Turner syndrome (45,X)
Definition
Turner syndrome is a chromosomal disorder affecting females, caused by complete or partial absence of one X chromosome.
The most common karyotype is 45,X (monosomy X).
Epidemiology
Incidence: 1 in 2,000–2,500 live female births.
Many conceptions are lost spontaneously during pregnancy.
Genetics
45,X accounts for approximately 50% of cases.
Other forms include:
Mosaic: 45,X/46,XX
Structural abnormalities of the X chromosome (for example, isochromosome, ring chromosome, deletions).
Pathophysiology
Streak ovaries due to accelerated oocyte loss.
Ovarian failure leads to hypergonadotropic hypogonadism.
Short stature results from SHOX gene haploinsufficiency.
Hormonal profile
Hormone | Level |
|---|---|
Estrogen | Low |
FSH | High |
LH | High |
Anti-Müllerian hormone | Low |
Clinical features
Short stature (most common feature).
Webbed neck.
Low posterior hairline.
Broad shield chest with widely spaced nipples.
Cubitus valgus.
Lymphedema of hands and feet in infancy.
Delayed puberty.
Primary amenorrhea.
Infertility.
Associated abnormalities
Cardiovascular: bicuspid aortic valve, coarctation of the aorta, aortic root dilatation.
Renal: horseshoe kidney.
Endocrine: hypothyroidism, type 2 diabetes.
Others: osteoporosis, hearing loss.
Diagnosis
Karyotyping (gold standard): 45,X.
Elevated FSH and LH, low estrogen.
Echocardiography or cardiac MRI.
Renal ultrasonography.
Management
Growth hormone therapy in childhood.
Estrogen replacement therapy to induce puberty.
Cyclic estrogen-progestin therapy after uterine development.
Screening for cardiac, renal, thyroid, hearing, and bone complications.
Fertility options: oocyte donation with assisted reproductive technology.
Complications
Infertility.
Osteoporosis.
Hypertension.
Aortic dissection.
Autoimmune thyroid disease.
Pregnancy-related cardiovascular complications.
High-yield facts
Most common female sex chromosome disorder.
Short stature and streak ovaries are characteristic.
Primary amenorrhea with elevated FSH suggests Turner syndrome.
Increased risk of coarctation of the aorta and bicuspid aortic valve.
Diagnosis is confirmed by karyotype analysis.
Academic references
Melmed S, et al. Williams Textbook of Endocrinology. 15th ed. Elsevier; 2024.
Jameson JL, et al. Harrison’s Principles of Internal Medicine. 21st ed. McGraw-Hill; 2022.
Kumar V, Abbas AK, Aster JC. Robbins & Cotran Pathologic Basis of Disease. 11th ed. Elsevier; 2020.
Gravholt CH, et al. Clinical practice guidelines for the care of girls and women with Turner syndrome. European Journal of Endocrinology. 2024;190:G53–G151.
Sybert VP, McCauley E. Turner’s syndrome. New England Journal of Medicine. 2004;351:1227–1238.
Bondy CA. Care of girls and women with Turner syndrome. Journal of Clinical Endocrinology & Metabolism. 2007;92:10–25.
McPhee SJ, Papadakis MA. Current Medical Diagnosis & Treatment 2026. McGraw-Hill; 2026.