Head to head
IGF-1 LR3 against Somatropin
Growth hormone works largely by raising IGF-1, so people ask why not take the IGF-1 directly. One of these is an approved medicine with defined indications and the other is an unapproved analogue whose published record is animal work.
Column A
IGF-1 LR3Long R3 Insulin-like Growth Factor 1
A long-acting analogue of IGF-1 studied in animal models for muscle growth and tissue repair.
Column B
SomatropinSomatropin (recombinant human growth hormone)
FDA-approved recombinant human growth hormone used for growth hormone deficiency and several other approved indications.
Side by side, on the facts we can check
| Attribute | IGF-1 LR3 | Somatropin |
|---|---|---|
| Category | Growth Hormone | Growth Hormone |
| FDA status | Not FDA-approved | FDA-approved for GH deficiency and other indications |
| Half-life | ~20-30 hours | ~3-4 hours (subcutaneous) |
| Molecular weight | 9,111 Da | 22,124 Da |
| Mechanism | Activates the IGF-1 receptor, driving cellular growth, proliferation, and protein synthesis; reduced binding-protein affinity prolongs activity. | Directly activates growth hormone receptors, raising IGF-1 and driving growth, protein synthesis, and metabolic effects. |
| Human studies cited | 0 | 2 |
| Legal status, US | Not approved; research use only | FDA-approved, prescription only |
Frequently asked questions
What is the difference between IGF-1 LR3 and Somatropin?
IGF-1 LR3: A long-acting analogue of IGF-1 studied in animal models for muscle growth and tissue repair. Somatropin: FDA-approved recombinant human growth hormone used for growth hormone deficiency and several other approved indications.
Which has stronger research evidence, IGF-1 LR3 or Somatropin?
This database does not grade compounds. It counts what was run in people: 0 of the 3 studies cited on the IGF-1 LR3 profile were human work, against 2 of 3 for Somatropin. Those counts are of our own citation lists and understate any larger literature, and neither is a recommendation.
Are IGF-1 LR3 and Somatropin FDA-approved?
IGF-1 LR3: Not FDA-approved. Somatropin: FDA-approved for GH deficiency and other indications.
Reviewed Sep 2026. This page sets two published records side by side. It is educational, it is not medical advice, and it contains no dosing protocols or recommendations for personal use.