Gonadal dysgenesis
Gonadal dysgenesis is a term used to describe multiple reproductive system development disorders. They are conditions of genetic origin. It is characterized by a progressive loss of primordial germ cells on the developing gonads of an embryo.
This loss leads to extremely hypoplastic
Hypoplasia is underdevelopment or incomplete development of a tissue or organ. Although the term is not always used precisely, it properly refers to an inadequate or below-normal number of cells. Hypoplasia is similar to aplasia, but less severe. It is technically not the opposite of hyperplasia...

 (underdeveloped) and dysfunctioning gonads mainly composed of fibrous tissue, hence the name streak gonads.

It originally referred to Turner syndrome
Turner syndrome
Turner syndrome or Ullrich-Turner syndrome encompasses several conditions in human females, of which monosomy X is most common. It is a chromosomal abnormality in which all or part of one of the sex chromosomes is absent...

, but use of the term has expanded to cover other conditions.


During embryogenesis
Embryogenesis is the process by which the embryo is formed and develops, until it develops into a fetus.Embryogenesis starts with the fertilization of the ovum by sperm. The fertilized ovum is referred to as a zygote...

, 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 genetically male or female, will develop both internal and external female genitalia.

In both sexes, the commencement and progression of puberty
Puberty is the process of physical changes by which a child's body matures into an adult body capable of reproduction, as initiated by hormonal signals from the brain to the gonads; the ovaries in a girl, the testes in a boy...

 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.


This condition will occur if there is an absence of both Mullerian inhibiting factor and testosterone
Testosterone is a steroid hormone from the androgen group and is found in mammals, reptiles, birds, and other vertebrates. In mammals, testosterone is primarily secreted in the testes of males and the ovaries of females, although small amounts are also secreted by the adrenal glands...

. The absence of testosterone will result in regression
Regression (medicine)
Regression in medicine is a characteristic of diseases to show lighter symptoms without completely disappearing. At a later point, symptoms may return. These symptoms are then called recidive....

 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
The uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...

. In sum, this individual will be genotypically
The genotype is the genetic makeup of a cell, an organism, or an individual usually with reference to a specific character under consideration...

 male (i.e., XY), yet will possess female-like internal and external reproductive characteristics.


The condition may be due to:
  • Turner syndrome
    Turner syndrome
    Turner syndrome or Ullrich-Turner syndrome encompasses several conditions in human females, of which monosomy X is most common. It is a chromosomal abnormality in which all or part of one of the sex chromosomes is absent...

    , and its variations (i.e. mosaicism)
  • XX gonadal dysgenesis
    XX gonadal dysgenesis
    This syndrome is inherited as an autosomal disease. It affects both males and females but the phenotype differs. In both sexes sensorineural deafness occurs but in females ovarian dysgenesis also occurs....

    , also pure gonadal dysgenesis, 46, XX
  • Swyer syndrome
    Swyer syndrome
    Swyer syndrome, or XY gonadal dysgenesis, is a type of hypogonadism in a person whose karyotype is 46,XY. The person is externally female with streak gonads, and left untreated, will not experience puberty...

    , also pure gonadal dysgenesis, 46, XY
  • Perrault syndrome, XX gonadal dysgenesis + sensorineural hearing loss
  • Mixed gonadal dysgenesis
    Mixed gonadal dysgenesis
    Mixed gonadal dysgenesis is a condition of unusual and asymmetrical gonadal development leading to an unassigned sex differentiation. A number of differences have been reported in the karyotype, most commonly a mosaicism 45,X/ 46, XY...

  • Endocrine disruptors
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