Objective: Large response of steroid precursors, including 17-hydroxyprogesterone, to adrenocorticotropic hormone (ACTH) has been described in adrenocortical tumors, suggesting the existence of intra-tumoral enzymatic deficiencies. This study aimed to compare steroidogenesis enzymes activity in unilateral and bilateral benign tumors using serum steroid profiling in liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) in the basal state and after ACTH 1-24 stimulation.
Design and methods: A serum profile of seven consecutive adrenal steroids was determined in LC-MS/MS in the basal state (T0) and after ACTH 1-24 stimulation (T60) in 35 patients with bilateral adrenocortical tumors (BL), 38 patients with unilateral tumors (UL) and 37 control subjects (CT). Response amplitude of each individual steroid was evaluated by T60/T0 ratio, whereas enzymatic activity was assessed by the downstream/upstream steroid ratio. Adrenal volume was quantified by a semi-automatic segmentation method.
Results: For the seven steroids assayed, the amplitude of response to ACTH was higher in BL than in UL and in CT. The difference between BL and UL persisted even after matching patients on adrenal volume. On glucocorticoids pathway, enzymatic activity of CYP11B1 was significantly decreased in BL (78.3 (43.1-199.4)) in comparison to both UL (122.7 (13.8-228.4), P = 0.0002) and CT (186.8 (42.1-1236.3), P < 0.0001). On mineralocorticoids and androgens pathways, the enzymatic activity of CYP11B2 and CYP17A1-17,20 lyase was also lower in BL than UL and CT.
Conclusions: Decreased activity of distal steroidogenesis enzymes CYP11B1, CYP11B2 and CYP17A1-17,20 lyase, responsible for an explosive response to ACTH of upstream precursors in bilateral tumors, limits the synthesis of bioactive steroids, in particular cortisol, despite the increase in adrenal mass.
Significance statement: Activity of distal steroidogenesis enzymes (CYP11B1, CYP11B2 and CYP17A1 on glucocorticoids, mineralocorticoids and androgens pathways, respectively) is decreased in adrenocortical benign tumors. This decrease is more pronounced in bilateral lesions and seems to depend more on the nature of the lesion than on the increase in adrenal volume. It is responsible for the explosive response to ACTH of steroid precursors located upstream of these enzymes. It probably allows bioactive steroids, particularly cortisol, to stay in the normal range for a long time despite the increase in adrenal mass.
Keywords: ACTH; LC-MS/MS; adrenocortical tumors; primary bilateral macronodular adrenal hyperplasia; steroids.