Cover article

Understanding growth patterns in short stature

By Ronald C. Samuels, MD, MPH, and Laurie E. Cohen, MD

Children who are short are generally growing normally, but short stature can be the sign of an underlying disorder. Here's how to tell the difference between what's meant to be and what isn't.

Jennifer Johnson is brought to your office shortly after her 9th birthday for a well-child exam. She and her parents have just relocated to your area from the other side of the country, and this is their first visit. Their main concern is that Jennifer is short. She is 120 cm (47 inches) tall. Is something wrong with Jennifer?

This scenario is familiar to most pediatricians. To assess the need for further evaluation or referral, you must be able to discriminate normal from pathologic growth. Using Jennifer as a model, we will review how to confirm whether her short stature is genetic or familial, as is most common, or whether it is a sign of an underlying medical problem.

Start with the basics

Your first step naturally will be to plot Jennifer's height on a standardized growth chart, just as you do for every child. Most pediatricians use growth charts developed by the National Center for Health Statistics (NCHS) in 1977. The NCHS and the Centers for Disease Control and Prevention (CDC) recently updated these charts, which were released last year. The old charts were based on data collected in a private Ohio study and reflected growth patterns of white, middle-income, formula-fed infants.¹ In addition, the smoothed percentiles did not extend beyond the 5th and 95th percentiles or beyond the 18th brithday.^1,2

On the new charts that many pediatricians will use, the outer limits of the curves are still at the 5th and 95th percentiles. Also available, however, are charts with curves at the 3rd and 97th percentiles, which are suitable for charting the growth of very short or tall children. These are the charts reproduced for the figures in this article.

The old infant charts for birth through 3 years of age were based on data from the Fels Research Institute. The Fels data presented several problems. Distributions of birth weights did not match current national data because the Fels percentile values for birth weight were lower than the current national birth weight distributions by about 125 g at the median. The measuring procedures resulted in differences between recumbent length and stature that are probably too large. A systematic overestimation of recumbent length resulted in a downward shift in the child's placement on the growth chart when the change is made from recumbent length to stature charts.² Last, Fels data from birth to age 3 years were derived mainly from formula-fed infants, whose pattern of growth generally differs from that of breastfed infants, who grow and gain weight slightly faster than their bottle-fed peers during the first two to three months of life.² This growth steadily falls off after 3 months of age, however, and by 6 months the breastfed baby weighs less and is shorter than his or her bottle-fed peers.³

The updated growth charts are based on data gathered through 1994 from five national health examination surveys and five supplementary data sources. These data are racially and ethnically diverse and include breastfed and formula-fed infants.¹ Preterm and very low birth-weight (<1500 grams) infants from birth to age 3 years were excluded from the charts because their growth differs from that of full-term infants of higher birth weight.² The charts for older children extend to the age of 20 years. Body mass index charts are also available.¹ For more information on the available growth charts and how to obtain them, see "A new era in growth charts" below.

How children grow

Our patient Jennifer is just below the 3rd percentile for height (Figure 1). With the older growth charts, all you would know is that she is below the 5th percentile for height. Now, with 3rd percentile information readily available, we are aware that she has short stature, defined as height below the third percentile for age.⁴ The next step is to obtain early growth data for Jennifer and examine her growth velocity.

Infants grow rapidly soon after birth, about 25 cm (10 inches) in the first year of life. Growth declines progressively to about 12 cm (5 inches) during the second year and then to 8 cm (3 inches) during the third.⁵ From 3 years of age until the onset of puberty, linear growth is at a relatively stable rate of 4.5 cm (1³/₄ inches) to 7 cm (2³/₄ inches) per year.^4,5 A small linear growth deceleration may be seen before puberty begins. In general, girls begin their growth spurt earlier in pubertal development than boys do and have a smaller yearly peak height velocity—8.3 cm (3¹/₄ inches) compared with 9.5 cm (3³/₄ inches) in boys.⁵

Most children establish a pattern of growth by 3 years of age from which they do not deviate until entering puberty. During those first three years children may cross growth channels, however, because birth size is related to maternal factors whereas size later in life is related to genetic factors. When a young child is crossing percentiles downward, it is vital to take a complete history and conduct a physical exam to differentiate failure to thrive from normal "channeling." During puberty, children may again cross growth channels, depending on when their pubertal growth spurt occurs in relation to the average population. When patients between the age of 3 years and puberty change growth channels, however, they should be evaluated for a potential growth problem. First, rule out measurement errors and inaccurate plotting of measurements. Then, as described below, determine whether the child is healthy and on track for attaining adequate adult height.

Right on track

When Jennifer next visits your office you have received her previous growth data. It shows that she has always tracked around the 3rd percentile for both height and weight, a sign of health (Figure 2). Her recent growth velocity, at a rate of 5 cm (2 inches) a year, is normal.

It is important also to determine Jennifer's parents' heights and pubertal patterns. Her mother is 150 cm (59 inches) and had menarche at 12¹/₂ years, an average age. Her father is 163 cm (64 inches) tall and began puberty at an average age. Because both parents are at the 3rd percentile for height, the patient likely has familial, or genetic, short stature. This condition is characterized by a family history of short stature, normal birth length and weight, height ¾ 3rd percentile for chronologic age, a normal annual growth rate, predicted adult height ¾ 3rd percentile, normal onset of puberty, and no other cause of growth failure.⁵

To confirm that Jennifer's height is appropriate for her family, calculate a midparental height. For girls, midparental height is (mother's height + father's height - 13 cm) /2; for boys, (mother's height + father's height + 13 cm) /2. The child's target height is the midparental height +/- two standard deviations (10 cm, or 4 inches).⁵ This patient's midparental height is 151 cm (59¹/₂ inches). It is at the 3rd percentile, exactly where she is tracking.

If the patient's mother had menarche at 15 years (late) and her father was a "late bloomer" who continued to grow after graduation from high school, you might suspect constitutional delay. This condition is characterized by a slowing of growth during the first two to three years of life but a normal or low-normal annual growth rate thereafter. There is a family history of a similar pattern of growth and delayed puberty. When you suspect constitutional delay, the next step is to evaluate bone age, as you would whenever a child has poor growth.

Bone age is determined with a plain radiograph of the left wrist and hand. Epiphyseal ossification of the bones is compared with established standards with regard to size and shape.⁶ Most conditions that cause poor linear growth, such as malnutrition, hypothyroidism, and growth hormone deficiency (discussed later), also cause a delay in skeletal maturation and a retarded bone age.⁵ In constitutional delay, bone age lower than chronologic age reflects increased growth potential that will result in a normal predicted adult height in the context of the family pattern.⁴ Figure 3 shows Jennifer's growth data if her short stature was associated with constitutional delay. Her bone age is 6 years 10 months. Her height, 120 cm (47 inches), is at the 50th percentile for that age.

In Figure 4, which again shows a girl with short stature, the bone age is equal to the chronologic age. If Jennifer's mother is 167 cm (66 inches) and her father is 180 cm (71 inches), the midparental height is 167 cm (66 inches). Jennifer's predicted height based on her bone age is 145 cm (57 inches), more than two standard deviations below the midparental height. Because her growth rate is normal, it is unlikely that systemic illness is the reason for her short stature.

To investigate the possibility that intrauterine growth retardation (IUGR) is the cause, a careful prenatal history should be obtained, including maternal malnutrition and substance abuse, congenital infections, multiple gestations, and placental insufficiency. IUGR is most commonly defined as a birth weight below the 10th percentile for the gestational age. As many as 70% of infants who are small for gestational age are constitutionally small fetuses expressing their genetic potential. In the remaining 30%, however, growth is restricted because of various pathologic conditions. Fifteen percent to 20% of infants with IUGR will have short stature by the age of 4 years, and 7.9% will still be short at 18 years of age.⁷ If the history is not consistent with IUGR and if no other explanation can be found for Jennifer's proportionate short stature, idiopathic short stature would then be the diagnosis of exclusion.

When to suspect a genetic syndrome

Let's suppose Jennifer had a normal height gain from birth until 3 years of age, after which her growth velocity declined progressively (Figure 5, left). She has a history of recurrent otitis media. Her mother is 167 cm (66 inches) and her father is 180 cm (71 inches). A physical examination reveals multiple nevi, a low posterior hairline, webbed neck, broad chest with widely spaced nipples, short fourth metacarpals, and increased carrying angle of the arms (cubitus valgus). These phenotypic features are characteristic of Turner syndrome.⁸

Plotting Jennifer's height on a Turner syndrome growth chart reveals growth along the 75th percentile (Figure 5, right). Parental height and the height of girls with Turner syndrome are positively correlated; hence, Jennifer's height is at the 75th percentile on the Turner chart, about the same percentile as her midparental height, according to normal standards.⁹ Consider Turner syndrome in any girl with unexplained short stature and no history of familial short stature. Characteristic phenotypic features may not be present. A definitive diagnosis is made with chromosomal testing. A buccal smear is not recommended because discrimination and specificity are inadequate.¹⁰

Because many girls with Turner syndrome have streak gonads and ovarian failure, a follicle-stimulating hormone (FSH) level should be obtained after the age of 10 years.¹¹ As many as 10% to 20% of patients will still secrete some ovarian estrogen during late childhood and early adolescence.¹² In addition, many of these girls have autoimmune thyroiditis with subsequent development of hypothyroidism.¹² Thyroid-stimulating hormone (TSH) levels should therefore be obtained annually. Also evaluate for structural abnormalities of the kidneys and ureters, which are found in 22% to 40% of patients, and for cardiac lesions, present in about one third.^{10, 12}

Many other congenital disorders are commonly associated with short stature. Specialty growth charts have been created for tracking other specific syndromes, such as Down and Noonan syndrome.

Systemic disorders also a possibility

Figure 6 shows that Jennifer had been growing along the 25th percentile until age 7, after which her growth progressively fell off. Her weight also had been progressing along the 25th percentile until age 6, but because she has gained little weight she is underweight for height. Her past medical history is unremarkable, as is her diet history, which reveals adequate caloric intake. She denies headaches, change in vision, nausea, vomiting, diarrhea, or abdominal pain. Her physical exam is unremarkable.

A decreased weight-to-height ratio generally indicates a systemic illness (Table 1). Absolute or relative nutritional deficiency from malnutrition, anorexia nervosa, malabsorption, inflammatory bowel disease (IBD), celiac disease, or diabetes mellitus typically results in decreased linear growth that is preceded by a decline in the rate of weight gain or in a weight loss. IBD and celiac disease may present with growth retardation, although the child is otherwise completely asymptomatic. Therefore, a negative review of systems and a physical exam do not exclude these conditions.⁵

TABLE 1
Why is the child short?

Systemic illnesses
Hypocaloric
  Malnutrition
  Gastrointestinal disease (malabsorption
    inflammatory bowel disease,
    celiac disease)
   Poorly controlled diabetes mellitus
Metabolic
  Renal (renal tubular acidosis
    nephrogenic diabetes insipidus
    renal failure)
  Hepatic
  Cardiac (cyanotic heart disease)
  Hematologic (chronic anemias)
  Respiratory (cystic fibrosis, severe
    asthma [hypoxemia])
  Chronic infections

Endocrine disorders
Hypothyroidism
  Congenital
  Acquired
Glucocorticoid excess
  Exogenous steroid use
  Endogenous
Growth hormone deficiency
  Isolated
  Multiple hormonal deficiencies

Renal disease, including renal tubular acidosis, nephrogenic diabetes insipidus, and renal failure, can also present with poor linear growth. Renal tubular acidosis and nephrogenic diabetes insipidus may be present from birth and manifest as "failure to thrive."⁵ In other chronic illnesses, such as cyanotic heart disease, growth is impaired because increased energy expenditure is associated with the disease.⁵

When you suspect systemic illness, order a laboratory screening to rule out chronic disease. This evaluation includes a complete blood count (CBC) to screen for infection, anemia, and other hematologic abnormalities; erythrocyte sedimentation rate (ESR) to screen for evidence of chronic inflammation, such as IBD; electrolytes and a chemistry panel to screen for abnormalities of the kidneys, liver, and bones; urinalysis to screen for kidney disease, as well as renal tubular acidosis in infants; and anti-endomysial antibodies with an immunoglobulin A level to screen for celiac disease. Perform other laboratory evaluations only as the history and physical examination indicate.

Is it an endocrine disorder?

Figure 7 shows that, between the ages of 7 and 9 years, Jennifer's height has fallen from the 25th percentile, while her weight, 26 kg (57 pounds), still is at the 25th percentile. Her bone age is delayed at 7 years, 4 months, an indication that she has a condition that causes poor linear growth. Jennifer is complaining of fatigue, dry skin, and constipation. Her physical exam reveals a sallow appearance, dry skin, and coarse hair.

Preserved weight gain or frank obesity associated with poor linear growth (being overweight for height) suggests an endocrine disorder.⁵ In this patient, a TSH level confirms the diagnosis of primary hypothyroidism. Onset of symptoms and signs (including cold intolerance, myxedema, and delayed deep-tendon reflexes) may be subtle. An overtly enlarged thyroid gland may not be present. Once treatment with L-thyroxine is initiated, growth velocity increases rapidly. A permanent height deficit caused by the long period of thyroid hormone deficiency before treatment began may remain, however.¹³

Figure 8 below shows that our patient's height has been crossing percentiles downward since early childhood (we know her birth length and weight were normal). At the same time, she is becoming progressively overweight for height. In addition to appearing somewhat "chubby," she has a high-pitched voice. Her physical exam is otherwise unremarkable. Because of Jennifer's poor growth rate, laboratory screening for systemic disorders, as well as a TSH level, are performed. All tests are within normal limits.

Because other disorders affecting growth have been ruled out, growth hormone (GH) deficiency must be considered. Measuring the GH level at random is not useful because growth hormone is secreted in a pulsatile manner and serum levels are generally low between pulses. Obtaining levels of insulin-like growth factor-1 (IGF-1), which mediates the growth-promoting actions of GH, and of IGF binding protein-3 (IGFBP-3), the major carrier protein for IGF-1, are helpful because their concentrations parallel the secretion of growth hormone. IGF-1 concentrations are markedly age dependent, however, and, in young children, the normal range drops so low it overlaps the range for GH deficiency.¹⁴ Low levels of IGF-1 may also be seen in malnutrition, hypothyroidism, and chronic renal and liver disease.⁴ Although IGFBP-3 levels are less age dependent and less nutrition dependent than levels of IGF-1, low levels of the protein may be seen in chronic malnutrition.¹⁴ If these screening tests suggest GH deficiency, refer the child to a pediatric endocrinologist for further evaluation.

Children with partial GH deficiency usually present after 6 months of age, when the influences of maternal hormones wane. They tend to have increased periabdominal fat and decreased muscle mass. Other features of this condition include delayed dentition, thin hair, poor nail growth, and a high-pitched voice.

Severe GH deficiency in the newborn period may be characterized by hypoglycemia and conjugated hyperbilirubinemia, as well as a small phallus in boys, consistent with multiple anterior pituitary hormone deficiencies. Hypopituitarism may be associated with other midline facial and central nervous system abnormalities. Injuries of the hypothalamus and pituitary, including infiltrative and autoimmune disease or suprasellar tumors, can result in hypopituitarism. Surgical resection and cranial irradiation of these lesions may also cause hypopituitarism.⁴ Genetic causes of GH deficiency include mutations in the GH gene or receptor or in other pituitary developmental factors.¹⁵

Putting it together

Short stature is a common clinical problem. It is a symptom, not a disease. Any child with an abnormally slow growth rate, downward crossing of percentile channels on the growth chart after the age of 18 months, height below the 3rd percentile, or height significantly below the genetic potential (two standard deviations below midparental height) deserves further evaluation. (See "What to look for when watching a child grow," below.) Delay in diagnosis and initiation of treatment of an underlying disorder may result in failure to achieve the genetic potential in height. If you are uncertain about the diagnosis or suspect an endocrinopathy, refer the patient to a pediatric endocrinologist.

REFERENCES

1. Zanzola L: Revised pediatric growth charts available from CDC, Academy. AAP News, July 6, 2000

2. Kuczmarski RJ: Revised growth charts due in late '98. AAP News, Sept 7, 1998

3. Rider E, Samuels R, Wilson K, et al: Physical growth, infant nutrition, breastfeeding, and general nutrition. Curr Opin in Pediatr 1996;8:293

4. Shulman DI: Growth hormone therapy: An update. Contemporary Pediatrics 1998;15(4):95

5. Vogiatzi MG, Copeland KC: The short child. Pediatrics in Review 1998;19:92

6. Oestreich AE: Skeletal maturation, in Kirks DR (ed): Practical Pediatric Imaging, ed 2. Boston, Little, Brown and Co, p 266

7. Botero D, Lifshitz F: Intrauterine growth retardation and long-term effects on growth. Curr Opin Pediatr 1999;11:340

8. Jones KL: XO syndrome (Turner syndrome), in Smith's Recognizable Patterns of Human Malformations, ed 5. Philadelphia, WB Saunders Co, 1997, p 81

9. Massa GG, Vanderschueren-Lodeweyckx M: Age and height at diagnosis in Turner syndrome: Influence of parental height. Pediatrics 1991;88:1148

10. Doherty L, Brown DM, Ainslie M, et al: Turner syndrome practice guidelines. Endocrinologist 1997;7:443

11. Saenger P: Clinical review 48: The current status of diagnosis and therapeutic intervention in Turner's syndrome. J Clin Endocrinol Metab 1993;77:297

12. Rosenfeld RG: Turner syndrome: A guide for physicians, ed 2. The Turner's Syndrome Society, 1992

13. Rivkees SA, Bode HH, Crawford JD: Long-term growth in juvenile acquired hypothyroidism: The failure to achieve normal adult stature. N Engl J Med 1988; 318:599

14. Rosenfeld RG, Abertsson-Wikland K, Cassorla F, et al: Diagnostic controversy: The diagnosis of childhood growth hormone deficiency revisited. J Clin Endocrinol Metab 1995;80:1532

15. Cohen LE, Radovick S, Wondisford FE: Transcription factors and hypopituitarism. TEM 1999;10:326

DR. SAMUELS is an instructor in pediatrics at Harvard Medical School and assistant in medicine (general pediatrics) at Children's Hospital, Boston.

DR. COHEN is an instructor in pediatrics at Harvard Medical School and assistant in medicine (endocrinology) at Children's Hospital, Boston.

A new era in growth charts

The Centers for Disease Control and Prevention (CDC) and the National Center for Health Statistics (NCHS) released new growth charts on May 30, 2000. Some of the charts were revised, corrected, and reissued later the same year because of errors in graphing. Charts can be downloaded at www.cdc.gov/growthcharts . The charts are available in two sets and include a new method of assessment for body mass index (BMI):

Set 1: Clinical charts with 5th and 95th percentiles

Birth to 36 months

Boys: Length-for-age and weight-for-age (revised)
Boys: Head circumference-for-age and weight-for-length
Girls: Length-for-age and weight-for-age (revised)
Girls: Head circumference-for-age and weight-for-length

Children 2 to 20 years

Boys: Stature-for-age and weight-for-age (revised)
Boys: BMI-for-age
Girls: Stature-for-age and weight-for-age (revised)
Girls: BMI-for-age
Boys: Weight-for-stature
Girls: Weight-for-stature

Set 2: Clinical charts with 3rd and 97th percentiles

Birth to 36 months

Boys: Length-for-age and weight-for-age (revised)
Boys: Head circumference-for-age and weight-for-length
Girls: Length-for-age and weight-for-age (revised)
Girls: Head circumference-for-age and weight-for-length

Children 2 to 20 years

Boys: Stature-for-age and weight-for-age (revised)
Boys: BMI-for-age
Girls: Stature-for-age and weight-for-age (revised)
Girls: BMI-for-age
Boys: Weight-for stature
Girls: Weight-for-stature

The CDC and NCHS note that the charts in both sets are intended to be printed as two-sided copies. For infants: Side 1—length-for-age and weight-for-age; side 2—head circumference-for-age and weight-for-length. For children: Side 1—stature-for-age and weight-for-age; side 2—either BMI-for-age or weight-for-stature (2-5 years of age only). Charts in each of the sets also can be accessed through a summary file of each set. Hard copies of these charts also can be purchased from the American Academy of Pediatrics. Many specialty growth charts, including those for Down and Turner syndromes, also are available from the American Academy of Pediatrics ( www.aap.org ).

Source: www.cdc.gov/growthcharts

What to look for when watching a child grow

Growth abnormalities may be the first sign of an underlying disorder, and the differential diagnosis for short stature or poor growth is wide. Keep in mind the following guidelines for monitoring growth.

• Assess the child's height in the context of the growth pattern (velocity) and family history (parental heights and pubertal patterns).

• A normal growth rate along a percentile consistent with parental heights suggests familial or genetic short stature, while a similar scenario with a delayed bone age and a family history of delayed puberty suggests constitutional growth delay.

• Being underweight for height raises the suspicion of a systemic illness, and initial screening tests might include a chemistry panel, CBC, ESR, and anti-endomysial antibodies with an IgA level; further screening should be guided by history and physical exam.

• Being overweight for height suggests an endocrine disorder. Initial screening tests might include a full set of thyroid function tests (the TSH level may be inappropriately "normal" in central hypothyroidism) and IGF-1 and IGFBP-3 levels.

• Consider a genetic syndrome if the patient has dysmorphic features. Turner syndrome must be ruled out in any girl with unexplained short stature.

 

Ronald Samuels, Laurie Cohen. Understanding growth patterns in short stature. Contemporary Pediatrics 2001;6:94.