Take the decline at the fast end of the range the endocrinologists give, half every seven years [3]. Four decades past a pubertal peak works out to about 5.7 halvings, which leaves roughly 2 percent of peak; at the slow end, one halving per decade, four halvings leave about 6 percent [18]. Restoring youthful levels in a 60-year-old therefore means an increase of 16-fold to more than 50-fold [19] in a hormone that in adults also acts on blood sugar, bone density and muscle [4]. "As much as half" is a ceiling rather than a central estimate, so read those figures as the outer edge of the physiology, not the typical case. The word doing quiet work in the sales copy is "natural" [6], since the natural level of a 60-year-old pituitary is the low one.
Anne Cappola, an endocrinologist at the University of Pennsylvania, puts the reasoning error plainly: anything that decreases with age gets nominated as the cause of aging [10]. Whether adults should be raising growth hormone at all is a question Scientific American leaves open [21], and none of the compounds on sale answers it.
The strongest number in the category was measured in people almost nobody buying peptides resembles. Tesamorelin's approval covers HIV-associated lipodystrophy [13], and in a trial of more than 400 patients with that condition visceral fat fell by about 15 percent on the drug [14]. Visceral fat is the deposit tied to chronic disease and premature death [20], so that is a real effect on an endpoint worth having, though it says nothing about what happens to muscle, since Alexander Pastuszak of the University of Utah says the drug was aimed at reducing fat tissue rather than building muscle [15], and it says nothing about anyone without the disease either.
Sermorelin's gap has a different shape. Its 1997 approval was for children with growth hormone deficiency, and it left the market in 2008 for commercial reasons [11], so what that history establishes is pharmacodynamic: the injection raises growth hormone. Performance, body composition and longevity in healthy adults have not been through large randomized controlled trials, Pastuszak says [12]. For CJC-1295, ipamorelin, GHRP-2 and GHRP-6 there is no approval at all, and the same asymmetry holds, with hormone levels up and effects on muscle and fat unproven [16].
Stacking is why this will not be settled from the demand side. With several peptides in the same protocol [17], no user can allocate their own result to a single vial, which is why testimonial volume never accumulates into evidence. My read, with the condition attached: this category has a demonstrated effect on a biomarker and no demonstrated effect on the outcomes being advertised, and it would take a randomized trial in healthy adults with body composition and function as endpoints to move me off that. The experts quoted also call the risks serious [9], and that gap runs in both directions: the harms in this population remain about as unmeasured as the benefits.
