I need to clarify some of my and the other comments. When I spoke of a relative steroid dependence, I meant that in times of physical crisis the adrenal glands might not be able to respond promptly with the large doses of cortisol they need to produce.
It is impossible for me to say whether one day a week would do this. The current wisdom is to be very conservative in this. And the concern is not the total dose, but the frequency of use. Once a week is frequent, but just one day may not cause steroid dependence at all. I certainly don't know.
However, if it is a possibility, then it would not hurt to have a little extra - or a lot extra - in times of severe physical stress. I would not take the chance.
I wrote a Health Page on this when one of our members - who had been taking steroids for many months - went into Adrenal Crisis when she stopped them: "Steroids - Friend and Foe.
http://www.medhelp.org/health_pages/Multiple+Sclerosis/Steroids---Friend-and-Foe/show/365?cid=36
As far as the comment that steroids destroy the immune system over a long period of use. This is not true. When used continuously for a prolonged period - many days, the immune system is certainly "suppressed," but not destroyed. This can allow certain infections to take hold and be far, far more serious than they would be normally. TB can be reactivated, bacterial infections can become life threatening, and some viral infections that should be mild can become life-threatening.
I do not think, but am not sure, that once a week at the modest dose of 20mg would be that suppressive to the immune sytem, leech calcium from the bones, nor make you severely steroid-dependent (from the adrenal gland perspective). But, there are other things also to consider. I have been told repeatedly that the cataracts, which steroids are known to cause, are cumulative exposure-dependent, along with being dose-related. This means that the more days you have exposure to them, then more likely you are to develop cataracts.
I also think a second opinion, from an endocrinologist, wouldn't be a bad idea. But, wearing a ID tag is harmless and could be very beneficial.
Quix