Steroids Not Significantly Affected by ACTH Stimulation Test
Aldosterone and mineralocorticoid function remain largely independent of ACTH stimulation testing, as aldosterone secretion is primarily regulated by the renin-angiotensin-aldosterone system (RAAS) rather than ACTH. 1
Mineralocorticoid Pathway
Aldosterone production is controlled by the RAAS and potassium levels, not by ACTH, making it functionally independent of the hypothalamic-pituitary-adrenal (HPA) axis that the ACTH stimulation test evaluates 1
In secondary adrenal insufficiency (hypopituitarism), patients continue to secrete aldosterone normally in response to renin despite having inadequate ACTH production and cortisol deficiency 2
This explains why patients with secondary adrenal insufficiency typically do not develop the severe electrolyte abnormalities (hyperkalemia, hyponatremia) seen in primary adrenal insufficiency, where both cortisol AND aldosterone are deficient 2
Glucocorticoids and ACTH Response
While the question asks about steroids not affected by ACTH, it's important to understand which ARE affected for clinical context:
Cortisol shows the most clinically relevant response to ACTH stimulation, with peak levels typically occurring at 30-60 minutes after administration 3, 4
Adrenal androgens (DHEA, androstenedione) are highly sensitive to ACTH, with DHEA being the most sensitive adrenal steroid to corticotropin stimulation 3, 4
17-OH-progesterone, corticosterone, and 11-deoxycortisol all increase significantly with ACTH stimulation, with corticosterone showing a 15-fold median increase compared to cortisol's 1.4-fold increase 5
Cortisone does not increase after ACTH stimulation, as it is primarily a peripheral metabolite of cortisol rather than a directly secreted adrenal hormone 5
Clinical Implications
When interpreting ACTH stimulation tests, focus on cortisol response for diagnosing adrenal insufficiency, as the 250-μg ACTH test is the recommended diagnostic standard 1, 2
Do not rely on aldosterone levels during ACTH testing to assess mineralocorticoid function—instead, measure renin and aldosterone levels separately under baseline conditions 6
In patients with suspected hypopituitarism and secondary adrenal insufficiency, expect normal aldosterone function despite impaired cortisol response to ACTH 2
Exogenous therapeutic steroids (dexamethasone, betamethasone, prednisone, prednisolone) will suppress the HPA axis and interfere with ACTH stimulation testing, requiring discontinuation before testing 1, 7