The factors responsible for postnatal growth are not the same as the factors that mediate fetal growth. Thyroid hormone is essential for normal postnatal growth, although a thyroid hormone–deficient fetus achieves a normal birth length; similarly a GH-deficient fetus has a normal birth length, although in IGF-1 deficiency resulting from GH resistance (Laron dwarfism), fetuses are shorter than control subjects. Adequate thyroid hormone is necessary to allow the secretion of GH. Hypothyroid patients may appear falsely to be GH deficient; with thyroid hormone repletion, GH secretion normalizes. Gonadal steroids are important in the pubertal growth spurt. The effects of other hormones on growth are noted in Table 173-1.
Short Stature of Nonendocrine Causes
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Short stature is defined as subnormal height relative to otherchildren of the same gender and age, taking family heightsinto consideration. It can be caused by numerous conditions(Table 173-2). The Centers for Disease Control and Prevention growth charts use the 3rd percentile of the growth curve as the demarcation of the lower limit. Growth failure denotes a slow growth rate regardless of stature. Ultimately aslow growth rate leads to short stature, but a disease processis detected sooner if the decreased growth rate is noted beforethe stature becomes short. Plotted on a growth chart, growthfailure appears as a curve that crosses percentiles downwardand is associated with a height velocity below the 5th percentile of height velocity for age (Fig. 173-1). A corrected mid-parental, or genetic target, height helps determine whetherthe child is growing well for the family (see Chapter 6). Todetermine a range of normal height for the family under consideration, the corrected midparental height is bracketed by2 standard deviations (SDs), which, for the United States, isapproximately 10 cm (4 in.). The presence of a height 3.5 SDsbelow the mean, a height velocity below the 5th percentilefor age, or a height below the target height corrected for mid-parental height requires a diagnostic evaluation.
Nutrition is the most important factor affecting growth on a worldwide basis (see Chapter 28). Failure to thrive may develop in the infant as a result of maternal deprivation(nutritional deficiency or aberrant psychosocial interaction) or as a result of organic illness (anorexia, nutrient losses through a form of malabsorption, or hypermetabolism caused
Exogenous Diabetes mellitus under poor control Diabetes insipidus (untreated) Hypophosphatemic vitamin D-resistant rickets Virilizing congenital adrenal hyperplasia (tall child, short adult)
P-450c21, P-450c11 deficiencies
Turner syndrome (syndrome of gonadal dysgenesis) Noonan syndrome (pseudo-Turner syndrome) Autosomal trisomy 13, 18, 21 Laurence-Moon-Bardet-Biedl syndrome Prader-Willi syndrome Autosomal abnormalities Dysmorphic syndromes (e.g., Russell-Silver or Cornelia
Gastrointestinal disorders Malabsorption (e.g., celiac disease) Disorders of swallowing Inflammatory bowel disease
Hereditary fructose intolerance Malnutrition Kwashiorkor, marasmus Iron deficiency Zinc deficiency Anorexia caused by chemotherapy for neoplasms Cerebral palsy
Modified from Styne DM: Growth disorder. In Fitzgerald PA, editor: Handbook of Clinical Endocrinology, Norwalk, CT, 1986, Appleton & Lange. AIDS, Acquired immunodeficiency syndrome; CNS, central nervous system; GH, growth hormone; IGF, insulin-like growth factor. *Only if caloric intake is severely diminished.