The association between cortisol and hypertrophy may be correlational rather than causal.

“and the interpretation is again is it that cortisol is producing hypertrophy or is it cortisol is in response to the stress that is producing hypertrophy so that's again this seems paradoxical because people see an association they automatically think well there must be a cause there not necessarily at all these two things are happening in parallel so what it means is the resistance training session that is going to produce the most amount of stress the most amount of adaptation is probably going to produce the most cortisol and possibly the most hypertrophy if it's repeated right”