I haven't heard of this scenario specifically, but would be completely unsurprised if opioid abuse didn't result in low testosterone levels, nor would I be surprised to find out that low levels of it could cause the sorts of side-effects you're talking about.
Also, has your fiance had his thyroid checked? I know it's REAL common for opioids to screw up the levels of whatever hormones the thyroid usually puts out, and this has similar effects to what you're talking about... or ... maybe testosterone is one of them, and we're really talking about the same thing ...