Pharmacokinetics of growth hormone secretion in humans induced by growth hormone releasing hormone.
This investigation compares the age- and sex-related changes in growth hormone (GH) response to growth hormone releasing hormone (GHRH) in normal subjects using an appropriate pharmacokinetic model. Twenty-five subjects (14 males and 11 females) aged 23-89 yr received a single intravenous bolus dose (1 microgram/kg) of GHRH-40 solution. Plasma GH concentration-time profiles are best characterized by a biexponential equation (or one-compartment model) with first-order release and disappearance rates and an equilibration lag time. The harmonic mean release rate half-life is similar for both sexes (males: 12.6 min vs. females; 11.4 min) but significantly different across age groups (23-35 yr: 7.2 min vs. 50-89 yr: 16.8 min). The mean disappearance rate half-life and GHRH-equilibration time lag for females (33.6 and 20.4 min, respectively) and the higher age group subjects (32.4 and 21.6 min, respectively) are significantly longer than those of males (22.8 and 9 min, respectively) and the lower age-group subjects (21.6 and 8.4 min, respectively). The mean metabolic clearance rate of GH is significantly lower (p less than 0.02) for females than for males (3.1 vs. 4.83 ml/hr.m2). However, the production rate and the amount of GH released by the pituitary for our subjects appear to be very similar for both males (8.7 micrograms/hr.m2 and 4.65 micrograms/m2) and females (9.33 micrograms/hr.m2 and 5.11 micrograms/m2).
Gupta
S K
SK
Department of Psychiatry, Duke University Medical Center, Durham, NC 27710.
Krishnan
R R
RR
Ellinwood
E H
EH
Ritchie
J C
JC
Nemeroff
C B
CB
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology; D005260:Female; D013006:Growth Hormone / Q000096:biosynthesis / Q000097:blood / Q000378:metabolism*; D013007:Growth Hormone-Releasing Hormone / Q000493:pharmacokinetics* / Q000494:pharmacology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010902:Pituitary Gland / Q000378:metabolism; D012727:Sex Characteristics
D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone