Hello @martyn, Welcome to Connect. It can be terrifying at first but the good news is that here on Connect you have a lot of folks that have experience with it and can be a great help to you for navigating what I like to call Mr. Ugly (PMR). There are alternative treatments but not sure I would want to manage it without steroids or an alternative medication. I've had 2 occurrences, six years apart and both treated with prednisone successfully but everyone is different when it comes to PMR, especially if you have multiple autoimmune conditions.

@dadcue posted a video in the following discussion that I found helpful if you want to learn more about the condition.
-- Comprehensive Overview Of PMR: https://connect.mayoclinic.org/discussion/comprehensive-overview-of-pmr/

I did have the weight gain side effects during my first PMR flareup taking prednisone but the second time around I was more aware of it and made a few lifestyle changes to help with that side effect - https://www.healthline.com/health/polymyalgia-rheumatica-diet. You mentioned a four day steroid test. Can you expand on that? What dosage of prednisone is used?