What additional tests should be run on a patient with known secondary adrenal insufficiency?

Additional Testing for Known Secondary Adrenal Insufficiency

In patients with established secondary adrenal insufficiency, you should screen annually for associated autoimmune conditions (thyroid dysfunction, diabetes, vitamin B12 deficiency, celiac disease) and evaluate for other pituitary hormone deficiencies if not already done. 1

Screening for Other Pituitary Hormone Deficiencies

Since secondary adrenal insufficiency indicates pituitary or hypothalamic dysfunction, you must evaluate for additional pituitary hormone deficiencies if this hasn't been completed:

• Measure thyroid function (TSH, free T4) to assess for central hypothyroidism, as this commonly coexists with ACTH deficiency 1, 2
• Assess gonadal function with LH, FSH, and sex hormones (testosterone in men, estradiol in women) to identify hypogonadotropic hypogonadism 3
• Check IGF-1 levels to screen for growth hormone deficiency, which frequently accompanies other pituitary hormone deficits 3
• Measure prolactin levels to evaluate for hyperprolactinemia or prolactin deficiency depending on the underlying pituitary pathology 3

Critical pitfall: If you identify concurrent hypothyroidism, you must start corticosteroids several days before initiating thyroid hormone replacement to prevent precipitating adrenal crisis 1, 2

Annual Screening for Autoimmune Conditions

Even though secondary adrenal insufficiency is not autoimmune in origin, patients require annual screening for associated autoimmune disorders:

• Thyroid function tests (TSH, free T4, thyroid peroxidase antibodies) annually to detect autoimmune thyroid disease 1
• Fasting glucose and HbA1c to screen for diabetes mellitus 1
• Vitamin B12 levels to identify pernicious anemia 1
• Tissue transglutaminase 2 antibodies with total IgA if the patient has frequent or episodic diarrhea to screen for celiac disease 1

Baseline Electrolyte and Metabolic Assessment

• Basic metabolic panel (sodium, potassium, glucose) to establish baseline values, though hyperkalemia is not expected in secondary adrenal insufficiency since mineralocorticoid function remains intact 1, 4
• Morning cortisol and ACTH levels are already diagnostic in known cases (low cortisol with low or inappropriately normal ACTH), so repeat testing is unnecessary unless assessing recovery 1, 4

Imaging Studies

• Pituitary MRI with gadolinium contrast if not already performed, to identify structural lesions (adenomas, hemorrhage, infiltrative disease) causing the ACTH deficiency 3, 5
• Adrenal CT imaging is NOT indicated in secondary adrenal insufficiency, as the problem lies in the pituitary/hypothalamus, not the adrenal glands themselves 1

Monitoring Adequacy of Replacement Therapy

• Do not routinely measure cortisol levels in patients on established glucocorticoid replacement therapy—the diagnosis is already confirmed, and cortisol assays will measure both endogenous and exogenous steroids, making interpretation meaningless 1
• Assess clinical symptoms of under-replacement (fatigue, nausea, weight loss, morning symptoms) or over-replacement (weight gain, insomnia, mood changes, cushingoid features) 1, 4
• Monitor for signs of glucocorticoid excess including blood pressure, weight, glucose control, and bone density if on long-term therapy 6

Patient Education and Safety Measures

While not "tests" per se, these are mandatory assessments of patient preparedness:

• Verify the patient has a medical alert bracelet indicating adrenal insufficiency 1, 2, 4
• Confirm the patient possesses an emergency injectable hydrocortisone 100 mg IM kit with documented self-injection training 1, 2, 4
• Document patient understanding of stress-dose protocols (doubling or tripling oral doses during illness, when to use injectable hydrocortisone) 1, 2, 4
• Ensure endocrine consultation is established for ongoing management and pre-operative planning 1, 2

What NOT to Test

• Do not perform ACTH stimulation testing in patients with confirmed secondary adrenal insufficiency unless you are specifically assessing for HPA axis recovery after discontinuing exogenous glucocorticoids 1, 3
• Do not measure 21-hydroxylase autoantibodies—these are only relevant for primary adrenal insufficiency, not secondary 1
• Do not check aldosterone or renin levels—mineralocorticoid function is preserved in secondary adrenal insufficiency, so fludrocortisone is not needed 1, 7, 4