virilization virilization virilization or masculinization is the biological development of adult male characteristics in young males or females. most of the changes of virilization are produced by androgens. part of a series onsex biological terms sexual dimorphism sexual differentiation feminization virilization sex-determination system xy x0 zw z0 temperature-dependent haplodiploidy heterogametic sex homogametic sex sex chromosome x chromosome y chromosome testis-determining factor hermaphrodite sequential hermaphroditism simultaneous hermaphroditism intersex (biology) mating type sexual reproduction evolution of sexual reproduction anisogamy isogamy germ cell meiosis gametogenesis spermatogenesis oogenesis gamete spermatozoon ovum fertilization external fertilization internal fertilization sexual selection plant reproduction fungal reproduction sexual reproduction in animals sexual intercourse copulation human reproduction lordosis behavior pelvic thrust sexuality plant sexuality animal sexuality human sexuality mechanics differentiation activity sexual system dioecy gonochorism hermaphrodite virilization is most commonly used in three medical and biology of sex contexts: prenatal biological sexual differentiation, the postnatal changes of typical chromosomal male (46, xy) puberty, and excessive androgen effects in typical chromosomal females (46, xx). it is also the intended result of androgen replacement therapy in males with delayed puberty and low testosterone. prenatal virilization in the prenatal period, virilization refers to closure of the perineum, thinning and wrinkling (rugation) of the scrotum, growth of the penis, and closure of the urethral groove to the tip of the penis. in this context, masculinization is synonymous with virilization. prenatal virilization of genetic females and undervirilization of genetic males are common causes of ambiguous genitalia and intersex conditions. high prenatal virilization of a genetically female fetus can occur when an excessive amount of androgen is produced by the fetal adrenal glands or is present in maternal blood. in the severest form of congenital adrenal hyperplasia, complete masculinization of a genetically female fetus results in an apparently normal male anatomy with no palpable testes. more often, the virilization is partial and the genitalia are ambiguous. it can also be associated with progestin-induced virilisation. low undervirilization can occur if a genetic male cannot produce enough androgen or the body tissues cannot respond to it. extreme undervirilization occurs when no significant androgen hormones can be produced or the body is completely insensitive to androgens. both result in a female body. partial undervirilization produces ambiguous genitalia part-way between male and female. the mildest degree of undervirilization may be a slightly small penis. examples of undervirilization are androgen insensitivity syndrome, 5 alpha reductase deficiency, and some forms of congenital adrenal hyperplasia. normal virilization