dromlakhani Order initial screening laboratory tests
STEP 1 — Gather Information
Collect menstrual history (amenorrhea ≥3 months or cycle >45 days), assess for pregnancy symptoms, evaluate for stressors, weight loss, exercise intensity, eating disorders, and medication use. If FHA is suspected based on history, proceed to order initial screening labs.
STEP 2 — Rule In / Rule Out
Order serum b-hCG to rule out pregnancy. If positive, diagnose pregnancy and manage accordingly; if negative, continue to evaluate for systemic illness.
STEP 3 — Classify or Stratify
Review CBC, electrolytes, glucose, bicarbonate, BUN, creatinine, liver panel, and ESR/CRP for abnormalities suggestive of chronic illness. If any abnormal, classify as possible systemic illness; if all normal, classify as unlikely systemic illness.
STEP 4 — Decide
If labs suggest systemic illness, investigate underlying cause before attributing amenorrhea to FHA. If labs are normal, proceed with endocrine evaluation (TSH, free T4, prolactin, LH, FSH, estradiol, AMH).
Clinical Guardrails / Mimics / Pitfalls
Do not diagnose FHA without excluding pregnancy and systemic illness; avoid interpreting isolated lab abnormalities without clinical context; do not delay pregnancy test in sexually active patients; refrain from ordering extensive endocrine panels before basic screening labs are completed.
Concrete Clinical Example
A 19‑year‑old collegiate runner presents with 4 months of amenorrhea after increasing training and losing weight. She denies pregnancy symptoms. b‑hCG is negative; CBC, CMP, and ESR are normal. Labs are normal, so endocrine evaluation with TSH, free T4, prolactin, LH, FSH, estradiol, and AMH is pursued.
Source: Functional Hypothalamic Amenorrhea: An Endocrine Society Clinical Practice Guideline, Endocrine Society, 2017, DOI: 10.1210/jc.2017-00131