Patients with initially high baseline morning cortisol (>300 nmol/L) undergoing dexamethasone-based chemotherapy exhibit a greater downward trend in cortisol levels over time compared to patients with lower baseline cortisol levels, although this difference is not statistically significant and may be attributable to regression to the mean.

A strong synthetic steroid enters the body and binds to receptors in the brain and pituitary gland, which tells those areas to stop sending signals to the adrenal glands. Without those signals, the adrenal glands produce less cortisol. People who start with very high cortisol levels experience a larger drop because their system is more active and responds more strongly to the shutdown signal.