When the process of puberty starts earlier than 8 years in girls and 9 years in boys, it is called as early puberty or Precocious Puberty. The first change that occurs with puberty in girls is increase in breast size and in boys, it is increase in testicular volume. Early puberty has to be evaluated for any intracranial brain lesion which needs different therapy. If early puberty starts, it can be halted by using hormonal injections till the appropriate age.
The onset of puberty after 14 years in girls and after 15 years in boys is termed as delayed puberty. Sometimes there can be arrest of pubertal progression. Delayed puberty can be associated with a pituitary defect in hormones such as FSH and LH in which case it is called as hypogonadotrophic hypogonadism or it can be due to the defects, mutations or damage to the gonads (ovaries in females and testes in males) in which case it is called as Hypergonadotrophich hypogonadism.
In case of delayed puberty, induction of puberty needs to be done using hormones