# Swyer Syndrome and Gonadal Dysgenesis > NEET-PG Obstetrics and Gynaecology notes on Swyer syndrome and gonadal dysgenesis covering 46,XY streak gonads, malignancy risk and gonadectomy. - Canonical URL: https://prepelephant.com/topics/neet-pg/obstetrics-and-gynaecology/swyer-syndrome-and-gonadal-dysgenesis - Exam / course: NEET-PG · Subject: Obstetrics and Gynaecology - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-08 - Last updated: 2026-10-08 - Reference basis: Williams Gynecology; Dutta's Textbook of Gynecology - How to cite: "Swyer Syndrome and Gonadal Dysgenesis", PrepElephant, https://prepelephant.com/topics/neet-pg/obstetrics-and-gynaecology/swyer-syndrome-and-gonadal-dysgenesis ## Direct answer Swyer syndrome is pure gonadal dysgenesis in a 46,XY individual, in which streak gonads fail to produce testosterone or anti-Müllerian hormone, producing a phenotypic female with a uterus and primary amenorrhoea. Because Y-chromosome material in a dysgenetic gonad carries a substantial risk of gonadoblastoma and germ cell malignancy, the streak gonads are removed once the diagnosis is made. Oestrogen replacement then induces puberty and protects bone. ## What you must remember - **Genotype:** a 46,XY karyotype with female phenotype, most often due to an SRY gene mutation or deletion on the short arm of the Y chromosome. - **Gonads:** bilateral streak gonads without functional follicles, carrying a malignancy risk that is quoted widely, often as roughly 15 to 30 per cent where Y material is present. - **Müllerian structures:** a uterus, fallopian tubes and upper vagina are present because the absence of anti-Müllerian hormone allows the ducts to develop. - **Presentation:** primary amenorrhoea with absent breast development, infantile genitalia and often tall stature because epiphyseal fusion is delayed. - **Hormones:** raised FSH and LH with low oestradiol confirm hypergonadotropic hypogonadism, and the karyotype must be checked for mosaicism. - **Turner distinction:** Turner syndrome is 45,X with short stature and somatic features, whereas Swyer syndrome is 46,XY with a uterus and normal or tall stature. ## A stepwise diagnosis in a girl with no puberty A 16-year-old girl has female habitus, no breast development and no periods. Her ultrasound shows a small uterus and no clearly identifiable ovaries, and the karyotype returns 46,XY. The steps below set out the usual sequence from diagnosis to hormone replacement. 1. **Establish the karyotype:** Confirm 46,XY and check for mosaicism, since a mosaic pattern changes the risk estimate and the family counselling. 2. **Measure gonadotrophins:** Raised FSH and LH with low oestradiol confirm primary gonadal failure rather than a hypothalamic or pituitary cause. 3. **Look for the uterus:** Pelvic ultrasound or MRI shows a uterus, which is the key clue that separates Swyer syndrome from complete androgen insensitivity. 4. **Remove the gonads:** Bilateral gonadectomy is advised once the diagnosis is confirmed, with timing discussed at a specialist centre because of malignancy risk. 5. **Start oestrogen:** Oestrogen replacement is begun around the usual age of puberty to induce breast and uterine development and to protect bone. 6. **Add progestogen:** Once the uterus has been primed, cyclical progestogen is added to protect the endometrium, and donor-egg IVF can be considered for pregnancy. ## Where the exam tries to catch you The classic traps are confusing Swyer syndrome with Turner syndrome and leaving streak gonads in place. - **Trap:** Diagnose Swyer syndrome as Turner syndrome because of primary amenorrhoea. **Correct:** Turner syndrome is 45,X with short stature and somatic features, whereas Swyer syndrome is 46,XY with a uterus. - **Trap:** Leave the streak gonads in place to see whether they function. **Correct:** Streak gonads produce no useful hormones and carry gonadoblastoma risk, so gonadectomy is advised once the diagnosis is confirmed. - **Trap:** Assume any 46,XY girl with primary amenorrhoea has androgen insensitivity. **Correct:** Complete androgen insensitivity has normal breast development and no uterus, whereas Swyer syndrome has absent breast development and a uterus. - **Trap:** Start oestrogen alone after gonadectomy in a woman with a uterus. **Correct:** Cyclical progestogen is needed once oestrogen is given, to protect the endometrium from hyperplasia. ## Frequently asked questions ### What distinguishes Swyer syndrome from Turner syndrome? Swyer syndrome is 46,XY with a uterus and streak gonads, while Turner syndrome is 45,X with short stature and somatic features. The uterus on imaging and the karyotype together separate Swyer syndrome from Turner syndrome. ### Why are the gonads removed in Swyer syndrome? The streak gonads in Swyer syndrome have no useful function and carry a risk of gonadoblastoma and germ cell tumours, particularly where Y-chromosome material is present. Gonadectomy removes this malignancy risk, and hormone replacement then supplies the missing sex steroids. ### Why does a woman with Swyer syndrome have a uterus? A uterus develops in Swyer syndrome because the streak gonads do not secrete anti-Müllerian hormone, so the Müllerian ducts persist. This uterus is a key imaging clue that distinguishes Swyer syndrome from complete androgen insensitivity. ### What hormonal pattern supports the diagnosis of Swyer syndrome? Raised FSH and LH with low oestradiol point to primary gonadal failure in Swyer syndrome. The diagnosis is confirmed by a 46,XY karyotype, which must also be checked for mosaicism. ### When is oestrogen started in Swyer syndrome? Oestrogen replacement is started around the usual age of puberty in Swyer syndrome to induce breast development and maintain bone health. A progestogen is added later once the uterus has been primed, to protect the endometrium.