Short stature MCQs (FCPS/MRCPCH-style) are rarely about memorizing a long differential. They almost always resolve to four variables: growth velocity, bone age, weight, and body proportions. Get these four right and most questions fall into place.
The Four Key Discriminators
The Four Key Discriminators
1. Growth velocity — the single most important clue
- Normal velocity → favors a non-pathological cause (familial short stature, CDGP)
- Falling/crossing percentiles → pathological until proven otherwise
2. Bone age
- ≈ chronological age → familial short stature
- Delayed → CDGP, GH deficiency, hypothyroidism, chronic systemic disease
- Advanced → precocious puberty or other causes of accelerated skeletal maturation
3. Weight
- Short + underweight → chronic systemic disease / malnutrition / malabsorption
- Short + normal-to-increased weight → endocrine cause (GH deficiency, hypothyroidism)
4. Body proportions
- Proportionate → endocrine, systemic, or chromosomal cause
- Disproportionate (short limbs, abnormal upper:lower segment ratio) → skeletal dysplasia
Pattern Recognition Table
Pattern Recognition Table
| Clinical clue | Likely diagnosis |
|---|---|
| Short parents, normal velocity, bone age ≈ chronological age | Familial short stature |
| Normal birth size, delayed bone age, delayed puberty, family history of “late bloomers” | Constitutional delay of growth and puberty (CDGP) |
| Falling growth percentiles | Pathological short stature (investigate) |
| Delayed bone age + preserved/increased weight, immature facial appearance, truncal fat | GH deficiency |
| Delayed bone age + weight gain + cold intolerance/constipation/fatigue | Hypothyroidism |
| Short + recurrent diarrhea/abdominal symptoms | Celiac disease |
| Short + polyuria/polydipsia or renal findings | Chronic renal disease |
| Short + midline defects, neonatal hypoglycemia, micropenis | GH deficiency / hypopituitarism |
| Short girl + webbed neck, shield chest, widely spaced nipples | Turner syndrome |
| Short limbs, large head, frontal bossing | Achondroplasia |
| Disproportionate body habitus | Skeletal dysplasia |
Bone Age — How Much Delay Is Significant?
Bone Age — How Much Delay Is Significant?
Bone age (Greulich–Pyle or Tanner-Whitehouse) is best interpreted relative to the standard deviation for the reference population, not a fixed number of years — but for exam purposes, the following approximations are widely taught and useful:
| Bone age finding | Interpretation |
|---|---|
| Bone age ≈ chronological age | Usually normal; supports familial short stature if growth velocity is normal |
| Delayed by > 1 year | Significant delay; consider CDGP, endocrine disease, or chronic systemic disease |
| Delayed by > 2 years, especially with poor growth velocity | Marked delay; strongly suggests a pathological cause — particularly GH deficiency or hypothyroidism |
| Advanced by > 2 years | Consider precocious puberty or other causes of accelerated skeletal maturation |
Important caveat: Bone-age delay alone cannot distinguish CDGP from true endocrine disease — both show delayed bone age. The distinguishing factors are growth velocity, weight trend, pubertal status, and associated clinical features. Bone age is a supporting investigation, not a standalone diagnostic test.
Worked exam example:
“10-year-old child, chronological age 10 years, bone age 7 years” → a 3-year delay. This is a major clue pointing toward significantly delayed skeletal maturation, prompting evaluation for GH deficiency, hypothyroidism, or chronic disease (rather than simple familial short stature).
Classic Exam Distinctions
Classic Exam Distinctions
Familial short stature
Short parents + normal growth velocity + normal bone age + predicted adult height consistent with mid-parental height.
Constitutional delay of growth and puberty (CDGP)
Normal birth size + normal growth velocity + delayed bone age + delayed puberty + family history of late bloomers + eventual normal adult height.
GH deficiency
Progressive fall in height percentile + markedly delayed bone age + relatively preserved/increased weight; often immature facial appearance and increased truncal fat.
Hypothyroidism
Poor linear growth + weight gain + delayed bone age + classic hypothyroid symptoms.
The Exam Trap to Remember
Do not label a child as having an endocrine disorder simply because they are short.
A short child who is growing at a normal velocity along their own percentile most likely has familial short stature — a normal variant. The single strongest clue that points toward a pathological cause is poor/falling growth velocity, especially when paired with a delayed bone age.
