I think B's got it. We reach a point where we have to face our mortality, and look back on a life lived for the convenience of others, but lacking for ourselves.
Males in my family tend to die in their late 60s, so turning 60 produced some serious introspection for me. When I hit 62, I recall just sitting there thinking "Just 5 years to go. I can keep my secrets for just a few more years." Then, something changed, or something snapped, and I couldn't go on with this.
My wife kept putting off plans for travel, "Oh, we'll do that in a few years. Maybe in our 70s." I know what happens to people who plan like that. It never happens. Medical issues, aging, increasing frailty all conspire to thwart those sorts of plans. I didn't think I'd be alive for them. I barely felt like I was alive right now. In fact, why bother continuing? I'd known what I was exactly (a transwoman in hiding) for 30 years, and it wasn't getting any better.
The dysphoria begat depression, and the depression made the dysphoria harder to handle. It was a downward spiral that ended with me hooking a hose into the car exhaust before the catalytic converter and sealing the interior, then me holding the pills in my hand that I had determined would depress my respiratory reflex and keep me comfortable once I started the engine.
I called a hot line instead, they talked me down, and I got help. After my first appointment I got rid of the exhaust hose and fittings I had built.
I'm pretty sure testosterone levels didn't play into this. My level just before starting HRT was 650, pretty much normal for my age. One culprit to altering my mental state might have been prolactin. I do have a 'microprolactinoma', and a significantly elevated level compared to the male normal. Extrapolating from the recent level measurements, it has probably been rising 7-8 months, and was significantly high starting a month or so before I hit bottom. It might have given me a nudge over the edge. (Prolactin in males tends to counteract testosterone pretty strongly.)
