“Selective” is a comparative pharmacology term, not a synonym for harmless. The original ipamorelin paper needs to be read within the experiments that established its selectivity claim. Primary report
Study observations
The development program tested ipamorelin in rat pituitary cells, rats, and conscious swine. It elicited growth-hormone release, while the swine hormonal profiling showed a different ACTH and cortisol response pattern from certain comparator secretagogues. Receptor-antagonist experiments supported a GHRP-like pathway. The report presented these findings as a basis for further clinical development. Primary report
Our appraisal: selectivity depends on the tested panel
A selectivity statement needs a target, comparison, biological system, exposure range, and measurement time. Without those details, the word can imply that every possible off-target effect was excluded, which no finite assay panel can establish.
The animal-to-human boundary is particularly important here. Endocrine responses in swine and cells are informative pharmacology, but they do not by themselves establish human outcomes, long-term tolerability, or effects in people with endocrine disease.
The comparator also matters. Being more selective than another tested secretagogue is not the same as being free from all adverse consequences. It is a relative observation under the study's conditions.
Before release, inspect the complete hormone panel, group sizes, assay methods, and exposure comparisons. Do not convert the paper's interest in future clinical development into a claim that development was already successful. Separate human clinical studies must be evaluated on their own endpoints.
Frequently asked questions
Was this principally a human outcomes trial?
No. It reported preclinical pharmacology.
Did it include rat pituitary cells?
Yes, along with animal experiments.
Where was hormonal selectivity specifically profiled?
The abstract describes that assessment in swine.
Does selectivity mean no possible harms?
No. It is bounded by the measurements and comparisons.
Can these findings establish muscle or recovery benefits in humans?
No. Those outcomes require direct evidence.
Does a comparator advantage establish absolute safety?
No. Relative and absolute claims are different.
What is the review scope?
The primary indexed abstract, with complete experimental review pending.