What is the proper usage and dosage of Somatropin (recombinant human growth hormone) for treating growth hormone deficiency?

Somatropin for Growth Hormone Deficiency

For children with growth hormone deficiency, somatropin should be administered at 0.045-0.05 mg/kg/day via daily subcutaneous injections at night, initiated when height is below the 3rd percentile and height velocity is below the 25th percentile, after addressing other treatable causes of growth failure. 1, 2, 3

Patient Selection Criteria

Pediatric Patients

Initiate therapy when ALL of the following are met:

• Height below the 3rd percentile for age and sex 1, 4
• Height velocity below the 25th percentile 1, 4
• Growth potential remains (open epiphyses confirmed by bone age radiograph) 2, 4, 3
• Other treatable causes have been adequately addressed 1, 4

Pre-treatment requirements include:

• Screen and treat hypothyroidism (TSH, free T4) first, as this is a reversible cause that must be corrected before GH therapy 4
• Evaluate for celiac disease (tissue transglutaminase IgA, total IgA) and chronic anemia 4
• Obtain wrist radiograph for bone age assessment 2, 4
• In CKD patients, ensure metabolic acidosis, malnutrition, and mineral bone disorder are optimized 1, 4

Adult Patients

Two dosing approaches are available: 3

• Weight-based: Start at ≤0.006 mg/kg daily, titrate to maximum 0.025 mg/kg daily (age ≤35 years) or 0.0125 mg/kg daily (age >35 years) 3
• Non-weight-based: Start at 0.2 mg/day (range 0.15-0.3 mg/day), increase by 0.1-0.2 mg/day every 1-2 months based on response 3

Dosing Protocols by Indication

Standard Pediatric GHD

• 0.3 mg/kg/week divided into daily subcutaneous injections 3
• In pubertal patients, up to 0.7 mg/kg/week divided daily may be used 3

CKD-Related Growth Failure

• 0.35 mg/kg/week divided into daily subcutaneous injections 1, 3
• Continue until final height or renal transplantation 1, 3
• Timing for dialysis patients: 3
  • Hemodialysis: Inject at night before sleep or ≥3-4 hours post-dialysis to prevent hematoma
  • CCPD: Inject in morning after completing dialysis
  • CAPD: Inject in evening at time of overnight exchange

Post-Transplant Patients

• Initiate 1 year after transplantation if spontaneous catch-up growth does not occur and steroid-free immunosuppression is not feasible 1, 4
• Use same dosing as pre-transplant CKD patients 1

Turner Syndrome

• 0.375 mg/kg/week divided into 3-7 doses per week 3

Idiopathic Short Stature

• 0.3 mg/kg/week divided into daily injections 3

Administration Technique

Critical administration details:

• Administer at night via subcutaneous injection to mimic physiological circadian rhythm 2, 3
• Rotate injection sites daily (thigh, upper arm, abdomen, or buttock) to prevent lipoatrophy 2, 3
• Use sterile, disposable needles 3
• Allow refrigerated solution to reach room temperature and gently swirl before use 3
• Do NOT inject if solution is cloudy or contains particles after warming 3

Monitoring Protocol

Clinical consultations every 3-6 months to assess: 2, 4

• Height and growth velocity 2, 4
• Pubertal development 2, 4
• Skeletal maturation via wrist radiography 2, 4
• Thyroid function (TSH, free T3) 2
• Metabolic parameters: glucose, calcium, phosphate, bicarbonate 2

If growth velocity in first year is <2 cm/year above baseline, evaluate: 2, 4

• Patient adherence to daily injections 2, 5
• Serum IGF-1 levels 2, 4
• Dose adjustment based on current weight 2, 4
• Nutritional and metabolic optimization 2

Absolute Contraindications

Do NOT initiate therapy in: 2, 4, 3

• Closed epiphyses 2, 4, 3
• Active malignancy 2, 4, 3
• Critical acute illness 2, 4, 3
• Severe secondary hyperparathyroidism (PTH >500 pg/mL) 2, 4
• Known hypersensitivity to somatropin or excipients 2, 3

Serious Adverse Events Requiring Immediate Evaluation

Monitor for and immediately evaluate: 2, 4

• Intracranial hypertension: Perform baseline fundoscopy before starting; evaluate immediately for persistent headache or vomiting 2
• Slipped capital femoral epiphysis: Obtain radiographs if hip/knee pain or limping develops 2
• Glucose intolerance: Monitor glucose metabolism, especially in obese patients 2, 4
• Worsening secondary hyperparathyroidism 2
• Fluid retention 2

Treatment Discontinuation Criteria

Discontinue therapy when: 2

• Epiphyseal closure occurs 2, 3
• Persistent severe secondary hyperparathyroidism (PTH >500 pg/mL) develops 2
• Intracranial hypertension occurs 2
• Slipped capital femoral epiphysis develops 2
• Inadequate response despite optimal nutritional/metabolic control 2
• Unexplained decrease in estimated glomerular filtration rate 2

Consider discontinuation when: 2

• Patient reaches target genetic height percentile 2
• Accelerated bone maturation occurs 2

Common Pitfalls to Avoid

Poor adherence is the most common cause of treatment failure - children with high adherence to daily injections grow significantly more than those with low adherence 5. The daily injection burden can lead to suboptimal effectiveness throughout childhood 6.

Starting treatment too late significantly compromises final height outcomes - final height correlates with pretreatment age, height SDS, and duration of therapy 7. Early recognition and treatment initiation are essential for optimal outcomes 7.

Inadequate glucocorticoid replacement in ACTH-deficient patients can impair growth response - the major cause of mortality in children with both GH and ACTH deficiency is adrenal crisis and hypoglycemia 7. Ensure appropriate glucocorticoid dosing without excess 7.

In adult patients, older individuals and obese patients require lower starting doses - they are more prone to adverse effects, particularly fluid retention 3, 8. Estrogen-replete women may require higher doses than men, and oral estrogen increases dose requirements 3.