Growth Hormone (GH) Deficiency

Key Features

• Characterized by decreased growth velocity and delayed skeletal maturation in the absence of other explanations

• May be isolated or coexist with other pituitary hormone deficiencies

• May be congenital (septo-optic dysplasia or ectopic posterior pituitary), genetic (GH or GHRH gene mutation), or acquired (craniopharyngioma, germinoma, histiocytosis, or cranial irradiation)

• Idiopathic GH deficiency is the most common deficiency state with an incidence of about 1:4000 children

Clinical Findings

• Features of infantile GHD include

  • Normal birth weight and slightly reduced length

  • Hypoglycemia (if accompanied by adrenal insufficiency)

  • Micropenis (if accompanied by gonadotropin deficiency)

  • Conjugated hyperbilirubinemia (if other pituitary hormone deficiencies present)

• Growth retardation in isolated GH deficiency and hypopituitarism may not present until late in infancy or childhood

• Excess truncal adiposity seen in many patients because GH promotes lipolysis

Diagnosis

• Laboratory tests to assess GH status may be difficult to interpret because there is significant overlap in GH secretion between normal and GH-deficient children

• GH secretion is pulsatile, so random samples for measurement of serum GH are of no value in the diagnosis of GH deficiency

• Serum concentrations of IGF-1 give reasonable estimations of GH secretion and action in the adequately nourished child and are often used as a first step in the evaluation for GH deficiency

• IGF-binding protein 3 (IGFBP-3) is a much less sensitive marker of GH deficiency, but may be useful in the underweight child or in children younger than 4 years, since it is less affected by age or nutritional status

• All patients diagnosed with GHD should have an MRI of the hypothalamus and pituitary gland.

Treatment

• Indications for GH therapy

  • GH deficiency

  • Gowth restriction associated with chronic kidney failure

  • Turner, Prader-Willi, and Noonan syndromes

  • Children born small for gestational age (SGA) who do not demonstrate catch-up growth by age 4

  • SHOX gene mutations

• GH therapy has also been approved for children with idiopathic short stature whose current height is more than 2.25 standard deviations below the normal range for age

• With GH treatment, final height may be 5–7 cm taller in this population

• Recommended treatment schedule is subcutaneous recombinant GH given subcutaneously 7 days per week with total weekly dose of 0.15–0.3 mg/kg

• Side effects of recombinant GH are uncommon but include benign intracranial hypertension and slipped capital femoral epiphysis