Turner syndrome, also known as congenital ovarian dysgenesis, is a relatively common chromosomal aneuploidy disorder caused by the partial or complete deletion or structural abnormality of one X chromosome. Its incidence in live-born female infants is approximately 1 in 5,000 to 1 in 2,500.
Etiology and Pathogenesis
The classic Turner syndrome karyotype (45,X) accounts for about half of the cases. Mosaic Turner syndrome (45,X/46,XX) comprises around one-quarter of cases. The remaining one-quarter involves structural abnormalities of the X chromosome, such as deletions of the short or long arms, isochromosomes, or ring chromosomes.
Clinical Manifestations
The clinical presentation of Turner syndrome varies widely. Typical symptoms include short stature, gonadal dysgenesis, lymphedema, and somatic or visceral malformations. Mild cases may only exhibit slightly reduced final height and premature ovarian failure. Typical facial features include multiple nevi, ptosis, a fish-shaped mouth, and strabismus. Physical malformations may include short stature (usually less than 140 cm), a broad and webbed neck, a shield-shaped chest, low posterior hairline extending to the neck, and cubitus valgus. Secondary sexual development is often incomplete, with no breast development and an absence of pubic or axillary hair, while the external genitalia remain in an infantile female state. There may also be associated autoimmune diseases such as autoimmune thyroiditis, Graves' disease, or type 1 diabetes mellitus.
Laboratory Tests
Hormonal Measurements
Gonadal Hormones
Low levels of estradiol and progesterone are often observed, with significant elevation in gonadotropins such as FSH and LH.
Growth Hormone
There is varying degrees of growth hormone deficiency, which can be assessed using insulin-induced hypoglycemia or arginine stimulation tests to evaluate growth hormone secretion.
Chromosomal Karyotype Analysis
Chromosomal karyotype analysis provides definitive evidence for the diagnosis of the disorder.
Imaging Studies
Once Turner syndrome is diagnosed, cardiac ultrasound and other imaging studies of internal organs are used to identify potential malformations. Additional imaging techniques, such as CT or MRI, may be conducted for further clarification.
Diagnosis and Differential Diagnosis
The possibility of Turner syndrome should be considered in girls with slow growth during childhood, delayed puberty marked by primary amenorrhea, and significant congenital somatic or visceral malformations. Hormonal measurements and chromosomal karyotype analysis help confirm the diagnosis. Ultrasound findings such as cystic hygroma on the posterior neck, generalized lymphedema, pleural and peritoneal effusions, coarctation of the aorta, or left-sided cardiac malformations also suggest Turner syndrome.
Differential diagnoses include pituitary dwarfism, hypothyroidism, and constitutional delay of puberty.
Treatment
Growth Hormone Therapy
Growth hormone therapy can increase the final height of most patients by 5–10 cm. Treatment should begin during early childhood (ages 4–5) if the child's height significantly lags below the 5th percentile on the normal growth curve. The most common method of administration involves subcutaneous injections in the evening, with a dosage of 0.15 U/(kg·d). Height velocity is monitored every 4–6 months during treatment.
Sex Hormone Replacement Therapy
Nearly all patients with Turner syndrome require estrogen therapy to induce puberty, typically starting at age 15. After the completion of puberty, cyclic estrogen-progestin therapy is continued to simulate artificial menstrual cycles. Timely and appropriate estrogen replacement therapy during puberty is crucial for ensuring adequate development of the breasts and uterus. This is essential for enabling future fertility with donor eggs and for preventing complications such as osteoporosis and metabolic disorders associated with long-term estrogen deficiency.