Porth's Essentials of Pathophysiology, 4e

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lesion is clinically suspected. After the cause of short stature has been determined, treatment can be initiated. Idiopathic Short Stature. Idiopathic short stature, also referred to as normal-variant short stature, is short stature of undefined cause. 11–13 It has been defined as a condition in which the height of an individual is more than 2 standard deviations below the corresponding mean height for a given age, sex, and population group without evidence of systemic, endocrine, nutritional, or chromosomal abnormalities. 10 This definition includes children with familial short stature and constitutional delay in growth and puberty. Children with familial short stature tend to be well proportioned and to have a height close to the midparental height of their parents. The midparental height for boys can be calculated by adding 13 cm (5 inches) to the height of the mother, adding the father’s height, and dividing the total by two. For girls, 13 cm (5 inches) is subtracted from the father’s height, the result is added to the mother’s height, and the total is divided by two. 9 Ninety-five percent of normal children are within 8 cm (i.e., ±2 standard deviations) of the midparental height. Constitutional delay in growth and puberty describes children (particularly boys) who have moderately short stature, thin build, delayed skeletal and sexual matura- tion, and absence of other causes of decreased growth. Catch-up growth is a term used to describe an abnor- mally high growth rate that occurs as a child approaches normal height for age. It also occurs after the initiation of therapy for GH deficiency and hypothyroidism and the correction of chronic diseases. 9 Psychosocial Dwarfism. Psychosocial dwarfisminvolves a functional hypopituitarism and is seen in some emotion- ally deprived children. These children usually present with poor growth, potbelly, and poor eating and drinking hab- its. Typically, there is a history of disturbed family rela- tionships in which the child has been severely neglected or disciplined. Often, the neglect is confined to one child in the family. Growth hormone function usually returns to normal after the child is removed from the constraining environment. The prognosis depends on improvement in behavior and catch-up growth. Family therapy usually is indicated, and foster care may be necessary. Growth Hormone and Insulin-Like Growth Factor Deficiencies in Children. There are several forms of GH deficiency that present in childhood. Children with idiopathic GH deficiency lack the hypothalamic GHRH but have adequate somatotropes, whereas children with pituitary tumors or agenesis of the pituitary lack somatotropes. Congenital GH deficiency is associated with a shorter than normal birth length, followed by a decrease in growth rate that can be identified by careful measure- ment during the first year and that becomes obvious by 1 to 2 years of age. Children with classic GH deficiency have normal intelligence, short stature, obesity with immature facial features, and some delay in skeletal maturation (Fig. 32-2). Puberty often is delayed, and

males with the disorder have microphallus (abnormally small penis), especially if the condition is accompanied by gonadotropin-releasing hormone (GnRH) deficiency. In the neonate, GH deficiency can lead to hypoglyce- mia and seizures; if ACTH deficiency also is present, the hypoglycemia often is more severe. Acquired GH deficiency develops in later childhood. It may be caused by a hypothalamic-pituitary tumor, particularly if it is accompanied by other pituitary hormone deficiencies. When short stature is caused by a GH deficiency, GH replacement therapy is the treatment of choice. Growth hormone is species specific, and only human GH is effec- tive in humans. Human GH is now produced by recom- binant deoxyribonucleic acid (DNA) technology, and is available in adequate supply. The hormone is adminis- tered daily by subcutaneous injection during the period of active growth and can be continued into adulthood. 9 Children with short stature due to Turner syndrome and chronic renal insufficiency also are treated with GH. Growth hormone therapy may also be considered for children with idiopathic short stature. 10 In a rare condition called Laron-type dwarfism there is an extreme resistance to GH due to abnormalities in the growth hormone receptor. 9,14 Affected persons tend to be obese and have high levels of GH and low levels of IGF-1. The condition is seen predominantly in people of Mediterranean descent, especially Sephardic Jews. FIGURE 32-2. Child with growth hormone deficiency. A 5.5-year-old boy (left) with growth hormone deficiency was significantly shorter than his fraternal twin sister (right), with the discrepancy beginning early in childhood. Notice his chubby, immature appearance compared with his sister. (From Shulman D, Bercu B, volume eds. Atlas of Clinical Endocrinology, Volume IV: Neuroendocrinology and Pituitary Disease. Korenman S, series ed. Philadelphia, PA: Current Medicine; 2000. With kind permission of Springer Science + Business Media.)