What blood work is recommended for a 14-year-old patient with concerns about growth, measuring 5 feet 3 inches in height and weighing 44 kilograms, to rule out underlying conditions affecting growth?

Blood Work for Growth Assessment in a 14-Year-Old

For a 14-year-old with height 5'3" (160 cm) and weight 44 kg, order the following initial blood work: complete blood count (CBC), comprehensive metabolic panel (CMP), thyroid function tests (TSH and free T4), celiac screening (tissue transglutaminase IgA antibodies with total IgA level), insulin-like growth factor 1 (IGF-1), and bone age X-ray. 1, 2

Growth Chart Assessment First

Before ordering labs, plot this child's measurements on CDC growth charts (recommended for children ≥24 months). 3 At 14 years old, a height of 5'3" (160 cm) and weight of 44 kg need to be evaluated against age and sex-specific percentiles to determine if they fall below the 2nd percentile threshold, which indicates potential underlying pathologic conditions requiring evaluation. 1, 2

Critical point: Growth velocity over serial measurements is more informative than a single measurement. 1, 4 If previous growth records show downward crossing of percentile lines, this indicates true growth faltering and warrants more urgent evaluation. 2

Essential Initial Laboratory Tests

Thyroid Function

• TSH and free T4 are essential because thyroid dysfunction directly affects growth velocity. 3
• Hypothyroidism is associated with reduced linear growth rate and is one of the most common endocrine causes of growth failure. 3
• Screen even if asymptomatic, as subclinical hypothyroidism can impair growth. 3

Celiac Disease Screening

• Tissue transglutaminase (tTG) IgA antibodies with total serum IgA level should be measured. 3
• Celiac disease commonly presents with poor growth as a primary symptom. 3
• If IgA deficient, use tTG IgG antibodies or deamidated gliadin peptide IgG antibodies instead. 3
• This is particularly important because celiac disease can be asymptomatic except for growth failure. 3

Complete Blood Count

• CBC screens for anemia (which can indicate chronic disease, malnutrition, or malabsorption) and other hematologic abnormalities. 1
• Identifies potential chronic inflammatory conditions affecting growth. 1

Comprehensive Metabolic Panel

• CMP evaluates kidney function, liver function, and electrolyte balance. 1
• Screens for chronic kidney disease and metabolic disorders that impair growth. 1
• Assesses nutritional status through protein markers. 1

Growth Hormone Axis

• IGF-1 (insulin-like growth factor 1) is the initial screening test for growth hormone deficiency. 5, 6
• This is a more practical initial test than direct growth hormone measurement, which requires stimulation testing. 6

Bone Age Assessment

• Left hand and wrist X-ray for bone age determines skeletal maturity and remaining growth potential. 5, 6
• Delayed bone age suggests endocrine disorders or constitutional delay; advanced bone age may indicate precocious puberty. 5

Additional Considerations Based on Clinical Context

Family Growth Patterns

Measure both parents' heights and calculate mid-parental height before interpreting results. 1, 2 If the child's height is consistent with genetic potential (both parents are short), this may represent familial short stature rather than pathology. 2

When to Add More Tests

If initial screening is normal but growth concerns persist:

• Consider karyotype (especially in females to rule out Turner syndrome) 1
• Inflammatory markers (ESR, CRP) if inflammatory bowel disease suspected 1
• Consider referral to pediatric endocrinology if height is below 2nd percentile regardless of initial lab results 2

Common Pitfalls to Avoid

Do not delay evaluation if measurements fall below the 2nd percentile, even if the child appears healthy. 2 Values below 2 standard deviations (2.3rd percentile) warrant evaluation for underlying causes including chronic malnutrition, endocrine disorders, or genetic conditions. 1

Do not assume normal growth based on a single measurement without assessing growth velocity through serial measurements plotted over time. 1, 4 A child tracking consistently at the 3rd percentile with appropriate family heights may be normal, but downward crossing of percentiles is never normal. 2

Do not order growth hormone stimulation testing as a first-line test—this should only be done by pediatric endocrinology after initial screening suggests growth hormone deficiency. 6