Menarche

Menarche is the first menstrual bleeding and a late milestone of female puberty. Median age ~12–13 years (range 8–16) with secular and population variation.

Physiology

Requires sufficient endometrial proliferation under unopposed estradiol followed by withdrawal (often due to unstable immature HPO axis) leading to shedding. Early post-menarche cycles are frequently anovulatory.

Early Post-Menarche Pattern

• Irregular cycle length (typical interval 21–45 days acceptable in first 1–2 years).
• Up to ~80% anovulatory in first year, ~50% third year, ~10% by sixth year.
• Gradual maturation yields more consistent luteal progesterone production and regular intervals (24–38 days typical adult range).

Evaluation Red Flags

• No menarche by age 15 (with secondary sexual characteristics) or >3 years after thelarche.
• Primary amenorrhea (no menses) with absent secondary characteristics by 13 → evaluate for gonadal dysgenesis, hypogonadotropic hypogonadism.
• Heavy bleeding (soaking >1 pad/hour for several hours), severe anemia, or cycles <20 or >90 days persistently after 2 years.

Influencing Factors

• Nutrition and body fat (low energy availability delays; higher childhood BMI advances).
• Chronic illness, intense physical training, eating disorders, stress.
• Endocrine disorders (thyroid, hyperprolactinemia, PCOS). See polycystic_ovary_syndrome.

Health Implications

• Earlier menarche associated with increased lifetime estrogen exposure (breast cancer risk, metabolic syndrome, mood disorders).
• Later menarche may reduce bone mineral accrual window if due to hypoestrogenism.

Related Topics

• puberty
• thelarche
• pubarche
• menstrual_cycle