Testosterone supplementation in healthy older men drives GH and IGF-I secretion without potentiating peptidyl secretagogue efficacy
Bibliographic record
Abstract
OBJECTIVE: Testosterone supplementation increases GH and IGF-I concentrations in healthy older men via unknown mechanisms. We examine the hypotheses that (i) testosterone amplifies stimulation of GH secretion by GH-releasing peptide (GHRP)-2 or GH-releasing hormone (GHRH) infused with l-arginine to limit somatostatin outflow (i.e. upregulates each agonistic pathway), (ii) testosterone augments the effect of both peptidyl secretagogues infused together (i.e. reduces opposition by hypothalamic somatostatin) and (iii) abdominal visceral fat (AVF) mass is a negative determinant of specific secretagogue-stimulated GH secretion. DESIGN: Randomized double-blind crossover design of placebo versus testosterone administration in healthy older men. METHODS: Deconvolution analysis was used to estimate basal GH secretion and the mass (integral) and waveform (time-shape) of GH secretory bursts. RESULTS: Statistical contrasts revealed that administration of testosterone compared with placebo in seven men aged 60-77 years increased fasting concentrations of GH (P < 0.01) and IGF-I (P = 0.003), and basal (P < 0.005) and pulsatile (P < 0.01) GH secretion. Testosterone did not alter the absolute value or rank order of secretagogue efficacy: l-arginine/GHRP-2 (23-fold effect over saline) = GHRH/GHRP-2 (20-fold) > l-arginine/GHRH (7.5-fold). Waveform reconstruction indicated that each stimulus pair accelerated initial GH secretion within a burst (P < 0.01). Regression analysis disclosed a significant inverse association between GH secretory-burst mass and computer tomography-estimated AVF following stimulation with l-arginine/GHRH after testosterone supplementation (R(2) = 0.54, P = 0.015). CONCLUSION: Supraphysiological testosterone concentrations augment GH and IGF-I production in the elderly male without altering maximal somatotrope responses to single and combined GHRH and GHRP-2 drive, thus predicting multifactorial mechanisms of testosterone upregulation.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".