What are the therapeutic effects, side effects, and monitoring recommendations of growth hormone (somatropin) therapy?

Growth Hormone Effects

Growth hormone (somatropin) therapy effectively promotes linear growth in children with growth hormone deficiency and improves body composition in both children and adults, with a generally favorable safety profile when properly monitored.

Therapeutic Effects

In Children

Growth hormone therapy produces substantial benefits in pediatric patients with growth hormone deficiency (GHD), chronic kidney disease (CKD), Turner syndrome, and idiopathic short stature 1:

• Height gains: Median increase of 1.1 SDS (standard deviation score) in standardized height, corresponding to approximately 7.4 cm in boys and 7.0 cm in girls when treated for at least 2 years 1
• Optimal dosing: 0.045–0.05 mg/kg/day by daily subcutaneous injection in the evening 1
• Growth velocity: Higher doses (28 IU/m² per week) produce 1.18 cm/year greater height velocity compared to lower doses (14 IU/m² per week) 1

In Adults

For adults with GHD, somatropin therapy provides metabolic and cardiovascular benefits 2, 3:

• Body composition: Increases lean body mass and reduces fat mass
• Bone health: Improves bone mineral density, particularly important during the transition period from pediatric to adult care when peak bone mass is still being achieved 2
• Cardiovascular effects: Improves endothelial function, reduces C-reactive protein and LDL cholesterol, decreases arterial stiffness, and may slightly lower blood pressure 2
• Quality of life: Enhances overall well-being and muscle strength 3

Side Effects and Safety Profile

Common and Manageable Side Effects

Registry data from large cohorts show NO significant association between GH therapy and malignancy, slipped capital femoral epiphysis, avascular necrosis, glucose intolerance, pancreatitis, rapid CKD progression, acute allograft rejection, or fluid retention 1.

However, specific adverse effects require monitoring:

Intracranial Hypertension

• Rare occurrence: 3 of 1,376 CKD patients in registry data 1
• Baseline fundoscopy required before initiation 1
• Immediate workup including fundoscopy needed if persistent headache or vomiting develops 1

Glucose Metabolism

• Insulin secretion increases during first year of treatment with persistent hyperinsulinemia 1
• GH treatment ≤5 years typically does NOT adversely affect glucose tolerance 1
• Close monitoring essential in obese patients due to increased risk of impaired glucose tolerance 1
• Insulin/hypoglycemic agent doses may require adjustment 4

Orthopedic Complications

• Slipped capital femoral epiphysis: Risk increased with rapid growth; obtain bone radiographs if symptoms occur and discontinue GH if confirmed 1, 5, 6
• Lipoatrophy: Rotate injection sites daily to prevent 1
• Scoliosis progression: Monitor in susceptible patients 5, 7

Endocrine Effects

• Secondary hyperparathyroidism: GH may aggravate this condition 1
• Withhold therapy if PTH >500 pg/ml; reinstitute when PTH returns to target range 1
• Ensure adequate treatment of CKD-mineral bone disease before initiating GH 1

Adrenal Function

• GH inhibits 11β-hydroxysteroid dehydrogenase type 1, potentially unmasking central hypoadrenalism 4
• Patients on glucocorticoid replacement may require increased maintenance or stress doses 4

Rare but Serious Effects

• Anaphylactic reactions and angioedema: Reported in post-marketing surveillance 4
• Benign intracranial hypertension: More common in children than adults 5, 6
• Leukemia: Reported in small numbers; unclear if related to GH therapy, underlying GHD pathology, or associated treatments like radiation 4

Monitoring Recommendations

Clinic visits every 3–6 months (more frequently for young patients and those with advanced CKD) to monitor 1:

• Growth parameters: Height, height velocity, pubertal development
• Skeletal maturation: Wrist radiography
• Laboratory tests:
  • Renal function
  • Thyroid hormones (TSH, free T3)
  • Serum glucose
  • Calcium, phosphate, bicarbonate
  • Parathyroid hormone levels
  • IGF-1 levels (to assess adherence and guide dosing)

Response Assessment

If height velocity in first year is <2 cm/year over baseline 1:

• Assess patient adherence to therapy
• Measure serum IGF-1 levels
• Verify weight-adjusted GH dosage
• Evaluate nutritional and metabolic factors

Drug Interactions

Critical Interactions

• Glucocorticoids: Pharmacologic doses attenuate growth-promoting effects; carefully adjust replacement therapy to avoid both hypoadrenalism and growth inhibition 4
• Oral estrogens: May reduce IGF-1 response, requiring higher somatropin doses in girls and women 4
• CYP450-metabolized drugs: Somatropin increases CYP450-mediated clearance; monitor drugs metabolized by liver enzymes (corticosteroids, sex steroids, anticonvulsants, cyclosporine) 4

Contraindications to Therapy

Do NOT start GH therapy in patients with 1:

• Closed epiphyses (absolute)
• Active malignancy (absolute)
• Acute critical illness (absolute)
• Severe secondary hyperparathyroidism (PTH >500 pg/ml)
• Proliferative or severe non-proliferative diabetic retinopathy
• First year after renal transplantation

Stop GH therapy immediately for 1:

• Epiphyseal closure
• Intracranial hypertension
• Slipped capital femoral epiphysis
• At time of renal transplantation
• Unexplained decrease in estimated glomerular filtration rate

Administration Details

• Bioavailability: ~80% after subcutaneous injection 1
• Pharmacokinetics: Tmax 3–6 hours, half-life 2–3 hours 1
• Timing: Evening injections to mimic physiological circadian rhythm 1
• Product selection: Both reference and biosimilar products recommended for use 1

Common Pitfalls to Avoid

1. Starting with excessive doses: Begin with recommended 0.045–0.05 mg/kg/day and adjust based on IGF-1 levels and clinical response to minimize fluid-related adverse effects 3
2. Inadequate monitoring of glucose metabolism: Particularly critical in obese patients and those with nephropathic cystinosis 1
3. Failing to address secondary hyperparathyroidism before initiation: This can lead to unmasking of renal osteodystrophy 1
4. Discontinuing therapy during transition period: Stopping GH for >18 months when linear growth has ceased but bone mass is still accruing can be detrimental 2
5. Not adjusting glucocorticoid doses: Concomitant glucocorticoid therapy requires careful adjustment to avoid inhibiting growth effects 4