title: Discordance of IGF-1 and GH stimulation testing for altered GH secretion in obesity.
abstract: OBJECTIVE
  To investigate the concordance/discordance of IGF-1 and peak stimulated GH in identifying subjects with reduced GH secretion and to determine the physiological significance of any discordance in obese subjects.
  
  
  METHODS
  95 obese and 43 normal weight men and women underwent measurement of IGF-1 and GH stimulation testing with GH releasing hormone (GHRH)-arginine. Reduced IGF-1 and GH secretion were defined using pre-determined cut-points. Cardiovascular disease risk was determined by measuring carotid intima-media thickness (cIMT). In a second study, IGF-1 was measured in 52 obese men and women who underwent GH stimulation testing and overnight frequent blood sampling. The association of IGF-1 and peak stimulated GH with parameters of endogenous GH secretion was assessed.
  
  
  RESULTS
  60% of obese subjects had normal IGF-1 and peak stimulated GH while 8.4% of obese subjects had reduced IGF-1 and GH secretion. Discordance rate for IGF-1 and peak GH was 31.6%. Subjects with both low IGF-1 and low peak GH had the highest cIMT, while subjects with both normal IGF-1 and peak GH had the lowest cIMT. Subjects with reduction in either IGF-1 or peak GH, had intermediate cIMT (P=0.02). IGF-1 and peak stimulated GH were associated with maximum and mean overnight serum GH and GH AUC as well as maximum peak mass and median pulse mass. Peak stimulated GH, but not IGF-1, was also associated with nadir overnight serum GH concentration and basal GH secretion.
  
  
  CONCLUSIONS
  Peak stimulated GH and IGF-1 demonstrate significant discordance in identification of subjects with reduced GH secretion in obesity. Subjects with reduction of either IGF-1 or peak GH had higher cIMT compared to subjects with both normal IGF-1 and peak GH. Subjects with reductions in both IGF-1 and peak GH had the highest cIMT. Peak GH, compared to IGF-1, has broader associations with various parameters of endogenous GH secretion which support its utility in identifying those with reduced GH secretion.
authors.affiliation: Program in Nutritional Metabolism and Neuroendocrine Unit, Massachusetts General Hospital, Boston, MA 02114, United States; Harvard Medical School, Boston, MA 02114, United States; Pediatric Endocrine Unit, Massachusetts General Hospital, Boston, MA 02114, United States.
authors.forename: Takara L
authors.initials: TL
authors.lastname: Stanley
authors.affiliation: Program in Nutritional Metabolism and Neuroendocrine Unit, Massachusetts General Hospital, Boston, MA 02114, United States; Harvard Medical School, Boston, MA 02114, United States.
authors.forename: Meghan N
authors.initials: MN
authors.lastname: Feldpausch
authors.affiliation: Program in Nutritional Metabolism and Neuroendocrine Unit, Massachusetts General Hospital, Boston, MA 02114, United States; Harvard Medical School, Boston, MA 02114, United States.
authors.forename: Caitlin A
authors.initials: CA
authors.lastname: Murphy
authors.affiliation: Program in Nutritional Metabolism and Neuroendocrine Unit, Massachusetts General Hospital, Boston, MA 02114, United States; Harvard Medical School, Boston, MA 02114, United States.
authors.forename: Steven K
authors.initials: SK
authors.lastname: Grinspoon
authors.affiliation: Program in Nutritional Metabolism and Neuroendocrine Unit, Massachusetts General Hospital, Boston, MA 02114, United States; Harvard Medical School, Boston, MA 02114, United States. Electronic address: hmakimura@partners.org.
authors.forename: Hideo
authors.initials: H
authors.lastname: Makimura
mesh_terms: D000293:Adolescent; D000328:Adult; D015992:Body Mass Index; D002339:Carotid Arteries / Q000473:pathology*; D016022:Case-Control Studies; D005260:Female; D019382:Human Growth Hormone / Q000378:metabolism* / Q000494:pharmacology*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood / Q000145:classification*; D017539:Tunica Intima / Q000473:pathology; D017540:Tunica Media / Q000473:pathology; D055815:Young Adult
chemical_list: D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I
keywords: AutoDecon; Carotid intima-media thickness; Deconvolution analyses; Frequent sampling; GH; GH stimulation test; GHRH–arginine; IGF-1