I have had high cortisol for three years off an on and I am 45. I have gotten my down before but then stress would send it back up again.
What has worked:
Take a B complex several times a day. I started taking 7 Keto Dhea and noticed it doesn't really lower cortisol but helps my liver and digestion.
Part of what I did before is to take 4 - 5 times a day and relax I used binaural beats meditation and The Healing Codes. Reminding my mind and my body I am calm now. This was a huge factor in lowering my cortisol. Also I just finished my 5th session with Terry Dodge doing NMT, a healing technique which has been great for me.
Sleeping 10 - 12 hours a day. If you can't sleep that long lie there and meditate.
Stop drinking alcohol, it raises cortisol (this is a biggy). No caffeine and stay away from simple carbs.
Excercise as long as it's under one hour helps lower cortisol not too intense.
Another powerful thing to bring my cortisol down was Relora and meditation audio brainwave entrainment and the Healing Codes. When I first started taking Relora a month ago it gave me a slight headache. Seems anything that shifts my homrones give me some kind of headache. I had to use Rhodiola to tolerate the Relora. Rhodiola will cancel out any cortisol lowering effects of anyting else but made me feel good. After 3 weeks I quit the Rhodiola and was able to take Relora without a headache. Yesteday I had to stop the Relora because I had hit a point that it was lowering my cortisol past the point I needed. It started making me drag so I guess it did it's job and I don't need it anymore.
Now I noticed I do get a little week at times I push myself too much. Another thing is that that when I stand up I get dizzy at times now. I been doing Sea Salt but also think I need to add potassium.