I found this article about low cortisol both interesting and unconventional, in that it advocates high doses of HC (40-60 mg daily) in persons taking DHEA and thyroid hormone.
I have read about Plenadren, but I have no idea if it's readily available yet. It seems great, as it contains slow-release cortisol, as opposed to conventional HC which causes your levels to peak to supra-physiological levels within an hour, and then drop drastically.