Interesting; I do eat a lot of fish (although not very much canned tuna). I most often eat shrimp and shellfish, when I dine out. I'll ask my doc about mercury poisoning -- I had never even considered that.
I will keep you posted on my new blood work numbers when they come back from the lab. The tests I've ordered are for: thyroid, prolactin, DHEA, testosterone (free & total), SHBG, as well as a chem panel with lipids and CRP.
On the subject of shellfish, here's another anomaly: one night recently I ate a large plate of raw oysters for dinner, and later experienced very firm nocturnal erections and very sexual dreams (practically to the point of nocturnal emission). This, when it's very rare for me to have a nocturnal erection at all, and never a firm one. I never put much stock in oysters' reputation as an aphrodisiac, but I am now convinced there is something to it. Unfortunately, the effect only lasted one night. Needless to say, I've now purchased a bottle of oyster extract capsules. I'd let you know if they seem to do much.