46,XX gonadal dysgenesis 46,XX gonadal dysgenesis is characteristic of
female hypogonadism with a
karyotype of 46,XX. Streak ovaries are present with non-functional tissues unable to produce the required sex steroid
oestrogen. Low levels of oestrogen effect the
HPG axis with no
feedback to the
anterior pituitary to inhibit the secretion of
FSH and
LH. If ovarian tissue is present and produces some amount of hormones, limited
menstrual cycles can occur. and
mutations in
steroidogenic acute regulatory protein (StAR protein) which regulates
steroid hormone production. In
embryogenesis, the development of the male gonads is primarily controlled by the
testis determining factor located on the sex-determining region of the Y chromosome (
SRY). If a single or combination of these genes are mutated or deleted,
downstream signalling is disrupted, leading to atypical
penis and
scrotum.
Genital Undermasculinization is the technical term for partial or complete
undifferentiated genitallia in individuals with an
SRY gene.
In utero, all fetuses are anatomically undifferentiated which are then differentiated via androgen's and SRY activation. Full undermasculinization results in a fully developed
vulva with testicles inside the body where the ovaries usually are, which is caused by conditions such as
complete androgen insensitivity syndrome. In
5α-Reductase 2 deficiency, individuals are born with normal female genitalia, however, during puberty, male differentiation and
spermatogenesis occurs. Partial genital undermasculinization can occur if the body has a
partial resistance to androgens, or if genital development is blocked, undermasculization can also be induced by certain drugs and
hormones. The overall intensity of undermasculinization can manifest itself in
hypospadias. The
surgical assignment of newborns with ambiguous genitalia to a binary sex for cosmetic purposes is considered a
human rights violation. SRY acts on gene SOX9 which drives
Sertoli cell formation and testis differentiation. An absence in SRY causes SOX9 to not be expressed at the usual time or concentration, leading to a decreased
testosterone and
anti-Müllerian hormone production. with an unknown causation for the remaining portion of 46,XY gonadal dysgenesis persons. The degree of development of the male reproductive tract is determined by the ratio of germ line cells expressing the XY genotype. giving a chromosomal count of 45, instead of the typical count of 46 chromosomes. Clinical manifestation include
primary amenorrhea,
hypergonadotropic hypogonadism, streak gonads,
infertility, and failure to develop
secondary sex characteristics. Hormones are critical for the common events in embryogenesis to occur. ==History==