Endo Fha Baseline Bmd Timing

---
name: endo-fha-baseline-bmd-timing
description: This skill advises obtaining a baseline bone mineral density (BMD) measurement by dual‑energy X‑ray absorptiometry (DXA) for any adolescent or woman with six or more months of amenorrhea, and earlier when severe nutritional deficiency, other energy deficit states, or skeletal fragility are suspected. Trigger phrases include 'Get BMD after six months of amenorrhea' or 'Order DXA early due to suspected malnutrition'.
---

# Determine timing for baseline BMD measurement by DXA

## STEP 1 — Gather Information
Collect duration of amenorrhea (months), assess for history or suspicion of severe nutritional deficiency, eating disorder, excessive exercise, weight loss, prior fractures, low BMI, or other skeletal fragility; confirm patient is an adolescent or woman.

## STEP 2 — Rule In / Rule Out
If amenorrhea ≥6 months, proceed to Step 3; if amenorrhea <6 months, evaluate for high‑risk features (severe nutritional deficiency, energy deficit states, skeletal fragility).

## STEP 3 — Classify or Stratify
Classify as "baseline BMD indicated" when amenorrhea ≥6 months **or** high‑risk features are present; otherwise classify as "defer BMD".

## STEP 4 — Decide
Order a DXA scan to obtain baseline BMD (report Z‑score for adolescents/premenopausal women), document result, and repeat DXA in 1‑2 years if Z‑score ≤‑1.0 or sooner if clinical status changes.

## Clinical Guardrails / Mimics / Pitfalls
Do not delay BMD in high‑risk patients despite <6 months amenorrhea; avoid using T‑scores in premenopausal women—use age‑, sex‑, and ethnicity‑matched Z‑scores; do not diagnose osteoporosis based solely on DXA in this population per ISCD; ensure proper DXA technique and avoid repeat scans <1 year unless therapy changes; recognize that normal BMD does not exclude bone microarchitecture deficits; consider other causes of low BMD (e.g., vitamin D deficiency, glucocorticoids).

## Concrete Clinical Example
A 16‑year‑old female runner reports 8 months of amenorrhea, BMI 18 kg/m², and recent weight loss. Amenorrhea ≥6 months triggers baseline DXA; lumbar spine Z‑score is ‑1.2, prompting repeat DXA in 12 months and nutritional intervention.

**Source:** Functional Hypothalamic Amenorrhea: An Endocrine Society Clinical Practice Guideline, Endocrine Society, 2017, DOI:10.1210/jc.2017-00131