Endocrine Abstracts

Background: Patients with adrenal incidentaloma (AI) and cortisol levels of 50-138 nmol/l on overnight dexamethasone suppression tests (ONDST) may have “mild autonomous cortisol secretion” (MACS). MACS is associated with increased morbidity, including osteoporosis, but this is infrequently systematically evaluated. We compared fracture risk and fracture prevalence in patients with AI, both with and without MACS.

Methods: Data were collected retrospectively on patients with an AI and ONDST. Demographic data, biochemistry and fracture prevalence were recorded. FRAX risk and corresponding National Osteoporosis Guidance Group (NOGG) risk category were calculated. Statistical analysis was conducted using PRISMv9.3.1.

Results: 498 patients with AI were evaluated (49.3% male), mean age 65.6±11 (SD) years. 202 patients had evidence of MACS, the remainder had a suppressed cortisol. Patients with MACS had a mean age of 69.3±11.2 years vs 62.7±10.8 in those without MACS. There were no other significant differences between the groups. 15.6% of MACS patients had a previous fragility fracture vs 9.8% of patients without MACS (P=0.055). 33.8% of patients with MACS were classified as medium, high or very high-risk according to NOGG vs 24.4% of patients without MACS (P=0.022). Mean FRAX risk of major osteoporotic fracture over the next 10 years in patients with MACS was 9.4±8.5% compared with 6.8±5.2% in those without MACS, (P<0.0001). Mean FRAX risk of hip fracture was 3±3.4% in the patients with MACS vs 1.8±2.6% in those without MACS (P<0.0001).

Conclusion: One third of patients with MACS warranted further bone health evaluation. Patients with AI and MACS had higher risk of fracture and trend to increased fracture prevalence, compared to patients with AI and no evidence of MACS, although age may be a confounder. Therefore, we recommend routine FRAX evaluation in all patients with AI and MACS to guide further bone management.