THU154 The Effects Of Combined Arginine And Sinemet Stimulation On Copeptin Levels In The Pediatric Population

Disclosure: S. Sastry: None. C. March: None. L. Garibaldi: None. M.J. McPhaul: None. S. Wheeler: None. Introduction: Most agents that stimulate the secretion of growth hormone (GH) also induce secretion of copeptin (COP), a stable surrogate of AVP. For the evaluation of the polyuria-polydipsia syndrome (PPS), COP stimulation by intravenous (IV) arginine (ARG) has been proposed as a less invasive test than those based on osmotic stimulation of the posterior pituitary, though it provides a weaker stimulus in children than in adults (∼30% vs. 50% increase). After having observed a robust COP response to combined ARG and insulin stimulation (March C, Horm Res Pediatr 2023, PMID: 36513057), we explored the effect of combined IV ARG and oral L-Dopa/carbidopa (LDc, 10:1 ratio), another known stimulus for GH secretion, on COP secretion in non-AVP deficient children. Subjects and Methods: We enrolled 30 healthy subjects with short stature (73% male, mean age ± SD 10.5±3.0 years) undergoing fasting GH stimulation testing in a prospective, single-arm study to assess their COP response. At 0 minutes (min), ARG (500 mg/kg) was infused over 30 min IV and LDc (200 mg/m2 BSA of L-Dopa) was given orally. Serum COP (B.R.A.H.M.S Kryptor assay, Quest Diagnostics) was measured at 0, 60, 90 and 120 min. Results: Median (interquartile range (IQR)) COP values (pmol/L) were 8 (5-10) at 0 min, 17 (13-44) at 60 min, 24 (13-41) at 90 min, and 30 (16-56) at 120 min. Peak COP concentrations at 60, 90, and 120 min all increased significantly from baseline (p