Growth Hormone Deficiency

Pediatricsmedium

A 9-year-old boy is much shorter than his classmates. Both parents are of average height. Height is 120 cm, below the 3rd percentile, and weight is 25 kg. He is chubby with mid-facial hypoplasia and normal body proportions. Thyroid stimulating hormone is 3.2 U/L, insulin-like growth factor 1 is 18 ng/mL (normal 67 to 405), and bone age is 6 years. Which of the following is the most likely diagnosis?

  1. A.Familial short stature
  2. B.Growth hormone deficiencyCorrect
  3. C.Constitutional delay of growth and puberty
  4. D.Acquired primary hypothyroidism

Explanation

The combination of severe short stature, a markedly delayed bone age, a low insulin-like growth factor 1, normal thyroid function, and relative overweight for height points to growth hormone deficiency. Growth hormone acts largely through hepatic insulin-like growth factor 1, so a low level in a child with normal nutrition and normal thyroid function is the best single screening test; a random growth hormone level is useless because secretion is pulsatile and is usually undetectable between pulses. Children with growth hormone deficiency characteristically have increased subcutaneous truncal fat, immature facies with mid-facial hypoplasia, and a delayed bone age that is well behind chronological age. In familial short stature the child is short but the bone age matches chronological age, growth velocity is normal, and the parents are short, none of which fit here. Constitutional delay also produces a delayed bone age, but growth velocity and insulin-like growth factor 1 are normal or only mildly low and there is usually a family history of late puberty; the profoundly low insulin-like growth factor 1 here argues against it. Hypothyroidism must always be excluded before labelling a child growth hormone deficient because it produces an identical growth pattern, but the thyroid stimulating hormone is normal. Confirmation requires two growth hormone provocation tests, followed by magnetic resonance imaging of the pituitary and hypothalamus to look for a structural lesion such as craniopharyngioma or ectopic posterior pituitary. Treatment is daily recombinant growth hormone until epiphyseal fusion or growth velocity falls below 2 to 2.5 cm per year.

Why each option

A.
In familial short stature the bone age equals the chronological age, growth velocity is normal, and the parents are short.
B.
Correct. Low insulin-like growth factor 1 with markedly delayed bone age, normal thyroid function, and increased adiposity for height is the classic profile.
C.
Constitutional delay shows a delayed bone age but a normal insulin-like growth factor 1 and normal growth velocity, with a family history of late puberty.
D.
Hypothyroidism gives a similar picture but is excluded by the normal thyroid stimulating hormone.

Reference: Nelson Textbook of Pediatrics, 22nd ed., 2024

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