long-term safety of recombinant human parathyroid hormone 1-84 (rhPTH[1-84], parathyroid hormone rDNA) in adults with HPT (NCT01297309). In this interim analysis, we report the 3-year treatment effect with 25100 μg/day rhPTH(1-84) on 24-h urinary calcium levels, with or without thiazide diuretics. All data are presented as mean (SD). The study cohort comprised 49 patients enrolled at 12 USA centres; 38 (78%) completed 36 months of rhPTH(1-84) treatment. Baseline demographics were as follows: 82% women, age 48 (9.8) years, HPT duration of 16 (12.5) years, 100% taking prescribed calcium supplements and calcitriol. In response to rhPTH(1-84), albumin-corrected serum calcium remained within the target range over the 3 years; 2.1 (0.17) mmol/l at baseline (i.e., start of rhPTH[1-84], n=49) and Month 36 (n=36). Treatment with rhPTH(1-84) also led to a reduction in urinary calcium, from baseline 8.9 (5.0) mmol/24 h to 6.5 (2.8) mmol/24 h (n=35; P<0.05). Urinary calcium excretion at Month 36 was similar for men compared with women, and in patients taking or not taking thiazide diuretics. Overall, 71% of rhPTH(1-84)−treated patients with baseline hypercalciuria had normal 24-h urinary calcium excretion at Month 36 (n=12/17). Treatment with rhPTH(1-84) improved calciumphosphate product from baseline 3.4 (0.5) mmol2/l2 (n=49) to 2.9 (0.5) mmol2/l2 (n=36) (P<0.0001). eGFR was baseline 108.2 (36.4) ml/min (n=41) and 115.7 (47.3) ml/min (n=36) at Month 36 (P<0.0772). Over 3 years, rhPTH(1-84) maintained target levels of serum calcium and reduced urinary calcium to normal levels in HPT patients. More information is needed to understand the timing of the beneficial effect on urinary calcium excretion.
20 - 23 May 2017
European Society of Endocrinology