dromlakhani Screen central hypothyroidism patients for adrenal insufficiency before levothyroxine
STEP 1 — Gather Information
Confirm CH diagnosis: low or low‑normal free T4 (fT4) with non‑elevated TSH in the setting of pituitary disease; assess hypothyroid symptoms; obtain baseline morning serum cortisol (8‑9 AM) if feasible.
STEP 2 — Rule In / Rule Out
Determine if AI testing is feasible (morning cortisol or ACTH stimulation test can be performed). If not feasible, proceed to empiric glucocorticoid therapy; if feasible, move to biochemical evaluation.
STEP 3 — Classify or Stratify
Interpret morning cortisol: <3 µg/dL suggests AI; >15 µg/dL makes AI unlikely; values 3‑15 µg/dL require low‑dose (1 µg) or standard‑dose (250 µg) ACTH stimulation test, with peak cortisol <18.1 µg/dL indicating AI.
STEP 4 — Decide
If AI is confirmed, initiate glucocorticoid replacement (e.g., hydrocortisone 15‑20 mg daily in divided doses) before starting L‑T4; if AI is ruled out, begin L‑T4 therapy targeting mid‑to‑upper reference range fT4; if testing was not feasible, prescribe empiric glucocorticoid therapy (same dosing) while arranging definitive AI evaluation.
Clinical Guardrails / Mimics / Pitfalls
Do not start L‑T4 without assessing AI due to risk of precipitating adrenal crisis; avoid random cortisol for diagnosis; do not use fludrocortisone in secondary AI; ensure patients receive stress‑dose education and emergency glucocorticoid kit; remember that estrogen can raise total cortisol via CBG, potentially masking AI.
Concrete Clinical Example
A 50‑year‑old man with non‑functioning pituitary adenoma post‑resection presents with low fT4 and normal TSH; morning cortisol is 2.5 µg/dL (<3 µg/dL), confirming AI; he receives hydrocortisone 10 mg on waking and 5 mg in the afternoon before L‑T4 is started.
Source: Hormonal Replacement in Hypopituitarism in Adults: An Endocrine Society Clinical Practice Guideline, Endocrine Society, 2016, DOI:10.1210/jc.2016-2118