growth%20hormone%20deficiency
GROWTH HORMONE DEFICIENCY
Growth hormone deficiency in adults reflects an absence of two hormones, growth hormone and insulin-like growth factor-1 (IGF-1), affecting the process of glucose-insulin metabolism, lipolysis and bone remodelling.
History may show pituitary adenoma, surgery &/or radiation treatment of pituitary adenomas or cranial radiation for other disorders, deficiency of other pituitary hormones that may occur concurrently with growth hormone deficiency, and previous childhood growth hormone deficiency.
Physical exam reveals reduced lean body mass with increased weight, body fat predominantly in the abdominal region, thin & dry skin, cool peripheries, poor venous access and blunt affect.

Pharmacotherapy

Somatropin

  • A synthetic polypeptide human growth hormone of recombinant deoxyribonucleic acid (DNA) origin

Factors affecting dosing:

  • Physiologic factors
    • Pubertal girls & premenopausal women secrete more growth hormone (GH) than their male counterpart mainly due to the underlying estrogen-antagonistic effects on GH action in women
      • Higher GH doses are therefore required among female patients
  • Concomitant medications
    • Use of oral estrogen as replacement therapy or for contraception purposes in women renders them more GH-resistant than men, thus, requiring a higher dose to achieve equivalent insulin-like growth factor-1 (IGF-1) responses
    • Use of transdermal estrogen patches may help lower the GH dose needed to achieve equivalent IGF-1I response
  • Obesity
    • Characterized by marked decrease in both spontaneous & stimulated GH secretion but w/ normal or low-normal serum IGF-1 levels which is probably secondary to enhanced hepatic responsiveness to exogenous GH
      • Obese GH-deficient patients may be started on low doses (0.1-0.2 mg/day) to reduce risk of worsening glucose tolerance
  • Compliance
    • Patients may at times find difficulty complying w/ daily injections
    • Using the same total weekly dose, patients may administer his/her injections on an alternate day or thrice-weekly basis
  • Other factors that may increase GH dose: Low serum IGF-1 levels, young patients regardless of type
  • Others factors that may decrease GH dose: High serum IGF-1 levels, elderly patients, worsening glucose tolerance, side effects

Growth Hormone (GH) Replacement Therapy

Adults

  • Indicated for growth hormone deficiency (GHD) due to pituitary diseases from known causes (eg pituitary tumor, irradiation, trauma, reconfirmed childhood GHD, etc)
  • Aim for serum IGF-1 levels in the middle of the normal range appropriate for age & sex, except when side effects are significant
    • Consider a trial of higher GH doses as long as serum IGF-1 levels remain w/in the normal range
  • Effects:
    • Increase in bone density
    • Increase in lean tissue
    • Decrease in adipose tissue
    • Modulate lipoprotein metabolism [eg decreased serum low-density lipoprotein (LDL)]
    • Improved mood & motivation
    • Improved exercise capacity
    • Increase in cardiac contractility
  • Use lower GH doses (0.1-0.2 mg/day) in all patients w/ diabetes or who are susceptible to glucose intolerance
  • It is recommended to retest patients transitioning from pediatric to adult care (especially those w/ isolated GHD)

Children

  • Indicated for GHD in children
  • Effects:
    • Induce normal statural growth
    • Correction of hypoglycemia
  • Target for treatment:
    • Satisfactory response is defined as an increase of height velocity of at least 2 cm/year above pretreatment velocity
    • Achieve acceptable adult height
  • Replacement is continued until attainment of bone age of 14 years (girls) & 16 years (boys) or if the child has achieved at least 10th percentile of adult height
  • In certain patients, surgical therapy may also be needed for congenital anomalies & pituitary tumors
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