[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Embryology](https://durgical.com/en/embryology/) › [Urogenital system](https://durgical.com/en/embryology/#a-urogenital) › Sex determination: SRY, anti-Müllerian hormone and testosterone

[Embryology](https://durgical.com/en/embryology/) · [Urogenital system](https://durgical.com/en/embryology/#a-urogenital)

# Sex determination: SRY, anti-Müllerian hormone and testosterone

- Process

One gene on the Y chromosome decides whether the gonad becomes a testis; three testicular hormones then shape the rest of the genital tract.

Updated 2026-11-01

**See it in 3D:** [Ovaries](https://durgical.com/en/anatomy/ovary/) · [Body of uterus](https://durgical.com/en/anatomy/body-of-uterus/) · [Ductus deferens](https://durgical.com/en/anatomy/ductus-deferens/) · [Epididymis](https://durgical.com/en/anatomy/epididymis/) · [Prostate](https://durgical.com/en/anatomy/prostate/)

## Key points

- SRY (short arm of Y) → SOX9 → Sertoli cell → testis.
- Sertoli cells secrete anti-Müllerian hormone (AMH): the Müllerian ducts regress.
- Leydig cells secrete testosterone: the Wolffian ducts survive (epididymis, ductus deferens, seminal vesicle).
- 5α-reductase type 2 turns testosterone into DHT: male external genitalia and prostate.
- Without AMH or androgens, development is female even without an ovary (as in Turner syndrome).
- Androgen receptors (AR gene, X chromosome) are needed for testosterone and DHT to act.

## What it is

Until week 7 the gonad and ducts look the same in both sexes. The SRY gene on the Y chromosome switches on SOX9 and turns the gonad into a testis; without SRY, ovarian genes such as WNT4, RSPO1 and FOXL2 take over. From then on the phenotype depends on three testicular signals: anti-Müllerian hormone, testosterone and dihydrotestosterone (DHT).

## Key facts

- Weeks 4–6: primordial germ cells migrate from the yolk sac wall to the gonadal ridges.
- Week 7: the indifferent gonad begins to become a testis if SRY is present.
- Weeks 8–10: AMH and testosterone act on the ducts.
- By about week 12 the external genitalia can be told apart; male genitalia are complete around week 14.
- The ovary expresses WNT4 and RSPO1 and represses the SOX9 pathway.

## Structure

- Chromosomal level: XX or XY.
- Gonadal level: testis or ovary, decided by SRY and SOX9 against WNT4, RSPO1 and FOXL2.
- Phenotypic level: ducts and external genitalia, decided by AMH, testosterone, DHT and their receptors.

## Step by step

- The karyotype is set at fertilization (XX or XY).
- Germ cells reach the indifferent gonad.
- With SRY, SOX9 makes Sertoli cells and a testis forms; without it, an ovary forms.
- Sertoli cells secrete AMH and the Müllerian ducts regress.
- Leydig cells secrete testosterone and the Wolffian ducts are kept.
- DHT masculinizes the external genitalia and forms the prostate.
- Without AMH or androgens, the uterus, tubes, upper vagina and female external genitalia develop.

## Markers

- SRY
- SOX9
- AMH
- WNT4
- RSPO1
- FOXL2
- DHT
- SRD5A2
- AR

## Clinical notes

- Congenital adrenal hyperplasia from 21-hydroxylase deficiency: excess adrenal androgens virilize the external genitalia of a 46,XX fetus.
- Androgen insensitivity (AR gene): 46,XY with testes, no uterus (AMH works) and female external genitalia.
- 5α-reductase deficiency: 46,XY with normal Wolffian ducts but atypical external genitalia at birth.
- Translocation of SRY onto the X chromosome: 46,XX male.
- Turner syndrome (45,X): ovaries that become fibrous streaks; Klinefelter syndrome (47,XXY): small testes.

## Memory aid

“SRY switches on, Sertoli erases, Leydig keeps, DHT shapes.” Erase Müller, keep Wolff, shape the outside.

## Test yourself

Think of the answer, then tap the question to see it.

## Which hormone makes the Müllerian ducts regress, and which cell makes it?

Anti-Müllerian hormone, made by the Sertoli cells of the fetal testis.

## Which structures depend on testosterone and which on DHT?

Testosterone keeps the Wolffian ducts (epididymis, ductus deferens, seminal vesicle); DHT forms the male external genitalia and the prostate.

## Which gene starts testis differentiation, and where is it?

SRY, on the short arm of the Y chromosome; it switches on SOX9, which makes Sertoli cells.

## Why does a 46,XY person with complete androgen insensitivity have no uterus?

Their testes make AMH normally, so the Müllerian ducts regress even though androgens cannot act.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/embryology/sex-determination-sry-anti-mullerian-hormone-and-testosterone/)

## See it in 3D

The structures of Durgical's 3D anatomy where it is found.

- [Ovaries](https://durgical.com/en/anatomy/ovary/)
- [Body of uterus](https://durgical.com/en/anatomy/body-of-uterus/)
- [Ductus deferens](https://durgical.com/en/anatomy/ductus-deferens/)
- [Epididymis](https://durgical.com/en/anatomy/epididymis/)
- [Prostate](https://durgical.com/en/anatomy/prostate/)

## Related

- [Gonads and the descent of the testis](https://durgical.com/en/embryology/gonads-and-the-descent-of-the-testis/)
- [Genital ducts: Wolffian (mesonephric) and Müllerian (paramesonephric)](https://durgical.com/en/embryology/genital-ducts-wolffian-and-mullerian/)
- [External genitalia and their male–female homologues](https://durgical.com/en/embryology/external-genitalia-and-their-male-female-homologues/)
- [Differences of sex development: CAH, AIS and 5α-reductase](https://durgical.com/en/embryology/differences-of-sex-development-cah-ais-and-5-reductase/)
- [Gametogenesis: spermatogenesis and oogenesis](https://durgical.com/en/embryology/gametogenesis-spermatogenesis-and-oogenesis/)
- [Meiosis and nondisjunction: where trisomies come from](https://durgical.com/en/embryology/meiosis-and-nondisjunction-where-trisomies-come-from/)
- [Adrenal gland: cortex from mesoderm, medulla from neural crest](https://durgical.com/en/embryology/adrenal-gland-cortex-from-mesoderm-medulla-from-neural-crest/)
- [Androgens, diethylstilbestrol and other hormones](https://durgical.com/en/embryology/androgens-diethylstilbestrol-and-other-hormones/)

## Related conditions

- [Congenital adrenal hyperplasia due to 21-hydroxylase deficiency](https://durgical.com/en/conditions/congenital-adrenal-hyperplasia-due-to-21-hydroxylase-deficiency/)
- [Turner syndrome](https://durgical.com/en/conditions/turner-syndrome/)
- [Klinefelter syndrome (47,XXY)](https://durgical.com/en/conditions/klinefelter-syndrome/)

[← All of embryology](https://durgical.com/en/embryology/)

Educational content on embryonic development; not a guide to prenatal diagnosis or to medicines in pregnancy and no substitute for a health professional's advice. No doses are given.

Sources: [Embryology, Sexual Development - StatPearls - NCBI Bookshelf](https://www.ncbi.nlm.nih.gov/books/NBK557601/) (StatPearls Publishing (NCBI Bookshelf), 2023); [Embryology, Genitourinary - StatPearls - NCBI Bookshelf](https://www.ncbi.nlm.nih.gov/books/NBK559309/) (StatPearls Publishing (NCBI Bookshelf), 2023).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/embryology/sex-determination-sry-anti-mullerian-hormone-and-testosterone/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/embryology/sex-determination-sry-anti-mullerian-hormone-and-testosterone/