In animals[ edit ] A clownfish — a species in which sex change from male to female is a normal process in biology Some species exhibit sequential hermaphroditism. In these species, such as many species of coral reef fishes, sex change is a normal anatomical process. A school of clownfish is always built into a hierarchy with a female fish at the top. When she dies, the most dominant male changes sex and takes her place.
Natural sex change, in both directions, has also been reported in mushroom corals. This is posited to take place in response to environmental or energetic constraints, and to improve the organism's evolutionary fitness; similar phenomena are observed in some dioecious plants. Normally, female chickens have just one functional ovary, on their left side. Although two sex organs are present during the embryonic stages of all birds, once a chicken's female hormones come into effect, it typically develops only the left ovary.
The right gonad, which has yet to be defined as an ovary, testes, or both called an ovotestis , typically remains dormant. Certain medical conditions can cause a chicken's left ovary to regress. In the absence of a functional left ovary, the dormant right sex organ may begin to grow, if the activated right gonad is an ovotestis or testes, it will begin secreting androgens. The hen does not completely change into a rooster, however. This transition is limited to making the bird phenotypically male.
This cooling will produce a chicken with a fully functioning and reproductively fertile female body-type; even though the chicken is genetically male. The overwhelming majority of natural sex changes are from a female appearance at birth to a male appearance after puberty, due to either 5-alpha-reductase deficiency 5alpha-RD-2 or beta-hydroxysteroid dehydrogenase deficiency 17beta-HSD Without these hormones, the body produces more androgens. This causes male sex characteristics to appear early or inappropriately.
As a result, the person has some or all of the physical characteristics of a female, despite having the genetic makeup of a male. The degree of sexual ambiguity varies widely in persons with incomplete AIS. Incomplete AIS can include other disorders such as Reifenstein syndrome which is associated with breast development in men.
Transsexualism and Sex reassignment surgery Humans are most commonly said to have "a sex change" when they undergo sex reassignment therapy , that is, a set of medical procedures undergone by transsexual people to alter their sexual characteristics from male to female or from female to male.
The term may also refer specifically to sex reassignment surgery , which usually refers to genital surgery only. The term is also sometimes used for the medical procedures intersex people undergo, or, more often, are subjected to as children. The term "sex change" is sometimes also used for the whole process of changing gender role "living as a woman" instead of living as a man, or vice versa , not limited to medical procedures. This process is often much more important to transgender people than the medical procedures themselves, although medically induced changes and surgeries may be needed to make a change of gender role possible, both socially and legally; they can also have a very significant impact on the person's well-being.
Many people regard the term "sex change" as factually inaccurate.