Chapter 523

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.

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.

### Epidemiology

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.

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.

### Differential Diagnosis of Growth Hormone Deficiency (Hypopituitarism)

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.

Table 523-1. Causes of Growth Hormone Deficiency Leading to Insulin-Like Growth Factor Type I Deficiency Syndrome

#### Hypothalamic Dysfunction

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 ...

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