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. Design/patients 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. Measurements: 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 (μg/l/12 h; conversion factor: 1 μg/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 (μg/l; conversion factor: 1 μg/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 (μg/l), 41 ± 2.3, 44 ± 3.8 and 44 ± 3.2; and (vi) the mass of GH secreted (μg/l/3 h) after GHRP-2 injection, 123 ± 27, 146 ± 32 and 147 ± 38. Conclusion: 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.