OBJECTIVE: Growth hormone (GH) secretion declines with age and is affected by body composition. The signal that mediates the latter relationship remains III-defined. Leptin, the protein product of the adipocyte specific ob gene, is thought to accurately reflect fat mass and could therefore be a candidate to influence GH secretion. We have therefore investigated the relationship between GH status, leptin and body composition in normal and GH-deficient elderly subjects. DESIGN: GH Secretion was assessed by 20-minute sampling over 24 hours and serum leptin concentrations were measured in a single morning, fasted sample. PATIENTS: Twenty-one GH deficient elderly patients (61-83 years) and 22 gender- and BMI-matched controls (61-88 years). MEASUREMENTS: Body composition was assessed by dual-energy X-ray absorptiometry (DEXA). GH was measured in an ultrasensitive chemiluminescent assay and serum leptin was determined by radio-immunoassay. RESULTS: Leptin was correlated with percentage body fat in both sexes (male r = 0.75, female r = 0.89, both P < 0.001). Male patients had increased fat mass (FM) (P < 0.01) and leptin concentrations (P < 0.05) but similar lean mass (LM) compared with controls. However, leptin concentration per unit FM was identical in both groups (P = 0.3). In contrast, female patients had lower LM (P < 0.05) but similar FM to controls, yet their leptin concentration per unit FM was twice that of the controls (P < 0.05). In multiple linear regression (MLR) leptin was determined positively by FM and negatively by LM (controls r2 = 76%; patients r2 = 73%, both P < 0.0001). When controlled for gender, GH secretion in the controls was correlated negatively with leptin (r = -0.68, P < 0.01) and negatively with percentage body fat (r = -0.73, P < 0.01). In MLR, using leptin as a marker of body composition, 66% of the variability in GH secretion in the controls could be explained by gender (38%) and by leptin (28%). CONCLUSIONS: Both decreased lean mass and increased fat mass raise serum leptin concentrations in normal and growth hormone-deficient elderly subjects. Leptin is therefore a marker of body composition rather than fat mass alone. The influence of body composition on growth hormone secretion in the elderly may be mediated through leptin, acting as a peripheral signal from adipose tissue to decrease GH secretion.
OBJECTIVE:Growth hormone (GH) secretion declines with age and is affected by body composition. The signal that mediates the latter relationship remains III-defined. Leptin, the protein product of the adipocyte specific ob gene, is thought to accurately reflect fat mass and could therefore be a candidate to influence GH secretion. We have therefore investigated the relationship between GH status, leptin and body composition in normal and GH-deficient elderly subjects. DESIGN:GH Secretion was assessed by 20-minute sampling over 24 hours and serum leptin concentrations were measured in a single morning, fasted sample. PATIENTS: Twenty-one GH deficient elderly patients (61-83 years) and 22 gender- and BMI-matched controls (61-88 years). MEASUREMENTS: Body composition was assessed by dual-energy X-ray absorptiometry (DEXA). GH was measured in an ultrasensitive chemiluminescent assay and serum leptin was determined by radio-immunoassay. RESULTS:Leptin was correlated with percentage body fat in both sexes (male r = 0.75, female r = 0.89, both P < 0.001). Male patients had increased fat mass (FM) (P < 0.01) and leptin concentrations (P < 0.05) but similar lean mass (LM) compared with controls. However, leptin concentration per unit FM was identical in both groups (P = 0.3). In contrast, female patients had lower LM (P < 0.05) but similar FM to controls, yet their leptin concentration per unit FM was twice that of the controls (P < 0.05). In multiple linear regression (MLR) leptin was determined positively by FM and negatively by LM (controls r2 = 76%; patients r2 = 73%, both P < 0.0001). When controlled for gender, GH secretion in the controls was correlated negatively with leptin (r = -0.68, P < 0.01) and negatively with percentage body fat (r = -0.73, P < 0.01). In MLR, using leptin as a marker of body composition, 66% of the variability in GH secretion in the controls could be explained by gender (38%) and by leptin (28%). CONCLUSIONS: Both decreased lean mass and increased fat mass raise serum leptin concentrations in normal and growth hormone-deficient elderly subjects. Leptin is therefore a marker of body composition rather than fat mass alone. The influence of body composition on growth hormone secretion in the elderly may be mediated through leptin, acting as a peripheral signal from adipose tissue to decrease GH secretion.
Authors: Ramona Ramachandran; Kristofer S Gravenstein; E Jeffrey Metter; Josephine M Egan; Luigi Ferrucci; Chee W Chia Journal: J Am Geriatr Soc Date: 2012-03-14 Impact factor: 5.562
Authors: G Radetti; C Tinelli; C Paganini; M Draghi; D Scarcella; E Bozzola; G Aimaretti; G Rondini; L Tatò Journal: J Endocrinol Invest Date: 2002-10 Impact factor: 4.256
Authors: C Chen; S G Roh; G Y Nie; K Loneragan; R W Xu; M Ruan; L J Clarke; J W Goding; A Gertler Journal: Endocrine Date: 2001-02 Impact factor: 3.925
Authors: Huseyin Begenik; Mehmet Aslan; Ahmet Cumhur Dulger; Habib Emre; Ahu Kemik; Ozgur Kemik; Ramazan Esen Journal: Arch Med Sci Date: 2015-04-23 Impact factor: 3.318