Ages at thelarche and menarche: study in southern Thai schoolgirls.

Ages at thelarche and menarche have been studied by a status quo method in 3,029 Thai schoolgirls in Hat Yai municipality. The median ages at thelarche and menarche estimated by probit analysis are 9 years 11 months, and 12 years 5 months, respectively. Declining in ages of thelarche and menarche is observed and can be explained by improvement in nutritional status and higher living standards.