Dr. YK Amdekar writes on a common issue that physicians come across in their practice-- short stature. The underlying causes could be varied, hence requiring thorough investigation before choosing therapy.

To read other originals by Dr. YK Amdekar, click here.

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Introduction

Height (of) achievement is always a dream and hence short stature in a child is a concern for parents. Length/height depends upon nutrition in infancy, thyroid and growth hormone beyond infancy in childhood and sex hormone during adolescence besides genetic factors. Once puberty is achieved, growth nearly stops but timing of puberty varies in individuals. If puberty is delayed, it ends in tall stature while if puberty is achieved early, it results in short stature. Girls active in sports tend to achieve puberty bit later than those who tend to be sedentary.

In an adequately nourished infant with normal status of thyroid function, growth hormone and sex hormone, height will be decided by genetic factors alone and it cannot be changed. Thus, a child of short parents is most likely to be short. It is a myth that height increases with pull-ups or any other exercises or supplements.

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Is there any difference between length and height? How are they measured?

For practical purposes, both are nearly equal though length is slightly more than height. This is because, on standing, there is a small reduction in intervertebral spaces. Measuring length or height accurately is not as simple as one thinks.

1. For accurate measurement of height, the person must stand erect with occiput, buttocks, and heels touching against steadiometer (ruler on a stand) and horizontal headpiece resting on head.
2. Length is measured with infant lying supine on an infantometer (horizontal ruler with a movable foot-end piece) with head placed at one end and foot-end moved to touch heels with outstretched legs.

Ideally, measurement is considered accurate only if three consecutive readings are same. However in routine practice, single reading suffices as interpretation does not vary significantly. Though for research purposes, accuracy is vital.

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Average length/height gain in childhood

An infant gains 25 cm in length in the first year of which 15 cm is gained in the first 6 months and 10 cm in the latter half of the first year. In the second year, length is increased by 12 cm and thereafter 5 to 6 cm per year until adolescence. During adolescence, height increases by 10 to 12 cm per year. There are many variables and so even normal children grow at different velocity.

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Can adult height be predicted in childhood?

In a normal healthy child, Tanner formula can roughly predict adult height taking into account mid-parental height with a range of 8.5 cm on either side.

Target height = (father’s height + mother’s height) divided by 2 + 6.5 cm for boys and minus 6.5 cm for girls with a range of 8.5 cm upwards or downwards.

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Confirm short stature

Height below 3rd centile on the growth chart or 2nd standard deviation below the mean for that age is considered short stature meaning the child is short in height. The best way to judge is to monitor height velocity over time period or to follow the trend of height gain. It is only when short stature is confirmed that one must try to find out the probable cause.

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Common causes of short stature

Early onset of chronic malnutrition is the most common cause especially in the underprivileged community. In such a situation, the child will never attain normal adult height. Other pathological causes include Cushing’s, hypothyroidism and growth hormone deficiency, syndromic abnormalities (Down, Noonan, Russell-silver, Prader-Willi and Turner syndrome in girls), chronic systemic diseases, chondrodystrophy such as achondroplasia and rickets. In the absence of any such pathology, short stature may be genetic or constitutional. A child with constitutional short stature does attain normal adult height with a spurt in height gain during adolescence while a child with genetic short stature does remain short in the adult life.

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Clinical approach to short stature

The first step is to confirm short stature. Parents often compare growth of their children with those of the peers or other children in extended families. Even two children of the same parents vary in their growth pattern. Once short stature is confirmed, it is important to find out time period of origin of the problem.

1. If it has started very early in life, it is mostly primary nutritional or at times secondary nutritional due to severe systemic diseases. Child with systemic disease resulting in short stature will be sick-looking with many other symptoms and signs besides short height.
2. Most of other conditions presenting with short stature are not sick.
3. Growth hormone deficiency typically presents after the age of 3-4 years of age.
4. Delayed cognition is typical of hypothyroidism along with abnormal facies and are also in mucopolysaccharidosis with hepatosplenomegaly and bony defects. Bony defects are typical features of chondrodystrophy and rickets.
5. Abnormal facies, delayed development and structural malformations in different organs are features of syndromic problems.
6. Proportionate or disproportionate trunk and limbs may help in assessing bony abnormalities.
7. In the absence of any of the above-mentioned abnormalities, short stature may be genetic or constitutional.

Assessment of mid-parental height and periodic growth monitoring including height velocity would help differentiating one from the other.

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Investigations in a child with short stature

1. Bone age is estimated radiologically by Tanner-Whitehouse method that can report bone age in weeks. Routine X-ray of bones fails to assess bone age correctly as it can at best offer a range in years that is not useful. Age denotes bone development or maturity.
2. Height age is the age at which a normal child achieves the said height. It denotes bone growth. For example, if a 6-year-old child has a height of 100 cm, then his height age is 4 years because a normal child attains 100 cm at 4 years of age.
3. Chronological age is the actual age in years and months. Comparing chronological age with bone and height age and assessing height velocity gives a clue to probable diagnosis.

Age is delayed in hypothyroidism and growth hormone deficiency and may be mildly delayed in malnutrition.

1. If chronological age is more than height age, which is more than bone age, it suggests hormonal deficiency that can be further proved by specific tests. In fact, hypothyroidism should be suspected at birth by cord blood test for TSH and further confirmed by free T4. Early detection of hypothyroidism is important to avoid delayed brain development as thyroid supplements can be started before brain function is affected.
2. If chronological age is equal to height age but more than bone age, it is likely to be genetic or due to small birth weight for gestational age (both the conditions have normal height velocity) or chromosomal disorder (abnormal height velocity). If bone age and height age are equal but less than chronological age, it is likely to be constitutional (normal height velocity) or chronic diseases (abnormal velocity).

Once a probable diagnosis is made, specific tests can be planned to confirm the diagnosis.

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Management of short stature

There are no supplements or physical exercise that increases height. So, management depends on the cause.

1. Growth hormone replacement therapy is now freely available and would help a child with GH deficiency. It is also approved for idiopathic short stature and in children with some of the syndromic problems such as Turner syndrome in girls. It may also be useful in severe systemic diseases with growth failure.
2. Thyroid replacement should start at the earliest as mentioned above.
3. Vitamin D deficiency rickets can be treated with Vitamin D supplements.
4. Systemic diseases may have specific treatment if available.

In summary, short stature is best assessed by periodic monitoring of growth and plotted on a standard chart. It helps to pick up early deviation in growth parameters and would lead to rational management if possible. Treatable conditions should not be missed and in particular, hypothyroidism is best diagnosed at birth with cord blood screening. Growth hormone replacement is now possible and economically affordable. After all, height (of) achievement is everyone’s aim in life.

Disclaimer- The views and opinions expressed in this article are those of the author's and do not necessarily reflect the official policy or position of M3 India.