title: The lack of effect of insulin on luteinizing hormone pulsatility in healthy male volunteers provides evidence of a sexual dimorphism in the metabolic regulation of reproductive hormones.
abstract: BACKGROUND
  The activity of the neuroendocrine reproductive axis is closely related to nutritional status. This link is particularly important in healthy women, in whom insulin is a positive signal for the reproductive system. In contrast, very little is known regarding this relation in men.
  
  
  OBJECTIVE
  This study was designed to evaluate the effect of insulin on the reproductive axis of young male volunteers and to study the effect of short-term hypercaloric feeding on this modulation.
  
  
  METHODS
  The activity of the neuroendocrine reproductive axis was characterized by the pattern of endogenous luteinizing hormone (LH) secretion on the basis of frequent blood sampling protocols. The effect of insulin was tested by comparing the LH secretion pattern between a baseline study and a hyperinsulinemic euglycemic clamp. These studies were performed first in subjects fed a controlled isocaloric diet for 6 d (calculated as 1.5 times their resting metabolic rate) then in the same subjects fed a controlled hypercaloric diet in which 30% extra calories were provided as fat and fructose (3 g · kg(-1) · d(-1)) before undergoing identical protocols. Serum gonadotropins, sex steroids, glucose, insulin, ghrelin, and leptin concentrations were assessed, and the HOMA-IR was calculated.
  
  
  RESULTS
  The LH secretion pattern was not affected by insulin or by hypercaloric feeding. Insulin decreased ghrelin and increased leptin concentrations but had no additional effect of hypercaloric feeding despite significantly lower HOMA-IR indexes.
  
  
  CONCLUSIONS
  Our data indicate that neither insulin nor short-term hypercaloric feeding has any effect on the activity of the male reproductive axis. They also further support the association between ghrelin and insulin and glucose metabolism. This trial was registered at clinicaltrials.gov as NCT01058681.
authors: Service of Endocrinology, Diabetology and Metabolism, Department of Medicine, Lausanne University Hospital, Switzerland.
authors: Marie-Hélène
authors: MH
authors: Pesant
authors: Andrew
authors: A
authors: Dwyer
authors: Pedro
authors: P
authors: Marques Vidal
authors: Philippe
authors: P
authors: Schneiter
authors: Vittorio
authors: V
authors: Giusti
authors: Luc
authors: L
authors: Tappy
authors: François P
authors: FP
authors: Pralong
mesh_terms: D000293:Adolescent; D000328:Adult; D001786:Blood Glucose / Q000032:analysis; D018592:Cross-Over Studies; D002149:Energy Intake; D005640:Follicle Stimulating Hormone / Q000097:blood / Q000378:metabolism; D054439:Ghrelin / Q000097:blood; D006062:Gonadotropins / Q000097:blood; D006801:Humans; D007328:Insulin / Q000097:blood*; D020738:Leptin / Q000097:blood; D007986:Luteinizing Hormone / Q000097:blood* / Q000378:metabolism*; D008297:Male; D009752:Nutritional Status; D011446:Prospective Studies; D012098:Reproduction / Q000187:drug effects*; D012727:Sex Characteristics; D013972:Thyrotropin / Q000097:blood / Q000378:metabolism; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D054439:Ghrelin; D006062:Gonadotropins; D007328:Insulin; D020738:Leptin; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D013972:Thyrotropin