What does your pediatrician mean when she says "short stature?" It isimportant to understand that short stature is not a specific diagnosis.Nor is it a definite indication that something is wrong with your child.Short stature is simply a descriptive term indicating that a child’s heightis less than expected for his/her age. Short stature does require evaluationby the pediatrician or family practitioner, and in some cases even a pediatricendocrinologist (a specialist that deals with glandular disorders in children).To give you a better understanding of what all of this means, the followingarticle will review the way growth is assessed in children and then describesome of the common problems identified as a result of this evaluation.
 

How We Assess Growth

Growth is one of the major characteristics of childhood and one of thebetter indicators of overall well-being in children. For this reason, duringcheck-ups, pediatricians will carefully measure the head circumferencein infants, and the height and weight of infants and children. These measuresare then compared to reference values for children of the same age, usuallyin the form of a growth chart. There is one chart for children from birthto 3 years old and another for children from 2 to 18 years old. Normalgrowth rates are different for boys and girls, so they use separate charts.

Current reference standards, in use since 1977, were derived from amixed population of healthy children through two sources: the NationalCenter for Health Statistics’ national health examination surveys for childrenage 2 to 17 years, and the Fels Research Institute in Yellowsprings, Ohio,for infants from birth to age 2 years. These charts have been adopted bythe World Health Organization for international use.

The Center for Disease Control of the US Public Health Service is currentlyin the process of revising these standards, using more data on the growthof children obtained through the national health examination surveys of1988-1994. New infant charts will be developed that reflect this nationaldata set rather than that of a single research institution’s data. Thus,within the next one to two years we will have new reference standards toapply to children’s growth.

This change in reference standard will not affect the interpretationof growth in most children. However, it will demonstrate that assessmentof growth is not absolute. It is relative. Assessment of growth is a comparisonagainst a population. In other words, when we assess growth, we are askingthe question, “Is this child behaving like other children in his population?”

Growth charts also permit us to ask whether a child continues to growaccording to the pattern she has established. Each chart has lines representingthe path of a child’s growth from a younger to an older age, plus linesrepresenting average growth rate of children versus a slower or faster,but still acceptable, rate. Each child is expected to parallel or followalong one of those lines.

Deviation from the path may be considered an abnormality when at leasttwo lines have been crossed. Thus a child may be within the lines thatdescribe normal children, yet still have a problem if his growth patterncrosses different lines. We make the diagnosis of short stature when achild is either below all the lines on the growth chart for his age (i.e.,below the fifth percentile) or that he has crossed two or more lines downfrom a previous point.
 
 

Evaluationof Short Stature

When a child is first diagnosed with short stature, it only means thatshe is shorter than the average child in her age group. It is importantto remember that short stature does not necessarily represent a diseaseprocess or even a significant problem for the child. The goal of the nextevaluation is to determine whether this short stature diagnosis representsa problem or if it is the child’s normal height.

History and physical examination: Tomake such a determination, we must obtain a complete medical and familyhistory identifying growth patterns of family members, genetic disordersassociated with poor growth, and past medical history of disease processesin the child. In addition, we perform a complete physical examination,looking for any sign of organ system failure, status of pubertal development,and physical features associated with genetic disorders.

Bone age: An important examinationinvolving an x-ray of the hand and wrist, known as bone age, is obtainedearly in the evaluation to determine the maturation of the child’s bones.Bone maturation is known to be a sensitive indicator of adverse healthexperiences in a child and can be used as a tool to predict growth potential.

Laboratory and other studies: Finally,laboratory studies are used to evaluate organ systems, such as the liverand kidneys, and glandular systems, such as the thyroid, parathyroid, adrenals,and the pituitary, whose functions are not easily assessed by a simplephysical examination. The purpose of these studies is to determine whetherthere is any organ system failure (e.g., hypothyroidism, kidney disease,cystic fibrosis) or if there are genetic abnormalities associated withgrowth disturbances (e.g., Turner’s syndrome, a disorder in females inwhich one of the two sex chromosomes is missing). If abnormalities areidentified in these first lab tests, it may be decided that more laboratoryand/or radiographic tests (e.g., MRI, CT scans, sonograms) are necessarybefore a specific diagnosis can be made.

The pediatric endocrinology examination: Thepediatric endocrinologist will review laboratory and genetic tests to ensurethat no evidence of organ system failure or genetic disorder has been overlooked.The doctor will also evaluate the child’s growth in comparison to thatof the parents. Some questions the doctor should consider are:
 

• Does this child resemble the growth pattern of other family members?
• Is he/she a slow, average, or fast maturer, similar to his/her parents?
• Is the child’s growth potential appropriate for his/her family—i.e., isthe child expected to reach a height within the target range of his/herparents?
• How fast is the child changing and is this rate of change appropriate forage?

Finally, if the child appears to be growing abnormally without evidenceof organ system failure or dysfunction, the pediatric endocrinologist mayperform a series of blood tests to evaluate hormone function of the pituitary,particularly that of growth hormone.

CommonCauses of Short Stature

Most children with short stature will fit into one of three categories:

Familial short stature: indicatingthat short stature runs in the family.

Constitutional delay: indicatingthat height potential is normal and appropriate for the family, but therate of maturation is slow. Therefore the child will reach the final, normalheight at an older than average age.

Psychosocial dwarfism: indicatingthat psychological and social stresses in the child’s life have affectedthe child’s ability to grow normally.

Familial short stature
Familial short stature is usually the easiest to recognize. First ofall, the parents of the child will be documented to have short adult stature.The child himself will be short, but growing at a normal rate as establishedby a series of measures in the physician’s office taken every three tosix months during a one-year period of time. Usually the only study thatis required in this case is a bone age evaluation. This will show bonedevelopment that is appropriate for the child’s actual age. The expectationin familial short stature is that children will ultimately grow to a heightsimilar to that of their parents.

Constitutional delay and psychosocial dwarfism
Constitutional delay and psychosocial dwarfism are more difficult todiagnose, since in each case there is no one test that clearly identifiesthe diagnosis. In both conditions, examinations confirm delayed bone age,with all other laboratory studies being normal. Generally, in constitutionaldelay, there is a family history of late maturation, while in psychosocialdwarfism there is a history of major stress in the family (e.g., separationfrom parents, divorce, disasters, homelessness, and/or poverty).

Frequently, patients diagnosed with constitutional delay or psychosocialdwarfism undergo extensive laboratory studies to ensure that no medicalcause for growth failure has been overlooked. Patients with psychosocialdwarfism can be expected to increase their growth with a change in environment,while patients with constitutional delay are expected to reach appropriatefinal height without intervention.
 

MedicalCauses of Short Stature

Organ system failure or dysfunction of the heart, lung, kidney, or GItract are by far the most common medical cause of short stature. Theseare usually identified on the initial medical history, physical examinationand screen of laboratory data. Two well known medical causes of short stature,not readily identified in this manner, are growth hormone deficiency andTurner’s syndrome.

Growthhormone deficiency: Of the medical causes for short stature,one of the most difficult to diagnose is growth hormone deficiency. Thisis a disorder caused by inadequate production of the growth hormone, whichis made in the pituitary, a small gland lying at the base of the brain.

Children with growth hormone deficiency generally have either poor growthor low blood sugar, neither of which produces dramatic symptoms. In fact,children with growth hormone deficiency appear much like children withconstitutional delay or psychosocial dwarfism. To make the diagnosis, laboratorytests of other systems must be normal, and the patient must fail to respondto medicines known to stimulate growth hormone production and release.An MRI of the brain is usually done to ensure that a pituitary gland tumoris not causing the deficiency.

Turner’s syndrome:Ingirls with short stature, a genetic test called a karyotype(a special blood test which looks at the number, shape, and size of a person’schromosomes) should be done to determine whether their short stature isthe result of Turner’s syndrome. In Turner’s syndrome, girls are missingone of their X chromosomes.

There are a number of problems that can occur in Turner’s syndrome.In addition to having short stature, girls with Turner’s syndrome may havea variety of malformations involving the head and neck, heart, and kidneys.Since their ovaries usually do not function, these girls will fail to developduring adolescence and will be infertile. If the disorder is recognizedat a young enough age, treatment can be provided to achieve normal femalesexual development at puberty and to ensure increased height.
 

Treatmentsfor Short Stature

Appropriate treatment for short stature depends on the specific diagnosisas well as the rate of growth. If the problem is traced to a specific organsystem, treatment will focus primarily on correcting that system. For example,if a child is found to have hypothyroidism (low thyroid hormone), thenthyroid hormone replacement will be the primary treatment.  Furthertreatment, if any, will depend on the response to thyroid hormone therapy.

In the absence of a specific diagnosis, as well as in situations ofpoor growth due to genetic disorders, the decision to treat or not is frequentlybased on the child’s rate of growth—i.e., how much height has changed betweenany two visits. Therapy under these circumstances may include giving androgens(the male hormone), or growth hormone.

Growth hormonetherapy
Growth hormone therapy involves the injection of growth hormone. Thegrowth hormone used as a medication is currently derived from recombinantDNA technology — in other words, it is synthesized from genetic materialin the laboratory rather than extracted from human beings. It has beenshown that growth hormone is most effective when it is given to the childon a daily schedule rather than a more intermittent schedule. Thus, familiesmust learn the technique of giving their children daily injections of thehormone.

Side effects of growth hormone therapy:Side effects are most often related to the dose of the medication used.Too much growth hormone can result in an increase in blood glucose levelin a diabetic-like pattern. It can also cause an overgrowth of soft tissuesof the body, including the heart muscle, which can result in heart disease.

In patients with tumors of the pituitary that produce excessive growthhormone, an increase in the incidence of other tumors has caused some concernabout cancer with growth hormone therapy. Furthermore, growth hormone treatmenthas been associated with leukemia in a small group of children, most ofwho had previously been treated for leukemia and were thought to be inremission. While no study has been able to demonstrate a direct link betweengrowth hormone therapy and the development of cancer, these associationswith tumors suggests one should not use this treatment indiscriminately,and only with caution.

Androgen therapy
Androgens, the male hormones, are commonly given to pubertal male childrenwith growth failure both to increase their growth and to make them morelike their peers in terms of physical maturation. Certain androgens withlimited ability to produce male physical features are also used at lowdoses in girls to promote height growth.

Side effects of androgen therapy: Androgenscause the bones to mature rapidly and ultimately stop growing. They musttherefore be administered with care and frequent monitoring to ensure thatthe goal of increased height is attained. Furthermore, androgens are knownto have adverse effects on the liver. A range of abnormalities has beendescribed. These include a mild cholestasis (blockage of bile excretionby the liver resulting in jaundice) with minimal injury to the liver cellsthemselves that clears with withdrawal of the medication to a conditioncalled peliosis hepatis in which there are fluid filled areas throughoutthe liver that can rupture causing life threatening hemorrhage. The cholestaticinjury is most often associated with prolonged, high dose use and can beavoided by appropriate medical supervision.  On the other hand, peliosishepatis is a rare entity that may be associated with hepatic cancer aswell. Given the seriousness of these side effects, which on occasion resultin death, it is felt by some that androgens pose an unacceptable risk fora problem such as short stature, which in many cases is a cosmetic problemrather than a disorder resulting in loss of function. In any case, cautionshould be exercised in choosing androgen therapy. All children receivingit should be monitored frequently for both physical changes and changesin bone age.
 

Conclusions

Short stature can be hard to live with for many reasons. No matter whattreatment is selected, the goal of therapy is to help a child reach a finalheight appropriate for his or her family and within the acceptable rangefor adults. How successful these treatments are in achieving this goalis still unknown. They have been shown to increase an individual’s growthrate, at least initially. Final height, however, is the result of bothgrowth rate and duration of that growth rate. Thus, the length of timethat the child is treated also contributes to his/her final height.

Most studies that demonstrate benefits have evaluated only short-termtreatment. With growth hormone therapy, the effect of treatment decreaseswith time of treatment. Studies must follow children until final heightis measured to ensure that the net effect is a taller individual.

At the moment, it is not yet possible to answer this question of finalheight with absolute clarity, because recombinant growth hormone therapyhas been available only since 1985. The accumulating evidence suggeststhat final height is indeed greater in at least some groups of childrenwith short stature who are treated with growth hormone therapy.