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Most children with deficient pituitary function secrete inadequate
amounts of growth hormone (GH); therefore, the term hypopituitarism is
used interchangeably with growth hormone deficiency (GHD).
Children who have diabetes insipidus caused by isolated deficiency
of antidiuretic hormone (discussed in Chapter 525)
and those uncommon children who have isolated gonadotropin deficiency
(Kallmann syndrome; see Chapter 541) are exceptions.
They have normal GH secretion but pituitary dysfunction of posterior
and anterior pituitary lobes, respectively. GHD is the most common
endocrinologic cause of the insulin-like growth factordeficiency (IGFD)
syndrome.
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Deficiency of GH can occur alone (isolated GHD) or in conjunction
with overt deficiency of one or more other pituitary hormones (the
term panhypopituitarism refers to multiple pituitary
hormone deficiencies). Although there are exceptions, patients with
multiple pituitary hormonal deficiencies tend to have more severe
GHD.
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The best estimate of incidence of GHD in the US population is
often cited as being about 1:3480. However, acquired, idiopathic,
isolated GHD may be overdiagnosed. Growth hormone (GH)-treated patients
with GHD (as defined by a stimulated GH level of < 10 ng/mL)
account for about 60% of all treated patients of whom 78% have “idiopathic” GHD and
22% have “acquired” or “organic” (neoplasms,
trauma, inflammation, miscellaneous) causes of GHD.
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Around 300 patients with inherited abnormalities of the GH receptor
have been identified. Potentially, a larger group of individuals
with heterozygous abnormalities of the GH receptor will be added
to this group with abnormalities such as defects of GH receptor
signaling (JAK-STAT) and defects of the insulin-like growth factor
I (IGF-I) gene.
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Differential Diagnosis
of Growth Hormone Deficiency (Hypopituitarism)
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The causes of hypopituitarism include disorders of the pituitary
gland and hypothalamic disorders that impair the release of growth
hormone-releasing hormone (GHRH), as listed in Table
523-1.
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Hypothalamic
Dysfunction
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Idiopathic hypopituitarism with growth failure
due to growth hormone deficiency (GHD) may appear at the end of
the first year after birth. This disorder has been postulated to
be due to brith complications because as many as 70% of children
with idiopathic hypopituitarism have histories of some form of perinatal
insult, such as ...