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The worldwide average age of menarche is very difficult to estimate accurately, and it varies significantly by geographical region, race, ethnicity and other characteristics, and occurs mostly during a span of ages from 8 to 16, with a small percentage of girls having menarche by age 10, and the vast majority having it by the time they were 14. [3]
In response to the signals, the gonads produce hormones that stimulate libido and the growth, function, and transformation of the brain, bones, muscle, blood, skin, hair, breasts, and sex organs. Physical growth —height and weight—accelerates in the first half of puberty and is completed when an adult body has been developed.
In response to the signals, the gonads produce hormones that stimulate libido and the growth, function, and transformation of the brain, bones, muscle, blood, skin, hair, breasts, and sex organs. Physical growth—height and weight—accelerates in the first half of puberty and is completed when an adult body has been developed. Until the ...
Growth is steady though slower than in first two years. Adult height can be predicted from measurements of height at three years of age; males are approximately 53% of their adult height and females, 57%. Legs grow faster than arms. Circumference of head and chest is equal; head size is in better proportion to the body.
Growth then proceeds at a slow rate until a period of rapid growth occurs shortly before puberty (between about 9 and 15 years of age). [85] Growth is not uniform in rate and timing across all parts of the body. At birth, head size is already relatively near that of an adult, but the lower parts of the body are much smaller than adult size.
The apparent acceleration of body height occurred during the periods around the two World Wars and after the Great Depression. In the mid-nineteenth century European girls' menarche occurred at the average age of 16.5 years. One hundred years later, this age was reduced to under 12 years. [6] Increase in adult height of birth cohorts (cm/decade ...
Early puberty also puts girls at a higher risk for teasing or bullying, mental health disorders and short stature as adults. [19] [39] [56] Girls as young as 8 are increasingly starting to menstruate, develop breasts and grow pubic and underarm hair; these "biological milestones" typically occurred only at 13 or older in the past. African ...
[69] [76] As both the IGF-1R and the EGFR are independently essential for mammary gland development, and as combined application of IGF-1 and EGF, through their respective receptors, has been found to synergistically stimulate the growth of human breast epithelial cells, these growth factor systems appear to work together in mediating breast ...