What labs should be drawn for a female patient with primary amenorrhea?

Laboratory Evaluation for Primary Amenorrhea

For a female patient who has not had her first menses (primary amenorrhea), the mandatory initial laboratory tests are: pregnancy test, FSH, LH, prolactin, TSH, and estradiol. 1, 2, 3, 4

Initial Mandatory Laboratory Panel

The following labs should be drawn on all patients presenting with primary amenorrhea:

• Pregnancy test (urine or serum β-hCG) - Must be performed first to exclude pregnancy before interpreting other hormonal results 2, 3, 4
• FSH (follicle-stimulating hormone) - Elevated levels (>40 mIU/mL) indicate primary ovarian insufficiency; should be drawn on days 3-6 of cycle or anytime in amenorrheic patients 1, 2, 3
• LH (luteinizing hormone) - An LH/FSH ratio >2 suggests polycystic ovary syndrome (PCOS) 2, 3
• Prolactin - Elevated levels (>20 μg/L) suggest hyperprolactinemia, which may indicate pituitary adenoma or medication effect 2, 3, 4
• TSH (thyroid-stimulating hormone) - Identifies thyroid dysfunction as a reversible cause of amenorrhea 2, 3, 4
• Estradiol - Low levels suggest hypoestrogenism and help differentiate functional hypothalamic amenorrhea from other causes 1, 2

Additional Testing Based on Initial Results

If FSH is Elevated (>40 mIU/mL):

• Repeat FSH measurement - Two elevated values measured at least 4 weeks apart are required to confirm primary ovarian insufficiency 1, 2
• Karyotype (chromosomal analysis) - Mandatory in all women with non-iatrogenic primary ovarian insufficiency to identify Turner syndrome or chromosomal abnormalities 1, 3
• Fragile-X premutation testing (FMR1 gene) - Indicated in all patients with primary ovarian insufficiency, with pre-test counseling about implications 1

If Clinical Signs of Hyperandrogenism Present:

• Testosterone - Levels >2.5 nmol/L suggest PCOS or medication effect 2
• Androstenedione - Additional marker of hyperandrogenism when hirsutism or acne present 2

For Prepubertal Patients (Age ≥11 Years):

• Laboratory evaluation should be performed without regard to menstrual cycle timing since menarche has not occurred 1
• Tanner staging assessment should accompany laboratory testing to evaluate pubertal development 2

Critical Timing Considerations

• Do NOT measure FSH while patient is on hormonal contraception or hormone replacement therapy - Wait at least 2 months after discontinuation before testing 1
• Draw FSH, LH, and testosterone between days 3-6 of the menstrual cycle (or anytime in amenorrheic patients) 2
• Progesterone should be measured mid-luteal phase if assessing ovulatory status, though this is less relevant in primary amenorrhea 2

Common Pitfalls to Avoid

• Never diagnose primary ovarian insufficiency based on a single elevated FSH - Two separate measurements weeks apart are mandatory 1, 2
• Do not assume infertility in patients with primary ovarian insufficiency - Ovarian function can be unpredictable and intermittent 2, 3, 4
• Failing to perform pregnancy test first can lead to misinterpretation of all other hormonal results 2
• For prepubertal females age ≥13 years without signs of pubertal development, evaluation should be initiated even before age 15 5

Specialized Populations

Female Athletes or Patients with Low BMI:

• Evaluate for Female Athlete Triad by documenting weight changes, eating patterns, and exercise habits 2
• Consider bone mineral density testing (DXA scan) in those with energy deficiency-related amenorrhea 2

Cancer Survivors:

• FSH and estradiol levels are strongly recommended regardless of cycle timing in those treated with alkylating agents or pelvic/abdominal radiation 1
• Anti-Müllerian hormone (AMH) may provide additional information about ovarian reserve, though interpret cautiously in women under age 25 1