Swyer syndrome



XY gonadal dysgenesis

Also known as XY gonadal dysgenesis.

A type of hypogonadism in a person whose karyotype is 46,XY. 

They typically have normal female external genitalia, and are female.

It has been estimated that the incidence of Swyer syndrome is approximately 1 in 100,000 people.

The phenotype is female but with functionless gonads, fibrous tissue (streaked gonads) and if left untreated, will not experience puberty. 

The ovaries are typically surgically removed, as they have a significant risk of developing cancer.

Treatment relies on hormone replacement therapy.

Swyer syndrome patients are born with the appearance of a normal female in most anatomic respects except for nonfunctional gonads instead of ovaries or testes. 

Typically remains unsuspected until puberty fails to occur. 

Appear to be normal girls and are generally considered so,and 

are usually diagnosed in their teens when they fail to begin having a menstrual period.

Since gonads cannot make estrogen, breasts will not develop and the uterus will not grow and menstruate until estrogen is administered. 

As the gonads cannot make progesterone, menstrual periods will not be predictable until progestin is administered.

Gonads cannot produce eggs, so conceiving children is not possible without intervention. 

In a woman with a uterus and ovaries but without female gamete is able to become pregnant by implantation of another woman’s fertilized egg.

Streaked  gonads with Y chromosome-containing cells have a high likelihood of developing malignancy , especially gonadoblastoma.

Streak gonads are usually removed within a year or so of diagnosis, since the cancer can begin during infancy.

The first known step of sexual differentiation of a normal XY fetus is the development of testes. 

Testicular formation is initiated in the second month of gestation and requires the action of several genes, one of the earliest and most important of which is SRY.

SRY is the sex-determining region of the Y chromosome. 

SRY mutations account for many cases of Swyer syndrome.

SRY gene defects may lead to indifferent gonads faiing to differentiate into testes in an XY fetus. 

Without testes, no testosterone or antimüllerian hormone is produced. 

Without testosterone,  wolffian ducts fail to develop, and no internal male organs are formed. 

With a lack of testosterone no dihydrotestosterone is formed and consequently the external genitalia fail to virilize, resulting in normal female genitalia. 

Without anti Müllerian hormone, the Müllerian ducts develop into normal internal female organs of the uterus, fallopian tubes, cervix, vagina.

Diagnosis is prompted by the  inability of the streak gonads to produce sex hormones, so that most of the secondary sex characteristics do not develop. 

The lack of estrogenic changes such as breast development, widening of the pelvis and hips, and menstrual periods is prominent.

The adrenal glands can make limited amounts of androgens and are not affected by this syndrome, so most of these patients will develop pubic hair, though it often remains sparse.

Evaluation of delayed puberty:  elevation of gonadotropins, indicating the pituitary is providing the signal for puberty but the gonads are failing to respond, 

checking a karyotype and imaging of the pelvis. 

The karyotype reveals XY chromosomes and imaging demonstrates the presence of a uterus but no ovaries.

Treatment is with estrogen and progestogen therapy is typically promoting the development of female characteristics.

Hormone replacement therapy reduces the likelihood of osteoporosis.

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