Why is menarche an indication of puberty for girls?

Answer 1

I'm not really sure what you're asking. Menarche, or a girl's first period/first menstrual cycle, can only occur during puberty, is a part of puberty, and by definition is generally considered to be one of or the LAST change the occurs in puberty for girls. Other changes such as growth spurts, changes in breast tissue that progresses to the development of breasts, hair growth in new places (e.g. underarms, pubic hair), and all the changes that are occurring in less obvious ways (changes in the brain, hormone levels, etc) all usually happen prior to or at least start before menarche (in normal, healthy girls). If you are really asking perhaps "why it is considered the culmination of puberty in girls", then the above is your answer (it happens last, or close to last). But if you did indeed mean the question exactly as written, I suppose the real answer is "It's not an indication of puberty for girls." It would simply be a definition, I suppose - menarche merely means a girl, who is currently going through puberty, has experienced another change that happens during that time. So many other changes will happen first, like I explained above, so menarche is not used as an "indication" as far as I know. It's kind of like asking "why is gaining 10 pounds an indication of increasing weight?" Menarche is simply a part of puberty, just like gaining 10 pounds is a part of increasing weight.