Delayed or Missed Period: Causes, Evaluation, and Next Steps

Understanding Menstrual Cycle Disruptions

A period is considered delayed if >7 days past expected date; missed if no bleeding for ≥90 days (or 3 cycles) in previously regular menstruators. Pregnancy is the most common cause in reproductive-age women, but many other factors exist.

Differential Diagnosis

Category	Conditions	Mechanism
Pregnancy	Intrauterine, ectopic	hCG maintains corpus luteum → progesterone → no withdrawal bleed
Hypothalamic-Pituitary	Functional hypothalamic amenorrhea (stress, low weight, exercise), hyperprolactinemia, pituitary tumor, Sheehan syndrome	Disrupted GnRH pulsatility → low FSH/LH → anovulation
Ovarian	PCOS (most common endocrine cause), POI (premature ovarian insufficiency), ovarian cyst	Androgen excess, follicular arrest, follicle depletion
Thyroid	Hypothyroidism, hyperthyroidism	Altered SHBG, GnRH, direct ovarian effects
Adrenal	Congenital adrenal hyperplasia, Cushing syndrome	Androgen/cortisol excess
Medications	Hormonal contraceptives (OCPs, DMPA, implant, IUD), antipsychotics, antiepileptics, chemotherapy, opioids	Suppress HPO axis or cause endometrial atrophy
Systemic Illness	Uncontrolled diabetes, celiac disease, IBD, CKD, malignancy	Metabolic stress, malnutrition, inflammation
Perimenopause	Age 40–55	Declining ovarian reserve → irregular cycles

Initial Evaluation

1. Urine hCG (rule out pregnancy first).
2. History: cycle pattern, weight changes, stress, exercise, medications, galactorrhea, hirsutism, hot flashes.
3. Physical: BMI, thyroid, skin (acanthosis, hirsutism), pelvic exam.
4. Labs: TSH, prolactin, FSH/LH/estradiol (day 3 if cycling), androgens (testosterone, DHEAS, 17-OHP), glucose/HbA1c.
5. Imaging: Pelvic ultrasound (ovarian morphology, endometrial thickness).

When to See a Clinician

• 3+ months amenorrhea (or 6 months if previously irregular).
• Any bleeding after 12 months without periods (postmenopausal bleeding).
• Symptoms of androgen excess, thyroid disease, or eating disorder.
• Desire for fertility.

Cycle tracking apps and basal body temperature can provide valuable data for your provider.