What is the appropriate evaluation for amenorrhea?

Evaluation of Amenorrhea

Begin by excluding pregnancy with β-hCG testing, then obtain a comprehensive hormone panel including TSH, free T4, prolactin, LH, FSH, estradiol (E2), and AMH, while performing a thorough physical examination including external gynecologic assessment to systematically rule out organic causes before diagnosing functional hypothalamic amenorrhea. 1

Initial Assessment Framework

History Taking - Key Elements

Focus your history on these specific domains:

• Menstrual patterns: Primary amenorrhea requires evaluation by age 15 or 3 years post-breast development; secondary amenorrhea warrants workup after 3 months of absent menses (if previously regular) or 6 months (if irregular) 1, 2

• Energy balance indicators: Document exercise duration/intensity, dietary habits including restrictive eating or binge/purge behaviors, and recent weight changes. Energy availability (energy intake minus exercise expenditure) is critical—there's no single exercise threshold, as deficits can arise from either increased expenditure or decreased intake 1

• Stress assessment: Screen for psychological stressors, anxiety, depression, and life changes (college transition, grief, relationship issues). Multiple minor stressors may be more disruptive than one major stressor 1

• Medication review: Specifically ask about antipsychotics, antidepressants, contraceptives, and opioids 1

• Symptom screening: Query for thyroid dysfunction symptoms, signs of androgen excess (acne, hirsutism, hair loss), galactorrhea, headaches, visual changes, and anosmia/hyposmia (suggests Kallmann syndrome) 1

• Family history: Eating disorders, reproductive endocrine conditions, age of menarche in relatives 1

Physical Examination - Specific Findings to Document

Anthropometric measurements: Height, weight, BMI, vital signs (bradycardia suggests functional hypothalamic amenorrhea) 1

Systematic examination should identify:

• Visual fields and fundoscopy (papilledema, field defects suggesting intracranial pathology)
• Galactorrhea, thyromegaly
• Hyperandrogenism signs: acne, hirsutism, male pattern alopecia, clitoromegaly
• Hyperinsulinism markers: acanthosis nigricans, skin tags (suggests PCOS)
• Hypoestrogenism: mottled/cool extremities, hypercarotenemia
• External gynecologic exam: Assess for imperforate hymen (bluish bulge), thin/reddened vaginal mucosa (estrogen deficiency), Müllerian anomalies 1
• Bimanual exam (or pelvic ultrasound if preferred): Essential in primary amenorrhea to rule out anatomic abnormalities; helpful in secondary amenorrhea to exclude adnexal masses 1

Laboratory Evaluation Algorithm

First-Line Testing (Obtain in All Patients)

Mandatory initial panel 1:

• β-hCG (pregnancy test—always first)
• TSH and free T4
• Prolactin
• LH and FSH
• Estradiol (E2)
• AMH (anti-Müllerian hormone)

Additional Testing Based on Clinical Context

If chronic illness suspected 1:

• Complete blood count
• Comprehensive metabolic panel (electrolytes, glucose, BUN, creatinine, bicarbonate)
• Liver function tests
• ESR and/or CRP
• Hemoglobin A1C if glucose elevated

If hyperandrogenism present clinically 1:

• Total testosterone (more accurate than free testosterone in most labs)
• DHEA-S (to evaluate adrenal contribution)
• 8 AM 17-hydroxyprogesterone if late-onset congenital adrenal hyperplasia suspected

Interpreting Hormone Patterns

The pattern of hormone levels is more critical than absolute values 1. Here's how to differentiate major causes:

Functional Hypothalamic Amenorrhea

• LH: low or low-normal
• FSH: normal (often higher than LH)
• E2: <50 pg/mL (often <20 pg/mL)
• Progesterone: <1 ng/mL
• TSH/free T4: low-normal range
• Testosterone: low-normal range
• Prolactin: low-normal range 1

Primary Ovarian Insufficiency

• FSH and LH: elevated
• E2: <20 pg/mL
• Progesterone: <1 ng/mL
• Indicates absent/low ovarian reserve 1

Hyperprolactinemia

• Prolactin >100 ng/mL requires additional evaluation
• Remember: food, sleep, exercise, breast examination, and many medications can elevate prolactin 1

PCOS (may coexist with FHA)

• Elevated LH/FSH ratio
• Elevated free or total testosterone
• Elevated AMH
• Critical pitfall: Up to 50% of patients with non-hyperandrogenic PCOS phenotype (oligomenorrhea + polycystic ovaries on ultrasound) may actually have FHA 1

Organic Hypothalamic Amenorrhea

• Very low or undetectable LH and FSH
• Suggests genetic mutations affecting GnRH, pituitary/hypothalamic tumors, or infiltrative lesions 1

Imaging Considerations

When to Image

Primary amenorrhea 1:

• Pelvic ultrasound (transabdominal or transvaginal) or MRI to evaluate Müllerian tract anomalies
• Essential to exclude imperforate hymen, vaginal agenesis, uterine abnormalities

Secondary amenorrhea with concerning features:

• Brain MRI if: very low/undetectable gonadotropins, hyperprolactinemia >100 ng/mL, visual field defects, headaches, or other neurologic signs
• Pelvic imaging if: suspected Asherman syndrome (history of D&C, pelvic infection), adnexal mass on exam, or to confirm PCOS morphology

Common Diagnostic Pitfalls

1. Missing underlying PCOS in FHA patients: Women with normoandrogenic oligomenorrhea, polycystic ovarian morphology, and elevated AMH may develop hyperandrogenic PCOS when hypothalamic function normalizes. These patients are hyperresponsive to gonadotropins for fertility treatment 1

2. Misinterpreting normal LH/FSH in FHA: Clinicians expect low gonadotropins, but they're often normal in FHA—the key is the pattern (FSH > LH) combined with low estradiol 1

3. Single estradiol measurement limitations: E2 reflects a single time point; persistently low E2 (<20 pg/mL) may require GnRH stimulation testing to differentiate FHA from organic hypogonadotropic hypogonadism 1

4. Overlooking anatomic causes in primary amenorrhea: Always perform external gynecologic exam and consider imaging—don't assume functional etiology 1

5. Inadequate stress/eating disorder screening: Use validated screening tools in the patient's native language; multiple minor stressors may be more significant than obvious major stressors 1

Special Populations

Athletes: No clear exercise threshold exists for amenorrhea. Assess total energy availability, not just exercise volume. The combination of >12 hours/week exercise, low-weight sport participation, and dietary restraint carries 46% incidence of bone stress injury 1

Patients with eating disorder history: Higher risk for obstetrical complications and miscarriage; requires specific counseling 1

Adolescents: Menstrual cycles typically don't exceed 45 days even in the first postmenarchal year—persistent cycles >45 days warrant evaluation 1