Thank you @boatsforllife for very clearly describing your symptoms which are almost identical to mine and which I had for many years. I am 71, also have Hashimoto's hypothyroidism and had blamed my symptoms on that, being a bit overweight and being out of shape etc. My family thought I was just making excuses. For years, I would tell my husband that I couldn't walk after just eating and forget hills, inclines and stairs whether I had eaten or not. What I didn't realize was how much avoidance I was unknowingly and instinctively practicing. I actually watched my mother behave much the same way (she lived to 90 but was very inactive) and now know she likely had the same disease although we'll never be sure. Since diagnosed this year and started on Camzyos in August, my symptoms have lessened but thanks to another posting on this site, I've learned that my gradient really only increases with exertion, so a stress echo was vital in establishing this.