IGF-1
The hormone that carries out most of growth hormone's growth effects, given as mecasermin to children whose bodies cannot make it
IGF-1 is the growth factor the liver releases in response to growth hormone, and it carries out much of that hormone's effect on growth. Recombinant IGF-1, mecasermin, is approved as Increlex for children with severe primary IGF-1 deficiency. In the blood of adults, both high and low levels track disease risk.
What is it?
Growth hormone acts largely through IGF-1: it drives the protein-building and bone-lengthening effects that make children grow. Laron syndrome shows what happens without it. People with this primary IGF-1 deficiency and growth hormone resistance grow slowly from birth, and untreated adults reach 100 to 138 cm. Growth hormone cannot help them, because their bodies do not respond to it.
Recombinant IGF-1, mecasermin, can. In 76 children with severe deficiency treated for up to 12 years, height velocity rose from 2.8 to 8.0 cm a year in the first year, then stayed above baseline for up to eight years. National series tell the same story: in Poland height SD score rose by about 1.5 over three years, and a global registry of 102 patients reaching near-adult height found a gain of 0.9 SD, more if treatment started before puberty, though only one in ten with Laron syndrome reached the normal range.
Hypoglycaemia is the main risk, affecting 49% in the long-term study and about a quarter of registry patients, most often young children and those with Laron syndrome; that is why the label says to inject it within 20 minutes of a meal or snack. Increlex is approved for growth failure in children aged two and older with severe primary IGF-1 deficiency, or with growth hormone gene deletion and neutralising antibodies to it. The label starts at 0.04 to 0.08 mg/kg twice daily and allows up to 0.12; it is not a substitute for growth hormone.
Rare growth disorders downstream of growth hormone respond too: siblings with STAT5B deficiency grew faster on it, and children with PAPP-A2 deficiency gained height and bone density. Beyond growth, results are mixed. In Duchenne muscular dystrophy it doubled growth but did nothing for walking. In the extreme insulin resistance of Donohue and Rabson-Mendenhall syndromes it helped early glucose control but did not prevent later diabetes. It is under study for Rett syndrome.
In adults, IGF-1 is mostly a measurement. In 440,185 UK Biobank participants, high levels protected younger people but tracked more disease in older ones, and both extremes carried risk.
Mechanism of Action
Mecasermin is recombinant human IGF-1, the hormone that carries out most of growth hormone's growth effects.
IGF-1 receptor
Activates the IGF-1 receptor in growth plates, muscle and other tissues.
Bypasses GH resistance
Works where growth hormone cannot, as in Laron syndrome or GH gene deletion with antibodies.
Insulin-like effect
Lowers glucose, so it is injected within 20 minutes of a meal (label).
Published Research
These are the studies that describe IGF-1, read from their PubMed abstracts: a 12-year treatment study, a population cohort and two reviews.
Twelve years of treatment
76 children with IGF-1 deficiency from growth hormone insensitivity took 60 to 120 µg/kg twice daily. Height velocity rose from 2.8 to 8.0 cm a year in year one; hypoglycaemia affected 49% and injection-site lipohypertrophy 32%.
Too much and too little
In 440,185 UK Biobank participants, high serum IGF-1 protected younger people but tracked more disease and death in older ones, risk was U-shaped overall, and cancer risk rose more uniformly with it.
Adult height on mecasermin
In 102 registry patients treated with recombinant IGF-1 for a median 3.9 years, height SD score rose 0.9 on average; only 10.5% with Laron syndrome reached normal adult height.
Hypoglycaemia on mecasermin
In 306 registry patients, 80 had at least one hypoglycaemia event; younger age, Laron syndrome and earlier hypoglycaemia predicted it.
Three years in Poland
In Polish children with severe primary IGF-1 deficiency, mecasermin raised height SD score by 1.45 over three years, with the biggest gain in the first year; adverse events were mild and temporary in most.
Duchenne muscular dystrophy
In boys with Duchenne muscular dystrophy, 6 months of recombinant IGF-1 doubled growth velocity (6.5 against 3.3 cm a year) and increased lean mass but did not change 6-minute walk distance.
Three siblings with STAT5B deficiency
In three siblings with STAT5B deficiency, growth velocity rose from 3.0-5.2 to 4.8-7.4 cm a year over the first three years, then fell when adherence dropped during the pandemic.
PAPP-A2 deficiency: bone
In two children with PAPP-A2 deficiency, two years of treatment increased height, bone mineral density and trabecular bone score without adverse events.
Extreme insulin resistance syndromes
In children with Donohue and Rabson-Mendenhall syndromes, recombinant IGF-1 improved early glycaemic control and fasting tolerance, but two infants died and the two longest-lived patients still progressed to diabetes.
Heart checks in Laron syndrome
Children with Laron syndrome on mecasermin had normal cardiac examinations, electrocardiograms and echocardiograms, except one child with unexplained pulmonary hypertension.
PAPP-A2 deficiency into adulthood
Two Spanish siblings with PAPP-A2 deficiency treated twice daily for six years both reached their target height, with bone density normalising and no hypoglycaemia; one had growth of the kidneys and spleen.
What Laron syndrome shows
Untreated, people with primary IGF-1 deficiency reach 100 to 136 cm (women) or 109 to 138 cm (men); biosynthetic IGF-1 raised growth to 8 to 9 cm in the first year of treatment.
IGF-1 and the arteries
A review of clinical and animal evidence that IGF-1, from the circulation and from artery walls, has protective effects on atherosclerosis.
Dosing Data
Increlex is injected under the skin twice daily within 20 minutes of a meal or snack, starting at 0.04 to 0.08 mg/kg and titrated up to 0.12 mg/kg.
Educational information, not medical advice. Each dose above is tagged with its source: an approved label, a published human study, animal data, or amounts reported by users. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose. Full medical disclaimer.
Side Effects & Contraindications
Reported Side Effects
From the Increlex label and the treatment study above.
Contraindications & Cautions
Set by the label.
Legal Status
Recombinant IGF-1 is FDA-approved for severe primary IGF-1 deficiency.
Frequently Asked Questions
?What is IGF-1?
A growth factor released mainly in response to growth hormone that carries out much of that hormone's effect on growth.
?Who gets it as a drug?
Children with severe primary IGF-1 deficiency, or growth hormone gene deletion with antibodies to it, as Increlex.
?Does it work?
In 76 children, growth rose from 2.8 to 8.0 cm a year in the first year of treatment.
?Is a higher level better?
Not for older adults: in a 440,185-person cohort, high levels tracked more disease with age.
?Why must it be taken with food?
IGF-1 lowers blood glucose like insulin. Hypoglycaemia affected 49% of children in the long-term study, so the label says to inject it within 20 minutes of a meal or snack.
?Does it help conditions other than Laron syndrome?
Small studies report faster growth in STAT5B and PAPP-A2 deficiency, but in Duchenne muscular dystrophy it improved growth without improving walking, and in extreme insulin resistance it did not prevent later diabetes.
References
- [fda-pi] INCRELEX (mecasermin) injection Prescribing Information, sections 1, 2 and 12.3 (DailyMed version 5, effective May 18, 2026; read September 30, 2026).
- [pubmed] Chernausek SD, et al. "Long-term treatment with recombinant insulin-like growth factor (IGF)-I in children with severe IGF-I deficiency due to growth hormone insensitivity." J Clin Endocrinol Metab, 2007;92(3):902-10. PMID: 17192294.
- [pubmed] Zhang WB, et al. "The antagonistic pleiotropy of insulin-like growth factor 1." Aging Cell, 2021;20(9):e13443. PMID: 34363732.
- [pubmed] Laron Z. "Insulin-like growth factor 1 (IGF-1): a growth hormone." Mol Pathol, 2001;54(5):311-6. PMID: 11577173.
- [pubmed] Higashi Y, et al. "IGF-1 and cardiovascular disease." Growth Horm IGF Res, 2019;45:6-16. PMID: 30735831.
- [other] US FDA, Drugs@FDA (openFDA): INCRELEX (mecasermin), BLA 021839, prescription. Read September 30, 2026.
- [pubmed] Ramon-Krauel M, et al. "Near-Adult Height Outcomes in Patients Treated With rhIGF-1 for Severe Growth Failure: Real-World IGFD Registry Data." J Clin Endocrinol Metab, 2026;111(2):e500-e511. PMID: 40626687.
- [pubmed] Bang P, et al. "Frequency and Predictive Factors of Hypoglycemia in Patients Treated With rhIGF-1: Data From the Eu-IGFD Registry." J Clin Endocrinol Metab, 2023;109(1):46-56. PMID: 37579214.
- [pubmed] Petriczko E, et al. "Treatment of severe primary IGF-1 deficiency using rhIGF-1 preparation - first three years of Polish experience." Endokrynol Pol, 2019;70(1):20-27. PMID: 30351442.
- [pubmed] Rutter MM, et al. "Recombinant human insulin-like growth factor-1 therapy for 6 months improves growth but not motor function in boys with Duchenne muscular dystrophy." Muscle Nerve, 2020;61(5):623-631. PMID: 32108355.
- [pubmed] Muthuvel G, et al. "Recombinant Human Insulin-Like Growth Factor-1 Treatment of Severe Growth Failure in Three Siblings with STAT5B Deficiency." Horm Res Paediatr, 2024;97(2):195-202. PMID: 37586336.
- [pubmed] Hawkins-Carranza FG, et al. "rhIGF-1 Treatment Increases Bone Mineral Density and Trabecular Bone Structure in Children with PAPP-A2 Deficiency." Horm Res Paediatr, 2018;89(3):200-204. PMID: 29455208.
- [pubmed] Improda N, et al. "Clinical spectrum of extreme insulin resistance syndromes treated with rhIGF-1: A single-center experience." J Clin Endocrinol Metab, 2026;111(7):2049-2063. PMID: 41606799.
- [pubmed] Erol N, et al. "Cardiac examination in children with Laron syndrome undergoing mecasermin therapy." J Pediatr Endocrinol Metab, 2018;31(6):675-679. PMID: 29750649.
- [pubmed] Martín-Rivada Á, et al. "Adult height and long-term outcomes after rhIGF-1 therapy in two patients with PAPP-A2 deficiency." Growth Horm IGF Res, 2021;60-61:101419. PMID: 34358737.
Sources & Citations
Studies were read from their PubMed abstracts; the Increlex label (DailyMed version 5, effective May 18, 2026) was read September 30, 2026.
Medical Disclaimer: This content is for educational and informational purposes only. It is not medical advice, and nothing here is an instruction to obtain or use any compound. Talk to a licensed clinician about your own situation.