Menarche is a sign of puberty and the beginning of ovarian and other endocrine functions relating to reproduction. It's an important event with the end of childhood and start of reproductive years for each woman that is preceded by a complex process of some hormonal changes in the puberty period. Moreover, it's an important clinical indicator of girls' physical, nutritional, and reproductive health. Early age at menarche, the onset of menstrual periods in girls has a substantial effect on their physical and sexual health and is related to increased risks of unfavorable health outcomes and appears to be associated with a range of emergent chronic disease risk factors. In recent decades, the age at menarche is gradually declining and decreased from 16-17 years to less than 13 years. There is evidence that childhood obesity is related to earlier menarche. This change may be partly explained by the global epidemic of obesity.