Rising IGF-1 levels helped explain some of the muscle growth from the drug, but not all of it—so other factors are also at work.
Scientific Claim
In HIV-positive adults with abdominal obesity who responded to tesamorelin with ≥8% VAT reduction, the effect of tesamorelin on muscle area was attenuated by IGF-1 changes, indicating that IGF-1 contributes to, but does not fully explain, muscle growth.
Original Statement
“In contrast, changes in total and lean muscle area were independent of VAT but not IGF-1 changes. Although our findings suggest that the tesamorelin effect on muscle area may be more related to the IGF-1 effects rather than the VAT reduction, our results are limited by the inclusion of VAT responders only.”
Evidence Quality Assessment
Claim Status
appropriately stated
Study Design Support
Design supports claim
Appropriate Language Strength
probability
Can suggest probability/likelihood
Assessment Explanation
The study uses regression adjustments to infer mediation, but IGF-1 was not experimentally manipulated. 'Contributes to' appropriately reflects probabilistic inference.
Evidence from Studies
Supporting (0)
Contradicting (1)
The Growth Hormone Releasing Hormone Analogue, Tesamorelin, Decreases Muscle Fat and Increases Muscle Area in Adults with HIV
The study shows that the drug makes muscles bigger and stronger in people with HIV and belly fat, but it never looked at or mentioned IGF-1, so we can’t tell if IGF-1 is involved or not.