Glucocorticoid and mineralocorticoid production in hormonally silent adrenocortical tumor tissue in dogs

Background No consensus exists regarding the monitoring and therapeutic approach to adrenal tumors (ATs) discovered incidentally by diagnostic imaging, when standard endocrine testing yields negative results.Hypothesis/Objectives To evaluate tissue concentrations of adrenocortical steroids in hormonally silent adrenocortical tumors (SATs) in dogs.Animals Fourteen dogs with SATs (12 unilateral, 2 bilateral), 11 dogs with cortisol-secreting adrenocortical tumors (cs-ACTs) and 10 healthy dogs.Methods Observational study. Diagnosis of SAT was based on finding an AT on diagnostic imaging, negative endocrine function tests, and histopathological and immunohistochemical confirmation. Adrenocortical steroid tissue concentrations were measured by liquid chromatography with tandem mass spectrometry and compared between SATs, cs-ACTs, and normal adrenals (NAs).Results Hormonally silent adrenocortical tumors exhibited higher median tissue cortisol (3.62 ng/mg, range 0.05-18.1) and 21-deoxycortisol (0.08 ng/mg, range 0.00-0.44) concentrations than NAs (cortisol 0.38 ng/mg, range 0.01-1.90; 21-deoxycortisol 0.01 ng/mg, range 0.00-0.03; P = .04 and P = .001, respectively), and these concentrations were not significantly different between SATs and cs-ACTs. Furthermore, SATs' median tissue concentrations of mineralocorticoid precursors corticosterone (2.15 ng/mg, range 0.01-14.1) and 18-OH-corticosterone (0.70 ng/mg, range 0.00-4.89) were higher than in NAs (respectively 0.19 ng/mg [range 0.14-0.54] and 0.05 ng/mg [range 0.01-0.33]; both P = .01) and not different when compared to cs-ACTs.Conclusions and clinical importance This study on tissue metabolomics in ATs in dogs demonstrates comparable tissue concentrations of specific glucocorticoids and mineralocorticoids in SATs and cs-ACTs. This implies that some SATs are not hormonally silent, prompting further studies on diagnostics, treatment, and monitoring recommendations.