Short-term testosterone supplementation does not activate GH and IGF-I production in postmenopausal women.
BACKGROUND
Testosterone (Te), oestradiol, GH and IGF-I concentrations fall in postmenopausal women.


OBJECTIVE
To test the effect of increased Te availability on impoverished GH/IGF-I secretion in this context.


METHODS
Placebo (Pl) and a low vs. high dose of Te were administered transdermally for 7 days to each of 15 healthy older women (ages 48-81 years) in a randomized, double-blind crossover design.


METHODS
Frequent blood sampling, GHRP-2 (Growth hormone releasing peptide-2) infusion, and deconvolution analysis were used to assess GH secretion.


RESULTS
Graded Te supplementation increased serum Te concentrations (nmol/l) from 0.87 +/- 0.06 [Pl] to 5 +/- 1 [low] and 7.3 +/- 1.6 [high] (P < 0.001), but did not affect: (i) pulsatile GH secretion (microg/l/12 h; conversion factor: 1 microg/l = 0.33 mU/l), 29 +/- 7.2, 32 +/- 5.6 and 27 +/- 4.9; (ii) GH regularity (approximate entropy), 0.52 +/- 0.05, 0.57 +/- 0.05 and 0.56 +/- 0.05; (iii) IGF-I concentrations (microg/l; conversion factor: 1 microg/l = 0.131 nmol/l), 126 +/- 13, 135 +/- 15 and 141 +/- 13; (iv) IGFBP-3 (mg/l), 3.7 +/- 0.2, 3.6 +/- 0.1 and 3.7 +/- 0.2; (v) IGFBP-1 (microg/l), 41 +/- 2.3, 44 +/- 3.8 and 44 +/- 3.2; and (vi) the mass of GH secreted (microg/l/3 h) after GHRP-2 injection, 123 +/- 27, 146 +/- 32 and 147 +/- 38.


CONCLUSIONS
Up to 8-fold elevation of Te concentrations for 1 week in postmenopausal women does not detectably amplify GH secretion or action, thus indicating that low androgen availability is not a proximate acute mediator of hyposomatotropism in postmenopausal individuals.
Soares-Welch
Cacia
C
Endocrine Research Unit, Department of Internal Medicine, Mayo School of Graduate Medical Education, General Clinical Research Center, Mayo Clinic, Rochester, MN 55905, USA.
Mielke
Kristi L
KL
Bowers
Cyril Y
CY
Veldhuis
Johannes D
JD
D000368:Aged; D000369:Aged, 80 and over; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D004958:Estradiol / Q000008:administration & dosage / Q000097:blood; D005260:Female; D013007:Growth Hormone-Releasing Hormone / Q000502:physiology; D019382:Human Growth Hormone / Q000096:biosynthesis*; D006801:Humans; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000097:blood; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis*; D008875:Middle Aged; D009842:Oligopeptides / Q000008:administration & dosage / Q000097:blood; D017698:Postmenopause / Q000502:physiology*; D013739:Testosterone / Q000008:administration & dosage* / Q000097:blood
D018970:Insulin-Like Growth Factor Binding Protein 1; D018972:Insulin-Like Growth Factor Binding Protein 3; D009842:Oligopeptides; D019382:Human Growth Hormone; D013739:Testosterone; D004958:Estradiol; D007334:Insulin-Like Growth Factor I; D013007:Growth Hormone-Releasing Hormone; C091874:growth hormone-releasing peptide-2