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Although there is a wide range of normal ages, females typically begin the process of puberty around age 10½; males at ages 11½—12. Puberty generally ends between 15—17 for females and 16–17 for males. [1] [2] [3] Females attain reproductive maturity about four years after the first physical changes of puberty appear. [13]
Kallmann syndrome (KS) is a genetic disorder that prevents a person from starting or fully completing puberty.Kallmann syndrome is a form of a group of conditions termed hypogonadotropic hypogonadism. [1]
Puberty is considered delayed when the child has not begun puberty when two standard deviations or about 95% of children from similar backgrounds have. [7] [8] [9]In North American girls, puberty is considered delayed when breast development has not begun by age 13, when they have not started menstruating by age 15, [2] and when there is no increased growth rate. [8]
Factors other than obesity, however, perhaps genetic and/or environmental ones, are needed to explain the higher prevalence of early puberty in black versus white girls." [18] While more girls are increasingly entering puberty at younger ages, new research indicates that some boys are actually starting later (delayed puberty).
Girls have usually reached full physical development around ages 15–17, [3] [11] [34] while boys usually complete puberty around ages 16–17. [11] [34] [35] Any increase in height beyond the post-pubertal age is uncommon. Girls attain reproductive maturity about four years after the first physical changes of puberty appear. [3]
5α-reductase deficiency (5-ARD) – an autosomal recessive condition caused by a mutation of the 5-alpha reductase type 2 gene. It only affects people with Y chromosomes, namely genetic males. People with this condition are fertile, with the ability to father children, but may be raised as females due to ambiguous or feminized genitalia. [18] [19]
The human Y chromosome showing the SRY gene which codes for a protein regulating sexual differentiation. Sexual differentiation in humans is the process of development of sex differences in humans. It is defined as the development of phenotypic structures consequent to the action of hormones produced following gonadal determination. [1]
This XXY chromosome arrangement is one of the most common genetic variations from the XY karyotype, occurring in approximately one in 500 live male births. [4] [14] [37] In mammals with more than one X chromosome, the genes on all but one X chromosome are not expressed; this is known as X inactivation. This happens in XXY males, as well as ...