Somatropin !
Recombinant human growth hormone, injected under the skin. It treats growth failure in children and growth hormone deficiency in adults.
Updated 2026-11-01
Also called: Recombinant human growth hormone (rhGH)
The figure shows human growth hormone (the same protein as somatropin) bound to the extracellular domains of its receptor.
Mechanism of action
Somatropin has the same amino acid sequence as pituitary growth hormone. It binds its receptor dimer, activating JAK2 and STAT5. The liver releases IGF-1, which stimulates chondrocytes at the growth plates, so long bones lengthen while the plates are open. Growth hormone also promotes protein synthesis and fat breakdown and opposes insulin, raising blood glucose.
- Somatropin binds the growth hormone receptor dimer
- JAK2 and STAT5 are activated inside the cell
- The liver releases IGF-1
- IGF-1 drives growth at the open growth plates
Pharmacokinetics
- Absorption
- Injected subcutaneously, usually daily; not active by mouth
- Metabolism
- Broken down like other proteins, in the liver and kidney
Indications
- Growth failure from growth hormone deficiency in children
- Other causes of short stature approved for treatment (for example Turner or Prader-Willi syndrome)
- Adult growth hormone deficiency, for example after pituitary disease Pituitary adenoma →
- HIV-associated wasting and short bowel syndrome (selected products)
Adverse effects
Common
- Injection-site pain, redness, swelling or skin thickening
- Headache
- Muscle and joint pain
- Swelling of hands and feet, tingling (fluid retention)
Contraindications
- Use for growth after the growth plates have closed
- Active cancer
- Acute critical illness after heart or abdominal surgery, trauma or serious breathing failure
- Active diabetic retinopathy
Key interactions
- Insulin and oral antidiabetic drugs
- Growth hormone lowers insulin sensitivity and raises glucose; control is checked
What is monitored
- Height and growth velocity in children
- IGF-1
- Blood glucose
- Thyroid function
- Spine (scoliosis) and hips
Administration and safety
- Injected under the skin with a pen or syringe; sites are rotated
- Pens and cartridges are stored and mixed as each product describes; they are not shared
- Different products are not interchangeable without an order
Nursing care
- Measure height and weight at each visit and plot them on a growth chart
- Ask about headache with vision changes, limp or hip or knee pain, and abdominal pain
- Check glucose, especially with diabetes or obesity
- Teach injection technique, site rotation and storage
Pregnancy and breastfeeding
Data in pregnancy are limited; the treating doctor is told if pregnancy occurs during treatment.
Test yourself
Think of the answer, then tap the question to see it.
Why does somatropin stop increasing height after puberty?
Bone lengthening needs open growth plates; once the epiphyses close, IGF-1 can no longer lengthen long bones.
A child on somatropin has headache, vomiting and blurred vision. What complication is suspected?
Intracranial hypertension; a fundus exam looks for papilloedema.
Which laboratory marker is used to follow somatropin treatment?
IGF-1, together with growth velocity in children.
Related drugs
Related conditions
← Back to the class: Growth hormone
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Somatropin Injection: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2025); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026); Farmacología básica y clínica (Katzung), 16.ª ed., cap. 37 (McGraw Hill, 2025).
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Representative model, for educational purposes only.