I’ve been tracking this pattern for a few mos now, and it’s become my early warning sign. The cold hands don’t happen randomly - they show up about 2-3 days before the brain fog gets genuinely bad. My endocrinologist said they’re probably unrelated, which frankly frustrated me, but when I checked my free T3 and free T4 on those specific days, the drop was there. When my T3 bottoms out, hands go cold first, then comes the fog.
I think what’s happening is the circulation issue comes before the cognitive one. Cold hands are a metabolic slowdown. Brain fog is what living inside that slowdown feels like. They’re not separate symptoms, they’re the same thing at different intensities.
The frustrating bit is that some endos only check TSH, which can stay “normal” whilst free T3 actually tanks. If you’re on levo alone (no T3 support), and you’re noticing this pattern, ask for a free T3 check when your hands get cold - don’t wait for ur scheduled appointment. By the time the fog shows up, you’re already a few days into it. Has anyone else worked out this timing pattern with theirs?