[Alon]

Diagnostic Approach to the Short Child

Evaluation of a child who has short stature begins with a detailed medical history that focuses on potential causes of pathologic short stature. Family history should include the heights of the parents, the age of onset of puberty for each parent, and any history of consanguinity or familial congenital anomalies. A systematic examination of all body systems includes a careful search for dysmorphic features and a calculation of the U/L ratio to exclude disproportionate shortening.

The clinician then should analyze the growth curve, paying special attention to the reliability of measurements, growth rate, and weight-to-height ratio. Each of the following scenarios requires a slightly unique approach and evaluation.

DECELERATION OF LINEAR GROWTH IN A WELL-NOURISHED OR OBESE CHILD
This is the typical growth pattern of a child who has an endocrinopathy (GHD, hypothyroidism, or glucocorticoid excess). The evaluation should begin with measurement of serum T4 and TSH concentrations, determination of bone age, and measurement of serum IGF-1 and IGFB3 concentrations. Elevated TSH and low T4 concentrations indicate primary hypothyroidism; normal thyroid function tests, a markedly delayed bone age, and low IGF-1 and IGFB3 concentrations for age in a well-nourished child are consistent with a diagnosis of GHD. The short, fat child whose results of thyroid function tests and screening tests for GHD are normal may require more extensive testing for glucocorticoid excess, including possibly an overnight dexamethasone suppression test or measurement of urinary free cortisol.

DECELERATION OF LINEAR GROWTH IN A THIN CHILD
A low weight-for-height ratio or an initial decline in weight gain followed by decreased height velocity may indicate primary gastrointestinal, nutritional, renal, or other chronic systemic disease. The history should include attention to possible silent malabsorption or evidence of inability to concentrate or acidify the urine (eg, nocturia, enuresis, or polyuria). Although many other chronic systemic illnesses may result in a similar pattern of growth failure, most are clinically obvious and do not require an extensive laboratory evaluation. When the cause of growth failure remains obscure, a complete blood count with sedimentation rate may be helpful in identifying patients who have inflammatory bowel disease, and measurement of serum electrolytes and a first void morning urinalysis should be performed (including pH and specific gravity) to identify the patient who has renal tubular acidosis or nephrogenic diabetes insipidus.

SHORT CHILD WHO HAS DYSMORPHIC FEATURES OR DISPROPORTIONATE SHORT STATURE
If dysmorphic features suggest chromosomal abnormalities or a syndrome, a karyotype should be obtained and referral made to a geneticist. If disproportionate shortening is found, a skeletal dysplasia radiologic survey (read by an experienced pediatric radiologist) will help establish the diagnosis of bone dysplasia.

DECELERATION OF LINEAR GROWTH IN ADOLESCENCE
Delayed puberty is part of the growth pattern of CDGA, and deceleration of linear growth relative to the population norm inevitably occurs as age-matched peers enter a pubertal growth spurt and the child who has CDGA does not. Children who have pathologic causes of delayed puberty (eg, Kallmann and Klinefelter syndromes) typically are not short in the prepubertal years, but may cross centiles on the linear growth curves at ages 12 to 15 years, as age-matched peers experience a pubertal growth spurt. Physical examination confirms delayed sexual maturation, and a low U/L ratio may help identify the truly hypogonadal child. The bone age is delayed in virtually all children who have delayed puberty. Elevated serum gonadotropin levels indicate primary gonadal failure; low levels are consistent with either CDGA or gonadotropin deficiency.

NORMAL HEIGHT VELOCITY IN A SHORT CHILD
This clinical scenario is most common in children who have CDGA and FSS. The child is proportionately short, otherwise healthy, and his or her linear growth is below but parallel to the lower centiles of the growth curve. A delayed bone age, a target height in the normal adult range, and a family history of delayed puberty all point to CDGA. Bone age consistent with chronologic age and a low target height suggest FSS.
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CONCLUSION
Although a number of simple diagnostic measurements (including analysis of weight relative to height and calculation of U/L ratio) and associated clinical findings (including dysmorphic features and IUGR) are helpful, the single most useful test in distinguishing the short normal child from one who has a pathologic condition is the collection of accurate height measurements over time, which allows for calculation of a height velocity. Most apparently healthy children who have short stature but are growing at a normal height velocity are normal and healthy. On the other hand, any child whose height velocity is declining, regardless of absolute height, merits careful evaluation. During the first 3 years of life, most channel changes on the linear growth curve are normal, as the large child born to small parents seeks a more "genetically appropriate" growth channel or as the child who has CDGA settles into his or her own channel at the lower centiles. Height channel changes during the teen years may be normal and indicative of variations in the onset and tempo of puberty among normal individuals. A subnormal height velocity at all other times indicates disease until proven otherwise. Indeed, the process of linear growth is a sensitive and powerful reflection of the general health of a child. The physician who understands a few simple concepts distinguishing normal from abnormal growth patterns can reassure the anxious parent of a healthy short child, embark on a focused and fiscally efficient screen for pathologic causes, and make appropriate referrals to a pediatric endocrinologist.
(Pediatrics in Review. 1998;19:92-99.)