What is menarche and when does it typically occur in girls?

• A. First ejaculation; ages 9-11
• B. First menstrual period; ages 12-13
• C. Onset of puberty in boys; ages 11-12
• D. Start of ovulation; ages 14-15

Answer: (B)

Menarche is the first menstrual period, a key milestone that signals the beginning of a girl’s reproductive years. It happens because the body’s puberty-related hormones surge: the brain releases GnRH, which tells the pituitary to release LH and FSH, stimulating the ovaries to produce estrogen and progesterone that drive the menstrual cycle. The first period typically occurs around ages 12–13, though it can range from about 10 to 15 years old. It’s common for cycles to be irregular for the first year or two as the body adjusts. The other options describe male sexual events or different aspects of the cycle, not the first menstrual period in girls.