Short Stature
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Direct answer
Height below the third centile (more than two standard deviations under the mean for age and sex) defines short stature, but two findings order the workup: height velocity (a prepubertal child under about 4-5 cm per year is abnormal at any centile) and the mid-parental height corridor, calculated as (father + mother + 13) ÷ 2 cm for boys and (father + mother − 13) ÷ 2 cm for girls, within about ±8.5 cm. Bone age then splits the field: familial short stature matches chronological age, constitutional delay of growth and puberty lags with a family history of late bloomers, and most pathological causes lag well behind height age. The protocol every short girl needs is a karyotype for Turner syndrome, and growth hormone deficiency is confirmed by peak GH below 10 ng/mL on two stimulation tests with low IGF-1.
What you must remember
- Definitions: short stature = height below −2 SD (third centile); pathological short stature is suggested by height velocity below the 25th centile for bone age, crossing down two centile lines, or sitting well below the mid-parental corridor.
- Mid-parental height: boys (father + mother + 13) ÷ 2, girls (father + mother − 13) ÷ 2, target range ±8.5 cm; a child inside the corridor, growing parallel to the centiles, is usually familial.
- Bone age triad: familial short stature — bone age equals chronological age; constitutional delay of growth and puberty — bone age delayed but equal to height age, with delayed puberty and often a positive family history; pathological causes — bone age markedly delayed beyond height age (hypothyroidism, growth hormone deficiency, malnutrition, coeliac disease).
- Growth hormone deficiency clues: truncal obesity, midline defects (cleft, septo-optic dysplasia), micropenis with neonatal hypoglycaemia, delayed dentition; screening with IGF-1 and IGFBP-3, confirmation by two provocation tests (clonidine, insulin tolerance, glucagon, arginine) with peak GH below 10 ng/mL (some centres 7).
- Turner rule: karyotype every undiagnosed short girl — 45,X or mosaic; look for webbed neck, shield chest, cubitus valgus, low posterior hairline, and neonatal lymphoedema.
- Proportionality check: rhizomelic limb shortening with a big head, trident hands and frontal bossing points to achondroplasia (autosomal dominant FGFR3); measure arm span and upper-to-lower segment ratio before labelling proportionate short stature.
- Everyday Indian causes to exclude first: chronic anaemia, malnutrition and chronic disease, coeliac disease (anti-tTG in short children with GI symptoms or refractory anaemia), hypothyroidism (TSH in all) and psychosocial deprivation.
- Treatment anchors: growth hormone 0.18-0.3 mg/kg/week daily subcutaneous for GHD (also Turner, chronic renal failure, SGA without catch-up, Prader-Willi); levothyroxine transforms hypothyroid short stature; testosterone for constitutional delay is a short psychosocial option, not a growth cure.
An eight-year-old girl at the third centile
She has dropped from the 25th to the third centile over three years; father 163 cm, mother 150 cm. Mid-parental height (163 + 150 − 13) ÷ 2 = 150 cm — near target, but a velocity of 3 cm/year forbids the reassurance pure familial short stature would allow. First-line tests: haemoglobin, ESR, renal and liver chemistry, TSH, anti-tTG with total IgA, left-hand bone age, and karyotype — Turner presents exactly like this, and missing it forfeits growth hormone benefit. Bone age 6.5 years with a maternal menarche at 15 brings constitutional delay in; a low-normal IGF-1 with poor velocity proceeds to paired stimulation tests. Follow-up at six months: the next two measurements, not any single report, decide variant of normal versus endocrine disease.
Where students slip
Students compute mid-parental height but forget the sex adjustment (+13 boys, −13 girls) or treat a child inside the corridor with falling velocity as familial — velocity outranks the corridor. Second: random growth hormone levels are meaningless (pulsatile secretion) — screen with IGF-1, confirm with stimulation tests. Third: any short girl without another explanation gets a Turner karyotype before growth hormone talk. Fourth: delayed bone age implies growth potential remaining; advanced bone age (early puberty, obesity) implies the opposite.
Frequently asked questions
When is short stature pathological rather than familial?
When height velocity falls below about 4-5 cm per year, centiles are crossed downward, the child sits far below the mid-parental corridor, or dysmorphism and systemic signs accompany it.
How does bone age separate the common causes?
Familial short stature keeps bone age equal to chronological age; constitutional delay delays bone age to match height age; endocrine and systemic diseases delay bone age well below height age.
How is growth hormone deficiency confirmed?
Low IGF-1 and IGFBP-3 screening followed by two stimulation tests (clonidine, insulin, glucagon or arginine), with peak growth hormone below 10 ng/mL on both defining deficiency.
Why does every short girl need a karyotype?
Turner syndrome (45,X or mosaic) is a common treatable cause whose phenotype may be subtle; diagnosis unlocks growth hormone therapy and pubertal induction planning.
What is the growth hormone dose and which non-deficiency indications exist?
0.18-0.3 mg/kg/week divided into daily subcutaneous injections, indicated additionally in Turner syndrome, chronic renal insufficiency, small-for-gestational-age children without catch-up, Prader-Willi syndrome and severe idiopathic short stature.