| Part ofa series on |
| Sex |
|---|
 |
| Biological terms |
| Sexual reproduction |
| Sexuality |
| Sexual system |
Inbiology andmedicine,feminization is the development in anorganism of physical characteristics that are usually unique to thefemales of thespecies. This may represent a normaldevelopmental process, contributing tosexual differentiation. Feminization can also be induced by environmental factors, and this phenomenon has been observed in several animal species.[1][2] In the case oftransgender hormone therapy, it is intentionally induced medically.
Inanimals, when feminization occurs in amale, or at an inappropriate developmental age, it is often due to agenetic or acquired disorder of theendocrine system. Inhumans, one of the more common manifestations of abnormal feminization isgynecomastia, the inappropriate development ofbreasts which may result from elevated levels of feminizinghormones such asestrogens.[3] Deficiency or blockage ofvirilizing hormones (androgens) can also contribute to feminization. In some cases,high levels of androgens may produce both virilizing effects (increasedbody hair, deepenedvoice, increasedmuscle mass, etc.) and feminizing effects (gynecomastia) since androgens can be converted to estrogens byaromatase in the peripheral tissues.[3]
Ininsects, feminization can occur through inheritance of reproduction-manipulatingendosymbionts. This promotes the inheritance of the endosymbionts because the endosymbionts are passed on by mothers to their eggs.[4] As such, the more endosymbiont-infected females there are in a population, the more the endosymbionts are passed on to the next generation.