Ata Acth Stim Test Interpretation

---
name: ata-acth-stim-test-interpretation
description: Performs corticotropin stimulation test to diagnose adrenal insufficiency when morning cortisol is indeterminate (3-15 µg/dL). Triggers include morning cortisol 3-15 µg/dL requiring further AI testing.
---

# Perform and interpret corticotropin stimulation test for AI diagnosis

## STEP 1 — Gather Information
Obtain morning serum cortisol level drawn between 8–9 AM after an overnight fast; confirm patient has been off glucocorticoids for at least 18–24 hours after last hydrocortisone dose or longer for synthetic glucocorticoids; assess for estrogen therapy that may increase corticosteroid-binding globulin and total cortisol.

## STEP 2 — Rule In / Rule Out
If morning cortisol ≤3 µg/dL, adrenal insufficiency is likely (rule in); if morning cortisol ≥15 µg/dL, adrenal insufficiency is unlikely (rule out); if morning cortisol is between 3–15 µg/dL, proceed to corticotropin stimulation test.

## STEP 3 — Classify or Stratify
Administer 250 µg cosyntropin (ACTH1–24) intravenously or intramuscularly; measure serum cortisol at 30 and/or 60 minutes; peak cortisol ≤18.1 µg/dL (500 nmol/L) indicates adrenal insufficiency; peak cortisol >18.1 µg/dL makes adrenal insufficiency unlikely.

## STEP 4 — Decide
If adrenal insufficiency is diagnosed, initiate glucocorticoid replacement (e.g., hydrocortisone 15–20 mg daily in divided doses) and provide stress-dose education; if adrenal insufficiency is ruled out, investigate alternative causes of symptoms.

## Clinical Guardrails / Mimics / Pitfalls
Estrogen therapy can raise total cortisol via increased corticosteroid-binding globulin, potentially masking adrenal insufficiency; ensure adequate glucocorticoid washout to avoid false-normal results; the test has moderate accuracy with limited sensitivity, so clinical judgment remains essential; peak cortisol cutoffs may vary by assay, verify local laboratory reference ranges.

## Concrete Clinical Example
A 55‑year‑old woman on oral estrogen therapy has a morning cortisol of 11 µg/dL; after confirming 24‑hour hydrocortisone washout, she undergoes standard‑dose ACTH stimulation; cortisol at 60 minutes is 16 µg/dL, leading to a diagnosis of adrenal insufficiency and initiation of hydrocortisone 10 mg morning and 5 mg afternoon.

**Source:** Hormonal Replacement in Hypopituitarism in Adults: An Endocrine Society Clinical Practice Guideline, Endocrine Society, 2016, DOI:10.1210/jc.2016-2118

> **TODO:** consider adding scripts/calc.py for the ata-acth-stim-test-interpretation calculator