Turner syndrome and gonadal dysgenesis

• Turner syndrome is the commonest chromosomal cause of short stature and delayed puberty in girls: a female with one X chromosome and a complete or partial absence of the second sex chromosome, most often 45,X. ^[1][2]
• It is not just a childhood growth problem. It is a lifelong condition: typical features include short stature, streak (non-functioning) gonads, webbed neck, broad chest, and, in roughly one-third to one-half of cases, congenital heart disease. ^[1][2]
• Growth hormone treatment is offered early, and low-dose oestrogen replacement begins around age 11 to 12 years, given transdermally when possible and titrated slowly to preserve growth. ^[1]
• Most women with Turner syndrome cannot conceive naturally, but a matured uterus can carry a pregnancy created with donor oocytes after puberty induction. ^[1]
• Gonadal dysgenesis is the broader term for any condition in which the gonads fail to develop normally. It includes Turner syndrome, complete gonadal dysgenesis with a 46,XX or 46,XY karyotype (Swyer syndrome), and mixed (mosaic) forms. ^[3]

By the end of this page you should be able to:

1. Define Turner syndrome and 45,X/46,XY mosaicism, and explain how the karyotype relates to the phenotype.
2. Recognise the typical childhood, pubertal and adult features, including the cardiac, renal and skeletal associations.
3. List the common cardiac lesions in Turner syndrome and state the screening images required.
4. Plan and dose growth hormone therapy, and explain why it is started early and monitored with IGF-I. ^[1]
5. Induce puberty with oestrogen, choose the route and dose, and time the addition of progesterone.
6. Counsel about fertility, including spontaneous puberty, fertility preservation, and pregnancy with donor oocytes.
7. Distinguish Turner syndrome from non-Turner forms of gonadal dysgenesis, including Swyer syndrome, and outline their management.

Turner syndrome is the prototype of a sex-chromosome disorder causing hypogonadism, but it is not a single karyotype. At one end sits 45,X, the classic monosomy, with the fullest phenotype. At the other sit mosaic forms and partial deletions of an X chromosome, which can produce a much milder or fragmentary picture. The unifying problem is failure of the second sex chromosome to deliver the genes needed for full ovarian and somatic development, the short-stature homeobox (SHOX) gene on the pseudoautosomal region of Xp being the best-characterised single contributor to short stature and skeletal change. ^[1][2]

The older Endocrine Society guideline of 2007 (Bondy and the Turner Syndrome Study Group, published in the Journal of Clinical Endocrinology and Metabolism) made many of these points for the first time and established oestrogen replacement as the central adult therapy. ^[4] The current international reference is the 2024 consensus guideline produced by the International Turner Syndrome Consensus Group and initiated by the European Society of Endocrinology and the Pediatric Endocrine Society, endorsed by the participating international pediatric endocrine societies and the European Society of Cardiology. ^[1] That document is written as graded recommendations (strong "recommend" and weak "suggest") and is the source of the doses and cut-offs below. ^[1]

A diagnosis of Turner syndrome is considered in an individual with a female phenotype whose karyotype contains one X chromosome with a complete or partial absence of the second sex chromosome, associated with one or more typical clinical manifestations. ^[1] The wording matters: a karyotype with 45,X alone is not enough for the diagnosis if the person has none of the features, and conversely a partial deletion with typical features does qualify. ^[1]

Karyotype patterns fall broadly into four groups. ^[1][2]

Turner syndrome is itself a form of partial gonadal dysgenesis. "Gonadal dysgenesis" as an umbrella term covers complete failure of gonadal development as well, where the external genitalia are typically female, the uterus and fallopian tubes are present, and the gonads are streaks that make no sex steroids. ^[3]

• 46,XX complete (pure) gonadal dysgenesis is best understood as the extreme end of premature ovarian failure: an XX karyotype with streak gonads and hypergonadotropic hypogonadism, sometimes familial or syndromic. ^[3]
• 46,XY complete gonadal dysgenesis, or Swyer syndrome, occurs in about 1 in 80,000 people. Affected individuals have a 46,XY karyotype but develop female external and internal genitalia, a normal or tall stature with none of the somatic features of Turner syndrome, streak gonads, elevated gonadotrophins, and a requirement for oestrogen replacement and gonadectomy because streak gonadal tissue is prone to tumour. Variants in SRY account for about 15 percent of cases and variants in MAP3K1 for up to about 18 percent. ^{[3] [1]}
• Partial (incomplete) gonadal dysgenesis produces a spectrum from ambiguous genitalia to mild under-virilisation in a 46,XY individual; these are disorders of sex development in their own right, although they share the streak-gonad problem and the tumour risk. ^[3]

Turner syndrome affects about 50 per 100,000 females in live births, which is roughly 1 in 2,000 female newborns. ^[1][2] A much higher proportion of 45,X conceptions miscarry, so the condition is considerably more common among pregnancies that do not survive to term. ^[2] Most cases are not inherited: they arise from random errors in sex-chromosome segregation in the parent's gametes or in the early embryo (X-chromosome mosaicism). ^[2]

• Karyotype. About half of individuals with Turner syndrome have true monosomy X. The rest have mosaicism or a structural abnormality of one X chromosome. ^[2]
• Cardiac and renal findings. These are present at birth, so their epidemiology is that of the underlying lesion; see below.
• Detection. Without newborn screening, many cases are diagnosed late. Clues that should prompt testing are fetal cystic hygroma or hydrops, short stature, left-sided congenital heart defects other than a bicuspid valve, unexplained delayed puberty, renal anomaly, neck webbing, dysplastic nails, and hearing loss before age 40 together with short stature. ^[1]

There is no known lifestyle or environmental risk factor, and almost all cases are sporadic. The chromosome loss is random; the only inheritance consideration is the rare familial transmission of a structurally abnormal X, and mosaic 45,X/46,XY forms in which a cryptic Y or mosaicism complicates counselling. ^[1][2]

The short stature has a defined molecular cause: loss of one copy of SHOX, which is normally present on both sex chromosomes in the pseudoautosomal region. Because SHOX escapes X-inactivation, a 45,X individual has half the normal dose, and that single change accounts for much of the growth failure and for skeletal features such as short fourth metacarpals, Madelung deformity and cubitus valgus. ^[2] Most other features do not map to a single gene; they are thought to reflect haploinsufficiency of many X-chromosomal genes that escape inactivation, with karyotype modifying severity. ^[1]

From karyotype to phenotype. A single X chromosome is enough to support life and female development, but it is not enough for two things: adequate oocyte maintenance and full stature. The gonadal story begins early in fetal life, when the primitive germ cells reach the genital ridge and then, in girls, arrest in prophase of the first meiotic division and wait for years. In Turner syndrome that wait fails: oocytes undergo accelerated apoptosis and by birth the ovary has largely been replaced by fibrous streaks. The resulting hypergonadotropic hypogonadism is the adult's problem too: no follicles remain to make oestrogen, so FSH and LH run high, puberty fails, and bones and uterus do not grow without treatment. ^[1][2]

Why pregnancy is usually impossible without help. A girl with Turner syndrome has no eggs of her own in the vast majority of cases, and her uterus is small and infantile until oestrogen is given. A small minority, concentrated among mosaic (45,X/46,XX) individuals, retain partial ovarian function into young adulthood and may conceive naturally. ^[1] Even where function is retained, it usually fails by the third decade.

Why a smaller baby matters later. The growth failure of Turner syndrome is not just pubertal. It begins before birth (mild intrauterine growth restriction), misses the childhood component of growth, loses the pubertal growth spurt, and, because SHOX is low, produces disproportion rather than just shortness: a wide chest, full neck webbing from fetal lymphoedema residues, and relatively large hands and feet. ^[1] That is why growth hormone is discussed as a childhood treatment, not an adult one.

Cardiovascular and renal vulnerability. The same developmental field that builds the gonads also patterns the left side of the heart and the kidneys: abnormal signalling during embryogenesis explains why left-sided obstructive cardiac lesions (aortic coarctation, bicuspid aortic valve, hypoplastic left heart) and horseshoe or hypoplastic kidneys cluster in 45,X. ^[1]

• Newborn to toddler: puffiness of the hands and feet from congenital lymphoedema, loose nuchal skin, a low posterior hairline, and in overtly short babies a suspicion of Turner syndrome at birth. Feeding difficulties and frequent ear infections are common.
• Childhood: short stature that becomes obvious by about age 5, often with a gap from family target height that widens each year. ^[2]
• Puberty: no breast development by age 13, primary amenorrhoea, or arrested puberty. In a girl with short stature this is the second classic presentation.
• Adults diagnosed late: primary amenorrhoea with tall-ish stature (in Swyer), or recurrent miscarriage, unexplained infertility, early menopause, hypertension, a murmur, or a family evaluation after a cardiac diagnosis. ^[1]
• Systemic: fatigue from hypothyroidism; polyuria or infections from renal anomalies; easy bruising from coagulopathy is not typical.

• Growth. Plot height repeatedly; note the fall away from the centiles. Sitting height is reduced more than standing height because of short limbs, and arm span is less than height. ^[1]
• Craniofacial. Low-set ears, epicanthic folds, a broad neck with webbing (from residual fetal lymphoedema), and a low posterior hairline. ^[1]
• Skeletal. Cubitus valgus (increased carrying angle), a short fourth metacarpal, genu valgum, and (in adolescence) Madelung deformity of the wrist. Palpate the metacarpal heads: a dimple or shortened fourth finger is a classic sign. ^[1][2]
• Thorax. Broad or "shield" chest with widely spaced nipples and a tendency to pectus.
• Cardiovascular. Listen for an ejection systolic murmur, a click of a bicuspid aortic valve, and radio-femoral delay (coarctation). Check blood pressure in all four limbs: a higher reading in the arms than the legs suggests coarctation. ^[1]
• Skin. Multiple melanocytic naevi, hypoplastic or hyperconvex nails. ^[1]
• Puberty. Assess Tanner staging; in delayed or arrested puberty, suspect hypergonadotropic hypogonadism and arrange endocrine testing.
• Hearing. Otoscopy and whispered voice; a substantial minority have progressive sensorineural hearing loss from childhood. ^[1]
• Thyroid and abdomen. Small firm thyroid, and palpation for any abdominal mass (germ-cell tumour risk in mosaics with Y material).

Turner syndrome is often suspected antenatally on a first-trimester ultrasound showing cystic hygroma, hydrops or cardiac abnormality, and may present in the newborn with lymphoedema of the hands and feet and loose neck skin. A karyotype should be available before discharge whenever it is suspected. ^[1]

The conditions that most often enter the differential are other causes of short stature and delayed puberty, and other syndromes with a webbed neck and cardiac lesions.

1. Karyotype on blood as the first-line test. A minimum of 30 metaphases must be counted. ^[1] If rapid results are needed (prenatally or in the newborn), microarray, FISH or PCR may be used first, with chromosome analysis as the confirmatory second line. ^[1]
2. When mosaicism is suspected but routine studies are normal, ask for additional metaphases (or FISH on more cells), because 45,X mosaicism may develop with age and low-level mosaicism is easily missed. ^[1]
3. Y-chromosomal material should be sought by PCR only in those with a 45,X karyotype and signs of virilisation. Searching all 45,X individuals is not endorsed. ^[1]
4. Prenatal: fetal echocardiography whenever Turner syndrome is diagnosed before birth, and confirmation by postnatal blood karyotype. ^[1] Where non-invasive prenatal testing suggests high risk, detailed ultrasound and genetic counselling come first. ^[1]

About 23 to 50 percent of individuals with Turner syndrome have congenital heart disease, most often left-sided obstructive lesions. ^[1]

Transthoracic echocardiography should be performed at diagnosis in every newly identified individual, with imaging of the aortic arch and great vessels; where the aorta cannot be fully seen or abnormality is suspected, cardiac MRI (or CT) is the most sensitive test and is advised before procedures such as pregnancy planning. ^[1] Fetal and neonatal studies consistently under-estimate coarctation, and it can only be excluded once the ductus arteriosus closes. ^[1]

Structural kidney and urinary tract malformations are found in 18 to 60 percent of individuals with Turner syndrome; horseshoe kidney and a duplicated collecting system are the most common. A renal ultrasound should be obtained at the time of diagnosis. Further laboratory testing or repeat imaging is recommended only when new renal or urinary concerns arise, such as urinary tract infection or hypertension, with annual urinalysis for proteinuria in women with renal agenesis, bilateral hypoplasia or horseshoe kidney. ^[1]

Measurements that change management:

• LH, FSH and AMH from age 8 to 9 years and yearly until 11 to 12 years, to plan puberty and fertility. ^[1]
• Thyroid function, because hypothyroidism is common in Turner syndrome. ^[1][2]
• Liver enzymes, fasting glucose (HbA1c or a glucose tolerance test), and a lipid profile, because diabetes and dyslipidaemia are increased. ^[1]
• Tissue transglutaminase and total IgA to screen for coeliac disease when there are symptoms, or at diagnosis in childhood. ^[1]
• A baseline audiogram and otoscopy. ^[1]
• Bone mineral density is not universally required in childhood, but serial DXA is used in high-risk individuals (for example after long-term oral prednisolone or delayed oestrogen). ^[1]
• Ophthalmologic examination between ages 6 months and 5 years, and scoliosis surveillance through adolescence. ^[1]

Anti-Müllerian hormone is the most useful circulating marker of remaining follicle pool. In one overview of Turner syndrome, spontaneous follicle availability was estimated at 23 to 44 percent for those with a structural X chromosome abnormality or 45,X/47,XXX mosaicism, and only 4 to 11 percent for those with a 45,X karyotype. ^[1] These are planning figures, not guarantees.

There is no staging system and no score that defines Turner syndrome beyond the diagnostic definition above and its associated features. Instead, two practical instruments are used:

• The diagnostic karyotype definition (one X chromosome with complete or partial absence of the second, with typical features), which also determines surveillance, because mosaic forms differ in cardiac and gonadal risk. ^[1]
• The Turner-specific growth charts and the cardiac imaging thresholds (for example an aortic size index above 2.0 cm per m², or an aortic height index above 20 mm per m, for defining aortic dilation) used by cardiologists and endocrinologists to trigger referral and tighter blood pressure control. ^[1]

Every patient should have a named multidisciplinary team: paediatric or adult endocrinology, cardiology (congenital if a cardiac lesion exists), nephrology where needed, audiology, ophthalmology and psychology. ^[1] Counselling early on covers the breadth of the phenotype: with modern care life expectancy is close to normal, and the majority of women with Turner syndrome complete education and employment at rates comparable to their peers, although neurocognitive support is needed for a minority. ^[1]

Blood pressure should be checked at least annually, ideally with 24-hour ambulatory monitoring, because masked hypertension is common. Hypertension is treated, with a target of under 130/80 mmHg for adults, according to the usual guidelines and with a preference for beta-blockers or angiotensin receptor blockade when aortic dilation is present. ^[1] For Turner syndrome with hypertension and a dilated aorta, treatment with a beta-blocker, an angiotensin receptor blocker, or both is the recommended drug therapy; where there is no aortic dilation, antihypertensive treatment follows the usual adult or paediatric guidelines. ^[1]

Adults with Turner syndrome benefit from a standard secondary-prevention approach to lipids and diabetes, screening and treatment of any associated hypothyroidism, coeliac disease and vitamin D deficiency, and support for bone health through regular exercise, adequate calcium and vitamin D, and early smoking avoidance. ^[1]

Growth failure in Turner syndrome is prenatal in origin and steepens through early childhood, so the opportunity to protect height is early rather than late. ^[1] Current international guidance recommends offering growth hormone treatment as young as 2 years of age when there is evidence of growth failure (a growth rate below the normal range or declining), short stature, or a high likelihood of short stature, and at any later age while the epiphyses remain open. ^[1]

Dosing: ^[1]

• Start: 45 to 50 micrograms per kilogram per day (1.3 to 1.5 mg per m² per day). ^[1]
• Up-titrate to a maximum of 68 micrograms per kilogram per day (2.0 mg per m² per day) if the response is suboptimal and adult height potential remains substantially compromised.
• Stop: continue until little growth potential remains, namely bone age 14 years or more and/or a height velocity under 2 cm per year. There is no physiological reason to continue growth hormone into the transition period once the epiphyses have closed. ^[1]

Monitoring: measure height at least every 6 months (plotted on standard female or Turner-specific growth charts) and IGF-I at least annually, generally aiming to keep IGF-I within the normal range for age, pubertal stage and sex; persistently high IGF-I is a signal to reduce the dose. ^[1] Very low-dose oestrogen pre-pubertally is not recommended routinely to boost growth, because it is not supported by the evidence and risks the pubertal clock. ^[1]

One caution in older writing that should be updated: the 2007 Endocrine Society guideline (Bondy et al.) concentrated on growth and puberty but predated the now-standard very early start; the 2024 guideline is the edition that sets out the dose and stopping rule above. ^[1][4]

Oestrogen replacement is the therapy that makes feminisation, bone mass, uterine growth and wellbeing possible. Most girls with Turner syndrome enter puberty only with treatment. ^[1][2] Natural oestrogen is begun between ages 11 and 12 when FSH is elevated on at least two sequential measurements, or earlier, at ages 9 to 10, in a girl diagnosed late with short stature already treated or late diagnosis, and is then increased slowly over 2 to 4 years to reach an adult dose. ^[1]

The current preferred preparation is transdermal 17-beta-oestradiol, which is the most physiological route; oral oestradiol is an acceptable alternative where transdermal supply is unreliable. ^[1] The 2024 guideline gives a staged dose scheme: ^[1]

Progesterone is added cyclically once breakthrough bleeding appears, or once the oestrogen dose and the uterus permit it, usually within the second to fourth year of treatment. ^[1] The standard addition is micronised progesterone 200 mg for 10 to 12 days each month, which both protects the endometrium from hyperplasia and produces predictable withdrawal bleeds. ^[1] The route and duration of progesterone should follow local practice; the key rule is that unopposed oestrogen must not continue for more than two years without a progestogen in any woman with a uterus. ^[1] In adults who have completed puberty, treatment continues as cyclic (or for some women continuous combined) oestrogen and progestogen, and oestrogen is continued as cyclic (or, for some women, continuous combined) treatment to the usual menopausal age (about 50 to 55 years) and then re-evaluated for a possible continued lower dose, because it underpins bone, cardiovascular and cognitive health as well as wellbeing. ^[1]

Oestrogen-replacement monitoring is clinical and not blood-test heavy: breast stage, growth, blood pressure, bone age, uterine ultrasound (endometrial thickness and uterine volume) and, in low-dose transdermal titration, a serum oestradiol measured about two days after patch placement. ^[1] Because patch adhesion can fail in girls with eczema and because supply of specific patches is sometimes disrupted, families should be shown how to replace a failed patch and how a single missed 24 hours of therapy can interrupt the exposure. ^[1]

Fertility counselling in Turner syndrome should be direct and early, and should happen years before it becomes urgent. ^[1]

• Spontaneous puberty and ovarian function. A minority of girls, especially those with mosaic 45,X/46,XX or a structural X abnormality, enter puberty spontaneously and maintain ovarian function into the mid-twenties. The chance of a spontaneous pregnancy in Turner syndrome overall is quoted at about 10 percent. ^[1] AMH is the best available predictor of remaining follicle pool, and FSH, LH and AMH should be measured at ages 8 to 9 and then yearly. ^[1]
• Fertility preservation. Oocyte cryopreservation is no longer regarded as experimental for young people facing gonadotoxic therapy, but in Turner syndrome it is offered only within a research or multidisciplinary framework, with careful cardiac clearance first. ^[1] Ovarian tissue cryopreservation has yielded only one recorded pregnancy in Turner syndrome so far, so it should not be presented as an established route. ^[1]
• Cardiac clearance before any fertility procedure. Controlled ovarian stimulation is cardiovascularly demanding. Pregnancy in a woman with significant aortic dilation, untreated coarctation or an unrepaired cardiac lesion carries a real risk of dissection, so complete cardiac imaging and blood pressure control are mandatory before starting, and some women are advised against pregnancy. ^[1]
• Pregnancy with donor oocytes. This is the established route. Once oestrogen has produced a mature uterus (typically by the early twenties), a pregnancy can be achieved with donor oocytes through in-vitro fertilisation, with success rates comparable to other donor-oocyte recipients of the same age. ^[1] Pregnancies in Turner syndrome carry increased risks of miscarriage, preterm birth, intrauterine growth restriction and, particularly, aortic dissection, and require cardiologist, obstetric and endocrine joint care throughout, with at least one transthoracic echocardiogram during the pregnancy and follow-up imaging afterwards. ^[1]
• Mode of delivery. Caesarean section is not automatic. Delivery planning follows the individual's cardiac state, particularly aortic dimensions. ^[1]
• Surrogacy and adoption. These should be discussed openly as legitimate paths, particularly for women advised against pregnancy, so that the consultation is not experienced as closing doors. ^[1]

• Gonadectomy. In Swyer syndrome and in any 45,X/46,XY (or other Y-bearing) form, streak gonads (or dysgenetic testes) are removed because of the well-documented risk of gonadoblastoma and dysgerminoma. The uterus is preserved if present, so that donor-oocyte pregnancy remains possible. ^[3]
• Puberty induction. As in Turner syndrome, low-dose oestrogen is begun around 11 to 12 years, with progesterone added later to protect the endometrium and to induce periods. ^[3]
• Tumour surveillance. Where gonads are retained (only when imaging and biopsy do not show tumour and the patient declines or is too young), ultrasound and tumour markers are used, but early gonadectomy is the safer default. ^[3]
• 46,XX pure gonadal dysgenesis is managed as premature ovarian failure with hormone replacement; fertility options are donor oocytes. ^[3]

The full 2024 guideline contains more than ninety recommendations. The subset that a student should be able to list without prompting: ^[1]

• Ears: hearing assessment in the newborn, then annual tympanometry to age 5 where otitis media is recurrent, and audiology surveillance thereafter, because sensorineural hearing loss accumulates. ^[1]
• Eyes: full examination between 6 months and 5 years. ^[1]
• Teeth: at least annual dental care from the first tooth eruption. ^[1]
• Bones: vitamin D sufficiency checked routinely, with bone density imaging in those at high risk. ^[1]
• Spine: examination for scoliosis at puberty and after any rapid growth. ^[1]
• Skin: annual assessment, because particular skin tumours are increased in the 45,X karyotype. ^[1]
• Sleep-disordered breathing: screened for in children, because airway and craniofacial features predispose. ^[1]
• Transition. A defined, age-appropriate transfer plan from paediatric to adult services at adolescence improves follow-up and reduces loss to care. ^[1]

Adult presentation often follows years without endocrine care. In that setting the priority order is blood pressure control and aortic imaging first, thyroid and glucose next, bone density, and only when stable an approach to fertility. Hormone replacement is not age-limited: a woman first diagnosed in her thirties still benefits from proper pubertal induction at a low starting oestrogen dose with bone-protection intent and a gradually introduced progestogen. ^[1] The 2007 Endocrine Society guideline put it succinctly: oestrogen replacement during the adult years is of critical importance for feminisation and bone health. ^[4]

• Short stature and skeletal disproportion, usually improved but not normalised by growth hormone, worsened by delayed diagnosis. ^[1]
• Delayed or absent puberty and infertility, the source of most of the long-term psychosocial burden. ^[1]
• Cardiovascular disease. Congenital lesions (bicuspid aortic valve, coarctation, partial anomalous pulmonary venous return, hypoplastic left heart) and acquired hypertension, aortic dilation and the small but real risk of aortic dissection. ^[1]
• Otologic disease. Recurrent otitis media in childhood, leading to conductive hearing loss, and progressive sensorineural loss in adults. ^[1]
• Endocrine. Autoimmune hypothyroidism, coeliac disease, glucose intolerance or type 2 (and occasionally type 1) diabetes, and primary ovarian failure. ^[1]
• Hepatic. Raised liver enzymes, common and often benign, but requiring clarification if more than twice the upper limit of normal. ^[1]
• Renal. Urinary tract infection, obstruction, or chronic kidney disease from congenital anomalies, though most are asymptomatic. ^[1]
• Skeletal. Osteopenia and osteoporosis from prolonged hypogonadism, prevented by timely oestrogen. ^[1]
• Gonadal tumours. In those with Y-chromosomal material, the streak gonad carries a risk of gonadoblastoma or dysgerminoma until it is removed. ^[1][3]
• Psychological. Attention, visuospatial and executive difficulties occur in a minority and should be screened for, not assumed. ^[1]

With modern multidisciplinary care the life expectancy of women with Turner syndrome is close to that of the general population; the excess mortality is driven mainly by cardiovascular events, particularly aortic dissection and ischaemic heart disease. ^[1] Most women live full working and family lives, helped decisively by the move from delayed, low-dose oestrogen to the earlier, more physiological replacement regimens described above. ^[1] Overall cancer risk in Turner syndrome is close to that of the general population: breast cancer risk is reduced in several series, gonadoblastoma risk is confined to women with Y-chromosomal material, and although melanoma and central nervous system tumours are reported more often than expected in some series, there is no indication for general cancer surveillance, so screening follows the standard population programmes. ^[1]

There is no population screening programme and no primary prevention for Turner syndrome. What is effective is awareness and prompt testing: a karyotype should be obtained for any girl with unexplained short stature (particularly with a gap from mid-parental height), delayed puberty, or a congenital (especially left-sided) heart lesion, and for any adult with primary amenorrhoea. ^[1][2] Prenatally, fetal echocardiography is recommended when Turner syndrome is suspected, and a postnatal blood karyotype confirms it; non-invasive prenatal testing can flag risk but is not diagnostic. ^[1] Newborn screening for Turner syndrome remains under debate because of ethical, variability and counselling issues. ^[1]

Newborns. Confirm the karyotype early, image the heart fully (and repeat echo after ductal closure), obtain a renal ultrasound, screen hearing, check blood glucose, and start growth monitoring. Counselling should be non-directive but honest about the spectrum. ^[1]

Pregnancy (existing condition being managed, or detected antenatally). Fetal counselling includes the broad phenotypic spectrum. Women with Turner syndrome who become pregnant need joint cardiology, obstetric and endocrine care, detailed aortic imaging, blood pressure control, advice on fetal aneuploidy, preterm birth and growth restriction, and planned delivery guided by cardiac state. ^[1]

Adults diagnosed after puberty. These women often have spent years without oestrogen. A staged (low-start, slow-rise) induction of puberty with hormone replacement still produces feminisation and endometrial maturation; the order of priorities is aortic imaging and blood pressure first, then thyroid, glucose and bone health, then fertility. ^[1]

The diagnosis can be made with a single standard karyotype, and many of the components of care are cheap:

• A karyotype from a regional or national laboratory is the essential and sufficient first test; repeated FISH is not needed for diagnosis. ^[1]
• A transthoracic echocardiogram rules in or out the common cardiac lesions; where even that is unavailable, blood-pressure comparison between arms and legs and careful auscultation are the minimum, with early referral.
• Growth hormone is expensive and often unavailable; where it cannot be given, the focus shifts to maximising adult height with timely, low-dose oestrogen (delayed too long, oestrogen costs height; given too early or in too high a dose, it also costs height), adequate nutrition and treatment of coeliac disease and hypothyroidism. ^[1]
• Oestrogen replacement is the component that must not be skipped: oral or transdermal preparations are increasingly affordable, and the aim is physiological replacement, not high doses.
• Renal ultrasound, annual blood pressure, thyroid function, glucose and dental care are all transferable.
• Fertility is usually achievable only where donor-oocyte in-vitro fertilisation exists; in its absence, careful HRT-focused care and honest counselling about surrogacy and adoption are the honest options. ^[1]

• Turner syndrome affects about 50 per 100,000 females (1 in 2,000 female newborns) and is usually sporadic, most often a 45,X karyotype, sometimes mosaic or structurally abnormal. ^[1][2]
• Diagnosis is made by counting at least 30 metaphases in a female with typical features and a missing or altered second sex chromosome. ^[1]
• About half of individuals have monosomy X; the karyotype predicts much of the phenotype. ^[2]
• The classic features are short stature from SHOX haploinsufficiency, streak gonads with hypergonadotropic hypogonadism, webbed neck, low posterior hairline, broad chest, cubitus valgus, short fourth metacarpal and multiple naevi. ^[1][2]
• Congenital heart disease occurs in 23 to 50 per cent of cases, principally bicuspid aortic valve (14 to 40 per cent) and aortic coarctation (4 to 15 per cent); transthoracic echo is mandatory at diagnosis, with MRI for the aorta. ^[1]
• Renal anomalies (18 to 60 per cent) include horseshoe kidney; a renal ultrasound at diagnosis is the standard screen. ^[1]
• Growth hormone starts as early as clinically justified, at 45 to 50 micrograms per kilogram per day, up to 68 micrograms per kilogram per day, continued to bone age 14 years or height velocity under 2 cm per year; monitor height and IGF-I. ^[1]
• Oestrogen begins at 11 to 12 years if FSH is elevated, transdermal 17-beta-oestradiol preferred, titrated over 2 to 4 years; micronised progesterone 200 mg for 10 to 12 days per month is added once breakthrough bleeding occurs. ^[1]
• Oestrogen replacement continues through adult life for feminisation, bone, cardiovascular and cognitive health. ^[1][4]
• Most women do not conceive naturally (overall spontaneous pregnancy rate about 10 per cent), but a donor-oocyte pregnancy is achievable once oestrogen has matured the uterus; cardiac clearance is mandatory first. ^[1]
• Swyer syndrome (46,XY complete gonadal dysgenesis) affects about 1 in 80,000 people, produces female genitalia and streak gonads without Turner stigmata, and requires gonadectomy because of tumour risk, plus oestrogen replacement. ^[3]
• The 2024 international Turner syndrome guideline superseded the earlier Endocrine Society guideline (Bondy, 2007) and provides the doses and thresholds used in this page. ^[1][4]

Plain text related subjects on MedGrasp include: primary amenorrhoea, disorders of sex development, short stature and growth hormone disorders, infertility and assisted reproduction, congenital heart disease, hypertensive disorders in pregnancy, hypogonadism, osteoporosis, and laboratory reference ranges. These are listed as plain text until verified.