Short Stature - January 2006
Short stature is defined as standing height (or supine length) more than 2 SD below the mean (or below the 2.5 percentile) for gender. However, short stature optimally is defined relative to the genetic endowment of the individual and, particularly, the mid-parental height (MPH). A child’s predicted adult height should fall within 10 cm of his/her parents’ MPH.
For girls, MPH = [mother’s height in cm + (father's height in cm - 13)]/2.
For boys, MPH = [(mother’s height in cm + 13) + father's height in cm)]/2.
Growth rate is equally important. Children grow 23-28 cm in the first year, 7.5-13 cm/yr from 1-3 yrs, then 4.5-7 cm/yr from 3 yrs to puberty. Just before puberty, growth is about 4 cm/yr before it accelerates again as the pubertal growth spurt (8-9 cm/yr in girls and 10.3 cm/yr in boys). Girls usually continue to grow until a bone age (BA) of about 14 yrs and boys stop growing after a BA of 16. From 6-18 months, many children move up or down on their growth percentiles, but by 24 months, most children find “their” growth channel and stay on the same percentile.
It is also important to look at a child’s weight in relation to height. Overweight children are usually tall because of an accelerated growth rate. A child who is short and overweight should be evaluated.
Causes of short stature can be divided into three broad categories: 1) Chronic conditions (including under-nutrition and genetic disorders); 2) Familial short stature (also referred to as genetic or idiopathic short stature (ISS); and 3) Constitutional delay of growth and development (CDGD).
The hallmarks of familial short stature include BA appropriate for chronologic age, normal growth velocity and predicted adult height appropriate to the familial pattern. By contrast, constitutional delay is characterized by delayed BA, normal growth velocity, and predicted adult height also appropriate to the familial pattern. Patients with CDGD typically have a first- or second-degree relative with CDGD (e.g., menarche when > 15 yr, or adult height attainment when > 18 yr in males).
Endocrine diseases are rare causes of short stature. Deceleration in linear growth, occurring to a greater degree than weight loss, is a hallmark of endocrine causes of short stature. Growth hormone (GH) is required for normal growth except in the first 9-12 months of life. Children with growth hormone deficiency (GHD) are short, often look younger than their chronological age, may have a weight centile higher than their height and usually have a delayed BA. Children with GHD have a slow rate of growth and their growth curves fall away from the normal curves.
An initial evaluation for children with short stature should include the following:
1) A complete history, encompassing the child’s weight and length at birth, prior growth pattern and the final (or current) heights and weights, and the pubertal history of parents and siblings.
One’s social and developmental history are also important. Emotional deprivation can cause severe growth failure. Growth is often impaired in refugees, in children emerging from foster care or certain international adoption settings. Delayed onset of teething, for instance, can suggest hypothyroidism, under-nutrition, or simply CDGD.
2) Complete review of systems with a focus on nutrition, GI, pulmonary, immune, and renal symptomatology. Chronic use of steroids is a major cause of short stature.
3) Lab tests include T4, TSH, IGF-1, IGF-BP3, CBC, prolactin, blood chemistries, ESR, urinalysis and a karyotype (to rule out Turner’s Syndrome). Normal levels of IGF-1 and IGF-BP3 can rule out GHD but low serum IGF-1 is often found in children with inadequate nutrition or feeding problems.
4) A BA X-ray is helpful when interpreted by an experienced pediatric radiologist or endocrinologist.
5) Examination with attention to nutritional and pubertal status, midline defects, goiters, eye movements and visual fields, and signs of CNS, GI, renal, autoimmune, or genetic disorders.
Management Options
1) Chronic conditions: Familial short stature and CDGD are diagnoses of exclusion. Therefore, other chronic conditions that can affect growth must be carefully ruled out and treated as necessary.
2) Familial short stature: Most parents with short stature have short children. These children have a normal rate of growth and their growth curves run parallel to the normal growth curves. Although growing normally, these children will be short as adults, with a similar height to their parents.
3) Constitutional delay of growth and development: These children also have a normal growth velocity but will have delayed puberty, and possibly a prolonged slowdown in growth that occurs just before puberty. Their delayed BA means they will continue to grow even after other children of the same age have stopped growing. These children are reassured by family members who report being shorter than their peers throughout childhood but subsequently catching up to a normal final adult height. However, it can still be distressing for many teens to be significantly shorter and less developed than their peers. In this case, referral to a pediatric endocrinologist for evaluation and possible treatment with monthly testosterone injections to hasten the start of puberty (although it will eventually start on its own without treatments) may be emotionally beneficial.
4) Growth hormone: Children with suspected GHD should be referred to pediatric endocrinology. These include children with low serum IGF-1 and IGF-BP3, midline defects, abnormalities of other pituitary or hypothalamic function, or simply a clear deviation from their normal growth pattern. GHD is diagnosed only by abnormal GH stimulation tests which are done in a same-day admission. Documented GHD must be treated with GH. However, other conditions not associated with GHD can benefit from GH. These include chronic renal failure, Turner’s and Prader-Willi syndromes.
Despite recent FDA approval, GH treatment for children with idiopathic (or familial) short stature remains controversial. Many pediatric endocrinologists still consider such treatment medically unwarranted and risky with unknown potential long term side effects and inconclusive evidence for significant benefit after reaching final adult height. Another recent FDA approval for GH is small for gestational age (SGA). Most SGA babies “catch-up” by 6 months of age. However, about 10% of SGA infants will remain below the 3rd percentile. If they have not caught up by age 2-3 years they should be referred to a pediatric endocrinologist.
This information provided by Saleh Adi, M.D.
Director, Division of Pediatric Endocrinology and Diabetes
California Pacific Medical Center