Gonadal dysgenesis
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| Gonadal dysgenesis | |
|---|---|
| Specialty | Medical genetics  |
Gonadal dysgenesis is any congenital developmental disorder of the reproductive system[1] characterized by a progressive loss of germ cells on the developing gonads of an embryo.[2] This loss leads to extremely hypoplastic (underdeveloped) and dysfunctioning gonads mainly composed of fibrous tissue, hence the name streak gonads - i.e., a form of aplasia in which the ovary is replaced by functionless tissue. The accompanying hormonal failure also prevents the development of secondary sex characteristics in either sex, resulting in a sexually infantile female appearance and infertility.
The first type of gonadal dysgenesis discovered was Turner syndrome.[3]
Pathogenesis
During embryogenesis, without any external influences for or against, the human reproductive system is intrinsically conditioned to give rise to a female reproductive organisation.
As a result, if a gonad cannot express its sexual identity via its hormones—as in gonadal dysgenesis—then the affected person, no matter whether their chromosomes are XY or XX, will develop external female genitalia. Internal female genitalia, primarily the uterus, may or may not be present depending on the etiology of the disorder.
In both sexes, the commencement and progression of puberty require functional gonads that will work in harmony with the hypothalamic and pituitary glands to produce adequate hormones.
For this reason, in gonadal dysgenesis the accompanying hormonal failure also prevents the development of secondary sex characteristics in either sex, resulting in a sexually infantile female appearance and infertility.
Embryology
This condition will occur if there is an absence of both Mullerian inhibiting factor and testosterone. The absence of testosterone will result in regression of the Wolffian ducts; normal male internal reproductive tracts will not develop. The absence of Mullerian inhibiting factor will allow the Mullerian ducts to differentiate into the oviducts and uterus. In sum, this individual will possess female-like internal and external reproductive characteristics, lacking secondary sex characteristics. The genotype may be either 45,XO, 46,XX or 46,XY.
Causes
The condition may be due to:
- Turner syndrome, and its variations (i.e. mosaicism)
- XX gonadal dysgenesis, also pure gonadal dysgenesis, 46,XX
- Swyer syndrome, also pure gonadal dysgenesis, 46,XY
- Perrault syndrome, XX gonadal dysgenesis + sensorineural hearing loss
- Mixed gonadal dysgenesis
- Exposure to environmental Endocrine disruptors
See also
References
- ^ Eberhard Nieschlag; Hermann M. Behre; Susan Nieschlag (July 2009). Andrology: Male Reproductive Health and Dysfunction. Springer. pp. 221–. ISBN 978-3-540-78354-1. Retrieved 10 November 2010.
- ^ M. Sperling (2008). Pediatric endocrinology. Elsevier Health Sciences. pp. 667–. ISBN 978-1-4160-4090-3. Retrieved 27 October 2010.
- ^ Douglas T. Carrell (15 February 2010). Reproductive Endocrinology and Infertility: Integrating Modern Clinical and Laboratory Practice. Springer. p. 308. ISBN 978-1-4419-1435-4. Retrieved 27 October 2010.