PubMed
Ciliary neurotrophic factor (CNTF) and related peptides in neuroprotection
Peterson WM, Wang Q, Tzekova R, et al. Prog Retin Eye Res. 2013
Compare
P21 vs Retatrutide
Side-by-side observational reports from PeptIQ users. This compares self-reported patterns — not clinical head-to-head trials.
Last reviewed . By the PeptIQ team.
Observational reporting only — not medical advice. Does not recommend doses, protocols, or treatments.
P21
6 community reports
Overall experience
From check-in ratings — separate from side effects logged below. Side effects are logged separately from overall experience. A favorable check-in can still include nausea, fatigue, or injection-site reactions.
Favorable 100% · Mixed 0% · Unfavorable overall 0%
Most reported benefits
Benefits users selected when logging a favorable or mixed check-in.
Cognition
6
Mood
6
Sleep
3
Self-reported dose per injection
Median bucket: 200–400 mcg · Most common: 200–400 mcg
Reports span 100–400 mcg
100–200
2
200–400
4
Anonymized self-reports from PeptIQ users — not prescribing guidance. Buckets group similar logged amounts; open-ended top buckets mean “at least” that dose.
Commonly stacked with
Retatrutide
125 community reports
Overall experience
From check-in ratings — separate from side effects logged below. Side effects are logged separately from overall experience. A favorable check-in can still include nausea, fatigue, or injection-site reactions.
Favorable 99% · Mixed 1% · Unfavorable overall 0%
Most reported benefits
Benefits users selected when logging a favorable or mixed check-in.
Appetite
222
Most logged side effects
Side effects are logged separately from overall experience. A favorable check-in can still include nausea, fatigue, or injection-site reactions.
Nausea
3
Self-reported dose per injection
Median bucket: 2–3 mg · Most common: 1–2 mg
Reports span 0 to ≥ 5 mg (open-ended top bucket)
0–0.01 mg
5
0.1–0.2 mg
3
0.2–0.4 mg
6
0.4–0.6 mg
10
0.6–1 mg
5
1–2 mg
80
2–3 mg
35
3–5 mg
17
5+ mg
61
Anonymized self-reports from PeptIQ users — not prescribing guidance. Buckets group similar logged amounts; open-ended top buckets mean “at least” that dose.
Commonly stacked with
How repeat users are trending
Among repeat reporters, 100% said they felt similar to their last entry, 0% more positive, and 0% more negative.
Overall, repeat reporters leaned similar or mixed compared to their previous entry.
Median gap between entries: 51 days · Based on 45 repeat reporters
Sources (8)
Published sources linked on the P21 and Retatrutide wiki pages.
- Wiki study page →Source
- Wiki study page →Source
PubMed
The effect of exogenous ciliary neurotrophic factor on cell cycle and neural differentiation markers of in vitro model cells: New insights for future therapeutic approaches
Ghasemi M, Alizadeh E, Motlagh BF, et al. Cell biochemistry and function. 2021
- Wiki study page →Source
PubMed
Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes
Rosenstock J, Frias J, Jastreboff AM, et al. Lancet. 2023
- Wiki study page →Source
PubMed
Triple-Hormone-Receptor Agonist Retatrutide for Obesity - A Phase 2 Trial
Jastreboff AM, Kaplan LM, Frias JP, et al. N Engl J Med. 2023
- Wiki study page →Source
ClinicalTrials.gov
Retatrutide obesity studies on ClinicalTrials.gov
ClinicalTrials.gov. Clinical trial registry. 2024
- Wiki study page →Source
ClinicalTrials.gov
Retatrutide studies on ClinicalTrials.gov
ClinicalTrials.gov. Clinical trial registry. 2024
- Wiki study page →Source
PubMed
Triple-Hormone-Receptor Agonist Retatrutide for Obesity - A Phase 2 Trial
Jastreboff AM, Kaplan LM, Frías JP, et al. The New England journal of medicine. 2023
- Wiki study page →Source
PubMed
Retatrutide-A Game Changer in Obesity Pharmacotherapy
Katsi V, Koutsopoulos G, Fragoulis C, et al. Biomolecules. 2025