title: Analysis of the impact of intravenous LH pulses versus continuous LH infusion on testosterone secretion during GnRH-receptor blockade.
abstract: Gonadotrophin-releasing hormone (GnRH) pulsatility is required for optimal luteinizing hormone (LH) secretion, but whether LH pulsatility is required for physiological testosterone (T) secretion is not known. To test the postulate that pulses of recombinant human (rh) LH stimulate greater T secretion than continuous infusion of the same dose, a potent selective GnRH antagonist was administered overnight to 19 healthy men ages 18-49 yr. Subjects then received saline or rhLH intravenously continuously or as 6-min pulses intravenously every 1 or 2 h at the same total dose. Blood was sampled every 10 min for 10 h to quantify T responses. For the four interventions, the descending rank order of mean LH and mean T concentrations was 1-h = 2-h rhLH pulses > continuous rhLH > saline (P < 10(-3)). Plateau LH and T concentrations correlated positively (R(2) = 0.943, P = 0.029) as did LH concentrations and LH half-lives (R(2) = 0.962, P = 0.019). Percentage pulsatile T secretion assessed by deconvolution analysis (Keenan DM, Takahashi PY, Liu PY, Roebuck PD, Nehra AX, Iranmanesh A, Veldhuis JD. Endocrinology 147: 2817-2828, 2006) was the highest (P = 0.019), and half-time to attain peak T concentrations was the shortest (P < 10(-6)), for 1-h rhLH pulses. Approximate entropy (a pattern-regularity measure) revealed more orderly T secretion for 1- than 2-h rhLH pulses (P = 0.0076). Accordingly, a pulsatile LH signal, while not obligatory to maintain mean T concentrations, controls the mean plasma LH concentration and determines quantifiable patterns of T secretion. These data introduce the question whether blood T patterns in turn supervise distinctive target-tissue responses.
authors.affiliation: Endocrine Research Unit, Dept. of Internal Medicine, Mayo School of Graduate Medical Education, Center for Translational Science Activities, Mayo Clinic, Rochester, MN 55905, USA. veldhuis.johannes@mayo.edu
authors.forename: Johannes D
authors.initials: JD
authors.lastname: Veldhuis
authors.forename: Peter Y
authors.initials: PY
authors.lastname: Liu
authors.forename: Paul Y
authors.initials: PY
authors.lastname: Takahashi
authors.forename: Suanne M
authors.initials: SM
authors.lastname: Weist
authors.forename: Jean R
authors.initials: JR
authors.lastname: Wigham
mesh_terms: D000293:Adolescent; D000328:Adult; D000818:Animals; D018592:Cross-Over Studies; D004334:Drug Administration Schedule; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D007986:Luteinizing Hormone / Q000008:administration & dosage* / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D011966:Receptors, LHRH / Q000037:antagonists & inhibitors*; D013739:Testosterone / Q000378:metabolism*; D055815:Young Adult
chemical_list: D011966:Receptors, LHRH; D007987:Gonadotropin-Releasing Hormone; D013739:Testosterone; D007986:Luteinizing Hormone; C061018:ganirelix