Turner Syndrome — Symptoms, Causes & Treatment | MyMedicPlus

Turner syndrome (TS) is a chromosomal condition of females caused by the complete or partial absence or structural abnormality of one of the two X chromosomes. It is the most common sex chromosome abnormality in phenotypic females, affecting approximately 1 in 2,500 live female births worldwide — corresponding to approximately 70,000 affected females in the UK. The classic karyotype is 45,X (monosomy X — only one complete X chromosome with no second sex chromosome), which occurs in approximately 45-50% of affected individuals; the remainder have structural variants or mosaicism: 46,X,i(Xq) — isochromosome of the long arm of X (the most common structural variant — 15-20% of cases); 45,X/46,XX mosaicism (approximately 15%); 45,X/46,XY mosaicism (5-10% — requires gonadectomy due to dysgerminoma risk from the Y chromosome material); ring X chromosomes; and other partial deletions. The phenotypic severity of TS is highly variable, ranging from fetuses detected on prenatal screening with few external features, to classic Turner syndrome with all characteristic physical features, to mosaicism with only one or two features detectable. Despite this variability, three domains of concern apply universally to all karyotype variants: short stature (requiring early growth hormone treatment); gonadal dysgenesis and primary ovarian insufficiency (requiring oestrogen replacement therapy from early adolescence); and structural cardiovascular abnormalities (requiring lifelong cardiac surveillance). Turner syndrome is responsible for approximately 10% of all first-trimester miscarriages — the 45,X karyotype is the most common chromosomal abnormality in spontaneous miscarriages, and most 45,X conceptuses are lost before birth.

Turner syndrome arises from complete or partial absence of a sex chromosome: the most common mechanism is non-disjunction — failure of the sex chromosomes to properly separate during meiosis in either the egg or sperm. Unlike trisomy 21 (Down syndrome) and most trisomies, the missing X chromosome in Turner syndrome is most commonly the paternal sex chromosome — approximately 75% of 45,X cases result from loss of the paternal X chromosome (in eggs) or the Y chromosome (in sperm), suggesting the chromosomal error occurs predominantly during paternal meiosis or in the early post-fertilisation mitotic divisions rather than maternal meiosis. This is reflected in the absence of a relationship between Turner syndrome incidence and advanced maternal age — unlike Down syndrome, the prevalence of Turner syndrome is not increased in older mothers, which is important counselling information for families. The de novo nature of the chromosomal error means that in almost all cases, Turner syndrome is not inherited from parents and does not significantly increase the risk for subsequent children (recurrence risk below 1%). Mosaicism arises from post-fertilisation mitotic errors: a normal 46,XX or 46,XY zygote undergoes non-disjunction in early cell division, producing a mixed population of 45,X and 46,XX (or 46,XY) cells; the proportion of 45,X cells in different tissues determines phenotypic severity — high proportions of 45,X cells produce classic Turner syndrome features; lower proportions of 45,X cells produce milder phenotypes, sometimes with retained ovarian function and spontaneous puberty. The gene dosage explanation for Turner syndrome features centres on haploinsufficiency of genes on the X chromosome that normally escape X-inactivation (meaning both copies are required for normal expression in XX females): SHOX haploinsufficiency (short stature homeobox gene on the pseudoautosomal region) accounts for short stature and skeletal features (cubitus valgus, short fourth metacarpal, madelung deformity) — SHOX is also the gene responsible for Leri-Weill dyschondrosteosis. The cardiovascular malformations result from abnormal lymphatic development disrupting the fetal cardiovascular system through a distinct mechanism (the aortic abnormalities are related to lymphatic compression of the aortic arch during embryogenesis).

Short stature is the most universal and consistent feature, occurring in virtually all women with Turner syndrome regardless of karyotype: the average adult height without treatment is 143-147 cm (approximately 20 cm below the general female population mean), explained by haploinsufficiency of the SHOX gene; growth hormone treatment from early childhood (typically age 4-6 years) increases adult height by 5-10 cm. Gonadal dysgenesis and primary ovarian insufficiency (POI): the ovaries in 45,X Turner syndrome undergo premature regression in utero — oocytes are present but rapidly lost through accelerated apoptosis, leaving fibrous streak gonads by birth; clinically this presents as: primary amenorrhoea (failure to menstruate at all in 90% of women with classic 45,X); absent or incomplete pubertal development (failure of breast development and pubic hair growth without oestrogen replacement); infertility (the vast majority of women with TS are infertile — oocyte donation and IVF is the primary fertility option); and premature menopause even in the small minority who have spontaneous puberty (those with significant mosaicism). Cardiovascular abnormalities (the most serious feature — responsible for significantly elevated premature mortality): bicuspid aortic valve (BAV — occurring in approximately 30% of all Turner syndrome, often with aortic stenosis or regurgitation developing in adult life); coarctation of the aorta (congenital narrowing of the aorta — occurring in 10-15%); partial anomalous pulmonary venous drainage (PAPVD); and aortic root dilatation and dissection — the most feared complication, causing premature death particularly during pregnancy; aortic dissection risk is substantially elevated even in women without known BAV or coarctation. Lymphoedema: peripheral lymphoedema at birth (puffy hands and feet with thickened skin — pterygium colli and low posterior hairline result from intrauterine lymphoedema of the neck). Other classic physical features: webbed neck (pterygium colli — from intrauterine lymphoedema of the nuchum causing excess skin folds), broad shield chest with widely spaced nipples, low posterior hairline, cubitus valgus (increased carrying angle at the elbow from radial head abnormalities), short fourth and fifth metacarpals, high arched palate, and multiple melanocytic naevi. Additional organ system involvement: horseshoe kidney (renal malrotation) in 15-30% (usually asymptomatic but may predispose to UTIs and hypertension); autoimmune hypothyroidism (Hashimoto's thyroiditis) in 30% of adults; type 2 diabetes and metabolic syndrome; sensorineural hearing loss (30-60% — typically bilateral, progressive, begins in the high-frequency range from the third decade); and specific cognitive profile (generally normal intelligence with characteristic deficits in visuospatial processing and mathematics, preserved verbal intelligence and language — specific learning difficulties in approximately 50%).

Definitive diagnosis: karyotype analysis of peripheral blood lymphocytes (standard karyotype — 30 cells counted for adequate detection of mosaicism; higher cell counts required to exclude low-level mosaicism) is the gold standard and remains the diagnostic test of choice. If mosaicism with Y-chromosome material is suspected (45,X/46,XY), fluorescence in situ hybridisation (FISH) for Y-chromosome sequences may be needed as standard karyotype misses Y material in low-level mosaicism. Prenatal diagnosis: non-invasive prenatal testing (NIPT) from 10 weeks of gestation detects fetal monosomy X with high sensitivity and specificity from cell-free fetal DNA in maternal blood — positive NIPT for Turner syndrome must always be confirmed by invasive testing (amniocentesis for fetal karyotype at 15-20 weeks, or chorionic villus sampling at 11-13 weeks) as NIPT has false-positive rates and cannot detect mosaicism reliably. Turner syndrome may also be identified on antenatal ultrasound by characteristic findings: cystic hygroma of the neck (lymphatic obstruction — large fluid-filled space), fetal cardiac abnormalities (coarctation, bicuspid aortic valve), nuchal translucency above the 95th centile, hydrops fetalis, or renal abnormalities. Postnatal investigations at diagnosis: echocardiography — performed urgently at the time of diagnosis in all newly identified Turner syndrome patients to detect bicuspid aortic valve (30%), coarctation of the aorta (10-15%), and aortic root dimensions; all patients with BAV or coarctation require immediate paediatric cardiology referral. Renal ultrasound: identifies horseshoe kidney (15-30%), double collecting system, or renal agenesis — important for blood pressure monitoring and UTI risk assessment. Hormonal assessment: FSH and LH (elevated — hypergonadotrophic hypogonadism indicates ovarian failure), oestradiol (low in 45,X), inhibin B, and Anti-Mullerian hormone (AMH — very low or undetectable in complete gonadal dysgenesis; measurable in mosaics with retained follicles). Annual monitoring investigations: thyroid function tests (TSH, free T4 — 30% develop autoimmune hypothyroidism); fasting glucose and HbA1c (type 2 diabetes risk); fasting lipid profile; blood pressure (hypertension common — from renal or cardiovascular causes); audiology (hearing test — sensorineural loss from third decade); bone mineral density (DEXA scan from age 18); and ophthalmology (strabismus, amblyopia, and cataract). Cardiac MRI of the aorta every 5 years for all adults with Turner syndrome — to monitor for aortic root dilatation and detect dissection risk before surgical intervention is indicated (aortic surgery if ascending aortic diameter exceeds 4 cm or grows rapidly).

Growth hormone (recombinant GH) therapy: started from age 4-6 years, increases final adult height by 5-10 cm. Estrogen replacement therapy (ERT): initiated at 11-12 years to induce breast development, pubic hair, and uterine growth; cyclic progesterone added after 2 years for endometrial protection; continued until age 50 (natural menopause age). Oocyte donation and IVF: only realistic fertility option for most women with TS. Multidisciplinary care throughout life. Regular monitoring of treatment response, early detection of side effects, and ongoing assessment of disease progression are essential components of optimising patient outcomes over the long term. Treatment plans should be proactively reviewed and appropriately adjusted based on clinical response, patient-reported tolerability, changing patient circumstances, and continuously evolving evidence-based clinical guidelines. Meaningful shared decision-making between patients and their healthcare team, incorporating patient values and treatment preferences, consistently improves both treatment adherence and long-term outcomes.

Bicuspid aortic valve (risk of aortic dilatation and dissection — lifetime monitoring with cardiac MRI; aortic surgery if ascending aortic diameter >4 cm). Coarctation of aorta (requires surgical correction). Hypothyroidism (autoimmune — 30% by adulthood). Type 2 diabetes (insulin resistance). Osteoporosis (ovarian failure — estrogen deficiency). Sensorineural and conductive hearing loss. Visuospatial learning difficulties (specific, with normal verbal intelligence). Celiac disease (5-10%). Long-term specialist follow-up and structured regular review are essential to detect and appropriately manage complications at the earliest possible stage, minimising long-term disability, preserving organ function, and improving the overall prognosis. Patient education about the early warning signs of complications and clear guidance on when to seek urgent medical attention empowers timely help-seeking behaviour and reduces preventable serious adverse outcomes. Psychological impact — including depression, anxiety, and reduced quality of life — should be proactively assessed and addressed as part of comprehensive complication management.

Turner syndrome itself is not preventable — it arises from a random de novo chromosomal error and is not related to parental behaviour, diet, or exposure; preconception genetic counselling for affected women is appropriate but recurrence risk in subsequent pregnancies is very low (below 1%). Prevention of the preventable complications of Turner syndrome requires proactive lifelong multidisciplinary surveillance and treatment: Early growth hormone therapy (from age 4-6 years, or as soon as the diagnosis is made if the child is already short for age): starting GH treatment early maximises the treatment benefit — delaying treatment until adolescence limits the height gain possible; monitoring of IGF-1 levels and growth velocity guides dose adjustment. Oestrogen replacement therapy (ERT) initiation at 11-12 years: beginning low-dose oestrogen at the pubertal age of a healthy girl (11-12 years) is critical for both pubertal development and long-term bone and cardiovascular health; delaying ERT beyond 13-14 years causes significant bone density deficit that may not be fully correctable; low-dose transdermal oestradiol (patches) is the preferred route — more physiological than oral preparations, with less effect on IGF-1 binding protein (allowing concurrent GH treatment) and better metabolic profile; cyclic progesterone is added after 2 years to complete the endometrial protection for uterine development. Prevention of aortic dissection — the most dangerous preventable complication: all women with Turner syndrome should undergo regular cardiac MRI of the aorta every 5 years; blood pressure control is critical (target below 120/80 mmHg); avoid competitive sports and heavy exertion in women with aortic root dilatation; elective aortic surgery if the ascending aorta diameter exceeds 4 cm or the aortic size index exceeds 2.5 cm/m2; high-risk pregnancy management by a specialist multidisciplinary team including MFM (maternal-fetal medicine) and cardiology at a centre with cardiac surgery capability. Prevention of osteoporosis: ERT must be maintained until age 50 (the natural menopause age); calcium intake 1,200 mg/day and vitamin D supplementation (800-1,000 IU daily); DEXA scan from age 18 to establish baseline and monitor. Annual monitoring programme: thyroid function (TSH — Hashimoto's thyroiditis in 30%); fasting glucose/HbA1c (diabetes risk); fasting lipid profile; blood pressure; renal function (if horseshoe kidney); audiology (annual hearing tests from age 18); ophthalmology; psychological support and fertility counselling.

Seek emergency care immediately for: sudden severe chest, back, or abdominal pain in a woman with Turner syndrome — possible aortic dissection (women with TS have significantly elevated risk, especially those with bicuspid aortic valve or coarctation history); and sudden visual loss or severe headache. See a paediatric endocrinologist or clinical geneticist promptly if: a girl is significantly shorter than peers and Turner syndrome is suspected (short stature is the most universal feature — average adult height without treatment is 143-147 cm); primary amenorrhea at age 16 or absent breast development by age 14 (indicating ovarian insufficiency); and delayed puberty in a girl with any other features suggesting Turner syndrome (webbed neck, low posterior hairline, lymphedema). Women with known Turner syndrome should seek urgent cardiology review for: chest pain, shortness of breath, or hypertension — given the elevated cardiovascular risk from bicuspid aortic valve and coarctation. Attend scheduled cardiac MRI surveillance (every 5 years), annual blood pressure checks, thyroid function, and glucose monitoring — aortic dissection is a major cause of death in Turner syndrome and rigorous surveillance is life-saving. Before any planned pregnancy, Turner syndrome patients must have comprehensive cardiac evaluation including ascending aortic assessment to identify dissection risk during the haemodynamic changes of pregnancy.