Puberty is a term that describes the behavioural, physiologic and anatomic changes a child experiences while the secondary sex characteristics begin to develop and the capability of sexual reproduction is attained (1) (2). In girls, menarche provides a clear sign that puberty is underway. There is no obvious counterpart of this event in boys, though one indication of a similar stage of maturity is presumably the first ejaculation, though it may be azoospermic (for some of the associated physical changes, see Wikipedia:Puberty). In adulthood, men have about 1.5 times the lean body mass of women, while women have about twice as much body fat as men. The skeletal mass of men is 1.5 times that of women
Changes also occur in gonadotropin secretion, the primary mechanisms of which are undoubtedly neural.
It is very difficult to isolate the factors that are responsible for onset of puberty, but some trends have led to some interesting conjectures. For example, the age of onset of puberty has decreased in many industrial nations over the past 100 years. This has supported some theories, which state that a critical body weight must be attained before puberty begins. However, there is some controversy over this theory.