There are lots of videos available - some of which are excellent; others rather less so.
I found Handwritten Tutorials suited my brain, my way of understanding. Further, there is no charge for them and they are simple. That is, the work has gone into the basic design and thoughtful presentation - not whizzy graphics, computer-generated whizzy things, loud whizzy music, etc.
I suggest you start here:
At the bottom of the page are several playlists which might make it easy to work through sensible sets of videos.
Or go on to the all videos page:
youtube.com/user/harpinmart...
There are some specific videos on thyroids and on the immune system as well as the adrenals - and lots else.
For example, Thyroid Hormone Production:
youtube.com/watch?v=2qYBzjt...
Feel free to add your own preferred videos as replies.
Noelnoel