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Growth Physiology

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Growth Physiology

  • See Also
  1. Delayed Growth
  2. Failure to Thrive
  3. Height Measurement in Children
  4. Weight Measurement in Children
  5. Short Stature
  6. Tall Stature
  • Physiology
  • Primary Growth Determinants by Age
  1. Newborn to 2 years
    1. Intrauterine environment
    2. Catch up growth (6 to 18 months)
    3. By age 2 years, children reach their genetically programmed growth percentile (based on mid-parental height)
  2. Age 2 years old to Puberty
    1. Growth Hormone mediated growth
    2. Children should follow a percentile on growth chart (within 2 large percentile bands)
  3. Adolescents (peri- and post-Puberty)
    1. Sex Hormones
  • Physiology
  • Nutrition, Intake, and Absorption Requirements for Growth
  1. Adequate Total Calorie Intake
  2. Amount and Quality of Protein (Essential Amino Acids)
  3. Adequate bile salts for fat absorption
  4. Minerals (growth regulation)
    1. Calcium
    2. Zinc
    3. Copper
  5. Adequate Gastrointestinal function
    1. Adequate gastrointestinal mucosal surface
    2. Adequate gastrointestinal motility
    3. Adequate digestive enzymes
      1. Stomach and duodenum
      2. Pancreas enzymes
  • Physiology
  • Hormonal factors related to Growth
  1. Vitamin D (ingested or produced)
    1. Metabolized in liver and Kidney to active form
    2. Important for Calcium absorption for bone growth
    3. Primarily affects growth when deficient (Hypovitaminosis D, Rickets)
      1. However, when Vitamin D is at normal levels (supplementation does not increases linear growth)
  2. Pituitary Growth Hormone (GH)
    1. Regulated by Hypothalamus
    2. Thyroid Hormone critical for Growth Hormone secretion
    3. Growth Hormone action
      1. Requires adequate Caloric Intake and Insulin
      2. Growth Hormone released from pituitary
      3. Growth Hormone reaches liver and other tissues
      4. IGF-I synthesized
        1. Insulin-like Growth Factor or Somatomedin C
        2. IGF-I stimulates cartilage proliferation
        3. Affects Growth Plate long bones
  3. Sex Hormones
    1. Initially stimulate growth (esp. with onset of Puberty)
    2. Later halt growth
      1. Fuses epiphysis to diaphysis of long bones
  • Physiology
  • Genetic factors related to growth
  1. Parental Height
    1. See Midparental Height
    2. Tall parents are >2 SD above normal adult parental height for gender, ethnicity/nationality
    3. Short parents are <2 SD below normal adult parental height for gender, ethnicity/nationality
  2. Abnormalities
    1. Chromosomal abnormalities
    2. Osteochondrodystophies