Missed Period: 10 Common Causes & When to See a Doctor

Top Causes of Amenorrhea / Oligomenorrhea

1. Pregnancy – Most common; test first.
2. Hormonal contraception – Pill, patch, ring, shot, IUD (especially hormonal) → withdrawal bleed may be absent/light.
3. PCOS – Androgen excess, anovulation; irregular cycles, hirsutism, acne.
4. Thyroid dysfunction – Hypo‑ or hyperthyroidism disrupts HPO axis.
5. Chronic stress – HPA axis suppresses GnRH → hypothalamic amenorrhea.
6. Excessive exercise / low energy availability – Female athlete triad / RED‑S.
7. Weight loss / eating disorders – Low leptin → GnRH suppression.
8. Premature ovarian insufficiency (POI) – <40 yrs; elevated FSH.
9. Hyperprolactinemia – Prolactinoma, meds (antipsychotics, metoclopramide).
10. Chronic illness / medications – CKD, chemo, opioids, GLP‑1 agonists.

When to Seek Evaluation

• Missed ≥3 cycles (or 6 months if previously irregular).
• Pregnancy test positive.
• Associated symptoms (hot flashes, galactorrhea, hirsutism, pelvic pain, weight change).
• Age <16 with no menarche (primary amenorrhea).

Workup

hCG, TSH, prolactin, FSH/LH, estradiol, androgen panel ± pelvic ultrasound ± MRI if prolactin high or CNS signs.