Adrenocortical hypertrophy: establishing cause and toxicological significance

The primary cause of adrenocortical hypertrophy is increased adrenocorticotrophic hormone (ACTH) stimulation. In toxicology studies, such a condition can arise as a result of the stress response, but it may also occur due to deficient glucocorticoid feedback regulation of ACTH due to toxicity to the adrenal cortex. This latter condition is defined as adrenocortical insufficiency and represents a serious adverse toxic effect on the function of the adrenal cortex. Adrenocortical hypertrophy may occur in the absence of other adrenocortical lesions such that a toxicopathological mechanism is not obvious, for example by pharmacological inhibition of steroidogenesis at the biochemical level. This review discusses the different aetiological factors and mechanisms producing adrenocortical hypertrophy. The need for further evidence in ascribing findings to stress is discussed, as is a protocol for establishing differential diagnoses between stress-induced and toxicity-induced adrenocortical hypertrophy, which is useful in cases where there are no other histopathological lesions in the adrenal cortex. It is concluded that all cases of adrenocortical hypertrophy require further investigation or evidence to ascribe such findings to either stress or adrenocortical inhibition/insufficiency, and that all cases of adrenocortical insufficiency (whether due to a histopathological lesion or reversible pharmacological enzyme inhibition) represent a serious adverse effect that must be properly considered in toxicological risk assessment.