About This Page
This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
The Bottom Line
- Karyotype 45,X (or mosaic variants) — affects ~1 in 2,500 live female births
- Key features: short stature, webbed neck, shield chest, lymphoedema in neonates, ovarian dysgenesis
- Cardiac associations: bicuspid aortic valve (most common, ~30%), coarctation of the aorta (~10%)
- Growth hormone therapy improves final adult height — start early
- Oestrogen replacement for pubertal induction and long-term bone/cardiovascular health
Overview
Turner syndrome is caused by complete or partial absence of one X chromosome in phenotypic females. The classic karyotype is 45,X (monosomy X), but approximately 50% have mosaic forms (e.g. 45,X/46,XX). It is one of the most common chromosomal abnormalities but over 99% of 45,X conceptions result in spontaneous miscarriage. The condition is characterised by short stature, gonadal dysgenesis, and a range of congenital anomalies requiring lifelong multidisciplinary management.
Epidemiology
Turner syndrome affects approximately 1 in 2,500 live female births. Most cases (>99%) are lost to spontaneous miscarriage, making it the most common chromosomal abnormality found in first-trimester miscarriages. There is no maternal age association (unlike trisomies). Diagnosis may be made antenatally (cystic hygroma on ultrasound), at birth (lymphoedema), in childhood (short stature), or at adolescence (delayed puberty/primary amenorrhoea).
Clinical Features
Symptoms
Short stature — most consistent feature; mean untreated adult height ~147 cm
Primary amenorrhoea and absent puberty (streak ovaries)
Infertility
Recurrent otitis media and conductive hearing loss
Learning difficulties (usually normal IQ but specific visuospatial and mathematical difficulties)
Signs
Webbed neck (pterygium colli)
Low posterior hairline
Shield chest with widely spaced nipples
Lymphoedema of hands and feet (especially in neonates)
Cubitus valgus (increased carrying angle)
Short 4th metacarpal
Multiple pigmented naevi
High-arched palate
Nail dysplasia
Coarctation of the aorta — radio-femoral delay, upper limb hypertension
Investigations
First-line
KaryotypeDiagnostic: 45,X (classic) or mosaic variants (45,X/46,XX etc.). Requires 30-cell analysis to detect low-level mosaicism
EchocardiogramAt diagnosis — bicuspid aortic valve (~30%), coarctation of aorta (~10%), aortic root dilatation
Second-line
Renal ultrasoundHorseshoe kidney (~10%), duplex collecting system, malrotation
FSH/LHElevated (hypergonadotropic hypogonadism) — reflects ovarian dysgenesis
Thyroid functionScreen for autoimmune hypothyroidism (Hashimoto) — association
Fasting glucose / HbA1cIncreased risk of type 2 diabetes and glucose intolerance
Specialist
Pelvic ultrasoundStreak ovaries or small/absent ovaries. Assess uterine development before considering HRT/fertility
AudiometryBaseline and regular monitoring — sensorineural and conductive hearing loss common
DEXA scanMonitor bone density — risk of osteoporosis from oestrogen deficiency
Cardiac MRIGold standard for aortic monitoring — coarctation, bicuspid aortic valve, aortic dilatation
Coeliac screen (tTG-IgA)Increased prevalence of coeliac disease in Turner syndrome
1
Growth
- Growth hormone (somatotropin) therapy — start when height falls below 2nd centile or growth velocity declines
- Continue until near-final height achieved (bone age ≥14 years, growth velocity <2 cm/year)
- Mean height gain with GH: approximately 5–8 cm above untreated adult height
- Low-dose oxandrolone may be added from age ~10 to augment growth in some cases
2
Pubertal induction and sex hormone replacement
- Oestrogen replacement from age ~11–12 years for pubertal induction (low-dose, gradually increasing)
- Add cyclical progesterone after 2 years or when breakthrough bleeding occurs → combined HRT
- Continue HRT at least until age 50 for bone, cardiovascular, and cognitive health
- Fertility: spontaneous pregnancy rare (~2–5% of mosaic patients). Egg donation with IVF is possible if uterus is adequately developed — requires cardiac assessment before pregnancy
3
Cardiovascular monitoring
- Echocardiogram at diagnosis, then every 5 years (more frequently if abnormality detected)
- Cardiac MRI in adolescence/adulthood for detailed aortic assessment
- Blood pressure monitoring at every visit — hypertension common
- Pre-pregnancy cardiac assessment is MANDATORY (risk of aortic dissection in pregnancy)
4
Annual monitoring
- Growth and pubertal assessment
- Thyroid function tests
- Fasting glucose / HbA1c
- LFTs
- Coeliac screen (if not previously done)
- Audiometry every 3–5 years
- Renal function and blood pressure
Complications
- Cardiovascular: Bicuspid aortic valve (most common cardiac defect, ~30%), coarctation of the aorta (~10%), aortic root dilatation and risk of dissection (especially in pregnancy)
- Infertility: >95% — streak ovaries with premature ovarian insufficiency
- Osteoporosis: From oestrogen deficiency — HRT is protective
- Autoimmune conditions: Hypothyroidism (Hashimoto), coeliac disease, type 1 diabetes
- Metabolic: Increased risk of type 2 diabetes, dyslipidaemia, and non-alcoholic fatty liver disease
- Hearing loss: Both conductive (childhood) and sensorineural (adult) — progressive
UKMLA Exam Tips
- 1Short female + primary amenorrhoea + webbed neck = think Turner syndrome
- 2Most common cardiac defect: bicuspid aortic valve. Most tested cardiac association: coarctation of the aorta
- 3Karyotype is 45,X (or mosaic) — NOT autosomal. No maternal age association
- 4Neonatal lymphoedema of hands/feet can be the first presentation
- 5Antenatal clue: cystic hygroma on ultrasound
- 6FSH/LH elevated = hypergonadotropic hypogonadism (ovaries are not functioning)
- 7Horseshoe kidney is the most common renal anomaly in Turner syndrome
- 8Aortic dissection risk in pregnancy — mandatory cardiac assessment before conception
practicetest your knowledge on turner syndromeApply what you've learnt with UKMLA-style questions from the iatroX Q-Bank — paediatrics and beyond.
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