THE CHILD WITH SHORT STATURE

THE CHILD WITH SHORT STATURE

Deflation

Short stature is defined as length/height

1. Below 3^rd percentile for age or
2. Below more than 2 standard deviation (SD) of mean forage

In addition, the height velocity is usually < 25^th percentile for age.

Etiology

Short stature is a common pediatric problem. Most enlightened parents are keen to know if their child, who had not been keeping pace with the healthy peers of his age, “ is leading for dwarfism.” Obviously, the doctor must evaluate the child fully, bearing in mind that a large number of etiologic factors cal lead to short stature.

Short stature may be primary or secondary. Primary short stature is usually due to an intrinsic defect in the skeletal system as a result of some genetic or prenatal damage (say, IUGR). Here, potential for normal bone growth is impaired through skeletal age is unaffected. Main affect is on diaphyseal growth.

Secondary short stature is characterized by impairment of bone age and height to the same extent. Here, the potential for reaching the adult height is subject to availability of proper treatment.

Diagnostic approach

Evaluation should be based on a good history and physical examination, routine investigation, bone age and study of growth rate. Hormonal studies and Karyotyping are needed in selected cases.

In anthropometry, height velocity is more useful than a single recording of the height. It is calculated from at least two accurate readings at a gap of 6 months (preferably one year). A velocity of less than 4 cm per year between 5 years of age and adolescence is considered pathologic. For younger children, it varies with age: 15 cm for 0 to 6 months, 7 cm for 6 to 12 months, 10 cm for 1 to 2 years, and 5 cm for 2 to 5 years.

Body proportion are considered to be most accurate index of height. Upper segment/lower segment ratio is increased in hypothyroidism and short-statured dwarfism(achondroplasia).

Measurement from midfinger tip to midfinger tip (span)is case of fully outstretched arms and hands is increased(more than height) in spondyleopiphyseal dysplasia (Morquio disease)

Measuring parent’s  height is of value. The so called midparental height, a genetic component, gives the subject’s target height. It is determined as mean of father and mother’s heights plus 13 in case of boys and minus 13 in case of girls.

If weight is less proportionally reduced than height, nutritional deprivation must be seriously considered. On the contrary, if weight is nearly normal but height is significantly less, hypothyroidism must be seriously considered. Growth hormone deficiency and hypercorticism is also figure in the differential diagnosis.

Children with delayed puberty and short stature should arouse suspicion of sex chromosomal anomalies such as Turner syndrome. Here stature, despite timely onset of puberty, is likely to end up with short stature. In “late maturers”, both short stature and delayed puberty coexist. These latematures ultimately attain better height compared to early maturers.

Bone age, assessed through radiologic examination of certain bones and then comparing the appearance and fusion of epiphyseal centers with standard normal radiographs for different ages, is of considerable value. In infancy, knee, wrist and hand and in later yars elbow, wrist and hand are appropriate sites.

With the availability of assessment mentioned so far, the following guidelines are suggested.

1. If height age falls within 2 years of the chronologic age, the subject need not be considered to have short stature.
2. If height is less than the chronologic age and the bone age equal to height age, slow growth – in other words constitutional delay- is the likely cause of short stature. In this situation, the child may well to attain his normal height subsequently.
3. If the height age is less than the chronologic age and the bone age equal to chronologic age, genetic short stature is the diagnosis. Such a child has short parents and is likely to remain short.
4. If bone age is less than chronologic age, one should consider constitutional growth retardation, hypothyroidism, malnutrition, growth hormone deficiency and chronic systemic disease as the cause of short stature. Besides radiology and routine investigations, including meticulous stool examination on at least 3 successive days, it should be ascertained if there is need for intensive workup. The indications for  such a workup include

-          Height over 2SD less than the mean for that age

-          Growth (height) velocity less than 4 cm per year.

-          Growth centile showing subnormality in relation to family stature (midparental height)

5. Inappropriate bone age compared to height age and actual (chronologic) age

-          Existence of characteristic features of an endocrinal cause or a syndromal

State

Specific investigations include:

1. Buccal smears
2. Thyroid function tests
3. Somatomedin-C measurement
4. Cortisol, LH, FSH, PRL, testosterone, estrogen levels
5. Urinary iodine levels
6. Complete Karyotyping
7. Malabsorption studies
8. Renal acidification test
9. Urinary aminoacidogram
10. Imaging studies like ultrasound, CT scan (pituitary, adrenals, pelvic organs).

Management

Even if no treatable cause is found , the situation should be explained to the parents. Only established indication for growth hormone therapy is growth hormone responsiveness in case of:

1. Biochemical GH deficiency supported by stimulation tests, after thyroid function has been shown to be normal, plus slow growth velocity, and
2. Slow growth velocity in idiopathic short stature.

Today’s genetically engineered GH i.e. recombinant human GH (rhGH) therapy costs US$ 4000 to 8000. It is mandatory to start such a therapy before 11 years of age for attaining the optimal height. Recombitant GH is administered in a daily dose of 0.1 unit/kg (SC), preferably at night, until adult height is attained. Usually height gain is 10-12 cm in first year and 6-8 cm every year subsequently. More recently, it has been advocated that GH therapy should preferably be monitored by insulin-like growth

Factor-1(IGF-1) to ensure safety and efficacy of GH. Excess GH and IGF-1 exposure and malignancy are known risks of GH therapy.

Obesity

Despite overwhelming problem of nutritional deficiencies in developing countries, obesity too is encountered, especially among the infants and children of the elite who ape the lifestyle of the west.