Question. If I'm reading this correctly you're doing a little over 400 mgs test when you pulled this BW? If so your serum level is horrible. It should be way higher.
Also, when it comes to SHBG I'm glad you tested it. You need to keep an eye on things as low SHBG combined with cholesterol issues is a marker for metabolic syndrome. Google it. Yes, added test will suppress SHBG and it also will decrease due to aging. That said, your number is low imho. Next time you pull BW (off cycle) keep an eye on it as well as your CRP level. I'd also suggest an advanced NMR or VAP Lipo profile which breaks down your chol / LDL and gives a much more concise picture.