She started growing pubic hair at age 4. No one thought her growth curve was normal, not even her doctors. (Eight used to be the age cutoff for normal pubic-hair growth in girls; now it’s as early as 7.) For this girl, Greenspan prescribed a once-a-month shot of the hormone Leuprolide, to halt puberty’s progress.
http://www.nytimes.com/2012/04/01/magazine/puberty-before-age-10-a-new-normal.html
Benign Premature Thelarche. This condition can occur in girls as young as 18 months and is characterized by premature limited breast development without progression to a mature breast contour. Other signs of puberty do not occur, and the growth rate is prepubertal, with a bone age appropriate for chronologic age.
http://www.aafp.org/afp/1999/0701/p209.html
Normal puberty begins between eight and 14 years of age in girls and between nine and 14 years of age in boys. Pubic hair distribution is used to stage puberty, along with breast size and contour in girls and testicular volume in boys.
http://www.aafp.org/afp/1999/0701/p209.html
The age at which puberty begins varies between individuals; usually, puberty begins between 10 and 13 years of age. The age at which puberty begins is affected by both genetic factors and by environmental factors such as nutritional state and social circumstances.
https://en.wikipedia.org/wiki/Puberty
Although there is a wide range of normal ages, girls typically begin the process of puberty at age 10 or 11; boys at ages 11–12. Girls usually complete puberty by ages 15–17, while boys usually complete puberty by ages 16–17.
https://en.wikipedia.org/wiki/Puberty
Two processes contribute to the physical manifestations of puberty: adrenarche and gonadarche. Adrenarche normally occurs between six and eight years of age with increased adrenal androgen secretion; its exact biologic role is not well understood.
http://www.aafp.org/afp/1999/0701/p209.html
On average, girls begin puberty around ages 10–11; boys around ages 11–12. Girls usually complete puberty around ages 15–17, while boys usually complete puberty around ages 16–17. The major landmark of puberty for females is menarche, the onset of menstruation, which occurs on average between ages 12–13; for males, it is the first ejaculation, which occurs on average at age 13.
https://en.wikipedia.org/wiki/Puberty
Puberty is the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction.
https://en.wikipedia.org/wiki/Puberty
A diagnosis should be sought for all children with delayed sexual development, which is usually associated with short stature. In girls, delayed sexual development is defined as lack of any breast development by 14 years of age or when more than five years pass between initial growth of breast tissue and menarche.
http://www.aafp.org/afp/1999/0701/p209.html
A girl who has her first period at age 10 will stop growing younger and end up shorter than a genetically identical girl who gets her first period at age 13. That morning one of Greenspan’s patients was a 6½-year-old girl with a bone age of 9. She was the tallest girl in her class at school.
http://www.nytimes.com/2012/04/01/magazine/puberty-before-age-10-a-new-normal.html
age range for children in puberty
The age range for children in puberty is between 8 and 14 years of age in girls and between 9 and 14 years of age in boys. The range for  children in puberty is between 8 and 14 years of age in girls and between 9 and 14 years of age in boys.