Figure 5. Plasma ACTH in Cushing's syndrome subtypes.

Plasma ACTH concentrations (pg ml⁻¹) in patients with ACTH-dependent Cushing's syndrome (Cushing's disease (pituitary corticotroph adenomas) and ectopic ACTH) and ACTH-independent Cushing's syndrome (adrenal tumour). Note that plasma ACTH is within the reference range (blue shading) in many patients with Cushing's disease and that, on average, patients with ectopic ACTH have very high plasma ACTH. Furthermore, patients with adrenal autonomy usually have suppressed plasma ACTH due to increased cortisol negative feedback suppression of the hypothalamus and pituitary. To convert to pmol l⁻¹, multiply pg ml⁻¹ by 0.2202. From Raff et al. (2014) with permission.