What is the role of lab testing in the evaluation of short stature?

Updated: Jan 06, 2021
  • Author: Sunil Kumar Sinha, MD; Chief Editor: Robert P Hoffman, MD  more...
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Answer

Laboratory studies used to assess the major causes of short stature in children include the following:

  • Measurement of serum levels of insulinlike growth factor-I (IGF-I), formerly named somatomedin C, and IGF binding protein-3 (IGFBP-3)

    • These are useful tests for growth hormone deficiency (GHD), except in pubertal patients and those with history of a brain tumor.

    • Patients with certain CNS neoplasms may have normal serum growth factor levels despite having GHD, particularly during puberty.

    • Consider provocative tests of pituitary function in any patient with normal thyroid function suspected to be GH deficient.

    • Interpret a low serum IGF-I concentration cautiously because poor nutrition is associated with low serum IGF-I concentration.

    • The serum IGFBP-3 concentration has greater specificity than serum IGF-I concentration in the diagnosis of GHD.

  • Karyotype by G-banding

    • The 45,X pattern defines patients with Ullrich-Turner syndrome.

    • Because 10% of patients with Ullrich-Turner syndrome possess a mosaic karyotype (eg, 45,X; 46,XX), counting at least 30 cells reduces the possibility of failing to identify a patient with mosaic Turner syndrome (TS).

  • Measurement of serum levels of GH

    • Beyond the first months of life, endogenous GH is secreted in a pulsatile fashion. These intermittent peaks are greatest after exercise, after meals (as blood glucose levels decrease), and during deep sleep. Therefore, measuring a single random serum GH value is of no use in the evaluation of the short child. Beyond the neonatal period, values obtained during the daytime are unlikely to be detectable.

    • Although a random serum GH value of more than 10 mg/dL generally excludes GHD, a random low serum GH concentration does not confirm the diagnosis of GHD.

Other useful tests include the following:

  • CBC count for hematologic disease

  • Wintrobe sedimentation rate for inflammatory bowel disease

  • Antiendomysial immunoglobulin A (IgA) and immunoglobulin G (IgG), transglutaminase IgG, and antigliadin IgG titers for sprue (gluten enteropathy) (Antiendomysial IgA titers are more sensitive, and IgG titers are more specific.)

  • Serum total thyroxine (total T4) and thyrotropin (TSH) levels to test for hypothyroidism

    • Determination of serum free T4 concentration is necessary in patients in whom TSH deficiency, TRH deficiency, or thyroxine-binding globulin (TBG) deficiency is suspected.

    • Directly assay free T4 levels using equilibrium dialysis.

    • Many reference laboratories report a value termed the free thyroxine index, which is calculated by multiplying the total T4 by an internal standard; however, if free T4 assessment is needed, measure it directly.

  • Sweat chloride testing to exclude cystic fibrosis (CF): Consider this test in patients who are short and have a history of meconium ileus or pulmonary symptoms.

  • Serum transferrin and prealbumin concentrations for undernutrition

Murray et al estimated that through the use of genetic studies, such as copy number variant analysis, targeted gene panels, and whole-exome sequencing, a molecular diagnosis could be derived for 25-40% of children initially diagnosed with idiopathic short stature. [10]


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