Adrenal cortex is an essential portion for life and its function can be affected by many chemical agents and drugs. In this investigation, effect of silymarin, a flavonoid, on adrenocortical structure of male dexamethasone (Dexa) treated hamsters were studied by histological and unbiased stereological techniques. The results showed that the adrenal gland mass of Dexa treated hamsters was significantly decreased in comparison to animals that received Dexa with silymarin (Sily). It was also obtained that there are no significant difference in the zona glomerulosa (ZG) volume and cell number among examined groups. The volume of the cortex, zona fasciculata (ZF) and zona reticularis (ZR) and cell number of these regions were significantly reduced in Dexa treated hamsters compared to controls (P<0.05), whereas in Dexa + Sily treated animals, this reduction was not observed. Histological results showed that tissue structure of ZF and ZR was same in all groups except Dexa treated animals. In the hamster that received Dexa, a sever hyperemia was observed in the adrenal cortex. Finally it can be concluded that silymarin seem to be a suitable protective drug for side effect of glucocorticoid therapy in adrenal glands.

Key words: Adrenal cortex, dexamethasone, hamster, glucocorticoid, silymarin, unbiased stereology.