TY - JOUR
T1 - Continuation of growth hormone (GH) substitution during fasting in GH-deficient patients decreases urea excretion and conserves protein synthesis
AU - Nørrelund, Helene
AU - Møller, Niels
AU - Nair, K. Sreekumaran
AU - Christiansen, Jens Sandahl
AU - Jørgensen, Jens Otto Lunde
PY - 2001
Y1 - 2001
N2 - The consequences of GH deficiency during conditions in which endogenous GH release is acutely stimulated are largely unknown. Short-term fasting constitutes a robust GH stimulus, but the metabolic significance of GH during fasting is uncertain. To address both of these issues, we therefore evaluated the effect of GH on substrate metabolism during fasting in adults with GH deficiency. Seven hypopituitary GH-deficient patients were each studied twice during a 40-h fast: once with GH replacement continued and once with GH discontinued during the fast. After 40 h of fasting, protein synthesis and turnover were higher with than without GH replacement [phenylalanine incorporation (μmol/kg fat free mass/h): 36.6 ± 1.2 (GH) vs. 32.8 ± 1.4, P < 0.05; phenylalanine flux (μmol/kg fat free mass/h): 41.3 ± 1.0 (GH) vs. 38.0 ± 1.8, P < 0.05]. During continued GH replacement, urea excretion decreased during night-time [urea excretion (mmol/24 h): 269 ± 51 (GH) vs. 390 ± 69, P 0.05], and a significant decline in urea-N synthesis rate was found [urea-N synthesis rate (mmol/h): 14.7 ± 1.6 (GH) vs. 21.1 ± 2.2, P 0.01]. GH replacement was associated with increased lipid oxidation [lipid oxidation (mg/kg per min): 0.91 ± 0.07 (GH) vs. 0,70 ± 0.03, P 0.05]. Finally, continuation of GH induced moderate elevations in plasma glucose levels without significant changes in total glucose turnover or oxidation. In summary, continued GH substitution during fasting conserves nitrogen, which involves stimulation or maintenance of protein synthesis. Our data support the importance of GH replacement in hypopituitary adults.
AB - The consequences of GH deficiency during conditions in which endogenous GH release is acutely stimulated are largely unknown. Short-term fasting constitutes a robust GH stimulus, but the metabolic significance of GH during fasting is uncertain. To address both of these issues, we therefore evaluated the effect of GH on substrate metabolism during fasting in adults with GH deficiency. Seven hypopituitary GH-deficient patients were each studied twice during a 40-h fast: once with GH replacement continued and once with GH discontinued during the fast. After 40 h of fasting, protein synthesis and turnover were higher with than without GH replacement [phenylalanine incorporation (μmol/kg fat free mass/h): 36.6 ± 1.2 (GH) vs. 32.8 ± 1.4, P < 0.05; phenylalanine flux (μmol/kg fat free mass/h): 41.3 ± 1.0 (GH) vs. 38.0 ± 1.8, P < 0.05]. During continued GH replacement, urea excretion decreased during night-time [urea excretion (mmol/24 h): 269 ± 51 (GH) vs. 390 ± 69, P 0.05], and a significant decline in urea-N synthesis rate was found [urea-N synthesis rate (mmol/h): 14.7 ± 1.6 (GH) vs. 21.1 ± 2.2, P 0.01]. GH replacement was associated with increased lipid oxidation [lipid oxidation (mg/kg per min): 0.91 ± 0.07 (GH) vs. 0,70 ± 0.03, P 0.05]. Finally, continuation of GH induced moderate elevations in plasma glucose levels without significant changes in total glucose turnover or oxidation. In summary, continued GH substitution during fasting conserves nitrogen, which involves stimulation or maintenance of protein synthesis. Our data support the importance of GH replacement in hypopituitary adults.
UR - http://www.scopus.com/inward/record.url?scp=17844367322&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=17844367322&partnerID=8YFLogxK
U2 - 10.1210/jc.86.7.3120
DO - 10.1210/jc.86.7.3120
M3 - Article
C2 - 11443176
AN - SCOPUS:17844367322
SN - 0021-972X
VL - 86
SP - 3120
EP - 3129
JO - Journal of Clinical Endocrinology and Metabolism
JF - Journal of Clinical Endocrinology and Metabolism
IS - 7
ER -