Long-acting growth hormones explained
Three once-weekly products, three different ways of making GH last a week.
Checked 2026-10-22 Researched and written by Kymata Health Editorial · Sources cited inline Report an error
Short answer
Three once-weekly growth hormones have US labels: somapacitan (Sogroya) binds albumin, somatrogon (Ngenla) carries extra hCG peptides, and lonapegsomatropin (Skytrofa) is a prodrug that releases ordinary somatropin. All act on the GH receptor like daily somatropin. Their labels differ in who they cover and when IGF-1 is measured.
How does each one last a week?
Somapacitan is GH with one amino-acid change and an albumin-binding group; binding to albumin slows its clearance, for a half-life of about 2 to 3 days in adults (Sogroya label).
Somatrogon is GH fused to three copies of a short peptide from hCG, giving a larger molecule with an effective half-life of 37.7 hours in children (Ngenla label).
Lonapegsomatropin is somatropin bound to a polyethylene-glycol carrier by a linker that breaks at a steady rate, releasing unchanged somatropin through the week (Skytrofa label).
Who is each one approved for in the US?
Sogroya: adults with GH deficiency, and children 2.5 and older with GH deficiency, short stature after being born small for gestational age, Noonan syndrome or idiopathic short stature (Sogroya label). Ngenla: children 3 and older with GH deficiency only (Ngenla label). Skytrofa: children 1 and older (at least 11.5 kg) with GH deficiency, and adults with GH deficiency since July 2025 (Skytrofa label).
When is IGF-1 measured on a weekly GH?
Because levels rise and fall across the week, the labels time the blood draw: 3 to 4 days after the previous dose for Sogroya (Sogroya label) and 4 to 5 days for Skytrofa (Skytrofa label). On Ngenla, IGF-1 peaks about 2 days after a dose and reaches its weekly average about 4 days after (Ngenla label).
Are the warnings different from daily GH?
The headings are the same as daily somatropin's: acute critical illness, active cancer, Prader-Willi syndrome, glucose intolerance, intracranial hypertension, fluid retention, adrenal and thyroid effects, and in children hip and spine problems (Genotropin label; Sogroya label; Ngenla label; Skytrofa label).
Frequently asked questions
Questions
- Is a weekly GH stronger than daily somatropin?
- They act on the same GH receptor as daily somatropin; what changes is how often it is injected and how levels rise and fall across the week.
- Can the weekly products be used for anti-aging?
- None is labelled for it. US law (21 U.S.C. 333(e)) bars distributing GH for any use other than treating a disease or recognized condition on a physician's order.
Not medical advice This page summarises published labels and studies. It is not a recommendation to use any product; a clinician decides.