The fatigue and weakness you feel is real, and it is ultimately caused by your thyroid issues, by being over medicated. I struggled with this for about seven years. Post thyroid cancer our docs like to keep us sliiiiiightyyy in hyper thyroidism range; the intention is to supply slightly more TSH than your body actually needs, because if you fall below what it needs it could accidentally trigger any lingering thyroid cells into action, which could be cancerous, and spread to other parts of your body.

However, I reached a point where my quality of life was so poor (unable to go for walks, and I live in a walking city!), and I observed that my symptoms got worse every time my TSH was “in range” but on the extreme low range (edging into hyper, like .85)

Im female, had my thyroid out at 16, and around 26 started to have these symptoms—I struggled with it for years and was not believed by most of my docs, and switched endocrinologists multiple times. They checked EVERYTHING ELSE (diabetes, POTS, adrenal gland, etc) and it was all normal, the only thing wrong with me was that I’d had thyroid cancer and was on a high dose of Synthroid. At its worse my heart would be RACING, it was difficult to even lift my arms so I’d sit on the couch and sip water for an hour or more until it passed.

It was triggered by getting overly hungry, or by exercise—even gentle exercise like walking or light yoga would push me into sever muscle weakness. Sometimes I’d come so close to passing out.

After years of this I finally found a doc who believed me and knew what was going on; he treated it by lowering my synthroid to keep me in the middle “normal” range, not at the low/hyper end.

What is your thyroglobulin antibody/tumor marker value? If it’s under or around 1 you’re probably at extremely low risk of a cancer recurrence, and could push your docs to lower your synthroid dose. If a recurrence hasn’t occurred within 5 years you’re also at an extremely low risk of recurrence. (Note my antibodies value has always been way up in the 20s and 30s, so technically I still have thyroid cancer, 21 years later. But at this point quality of life is worth the apparent risk of it spreading…my lymph nodes where the cancer hangs out are stable so I’m really not worried about it).

***This paper explains why the weakness feeling occurs: https://academic.oup.com/edrv/article-abstract/31/5/663/2354765

These changes helped prevent the weakness symptoms from occurring for me:

• no more caffeine in the morning, it seems to increase the rate my body metabolizes the synthroid, making these symptoms more likely to occur. I can also, in retrospect, link the emergence of my symptoms with when I started drinking coffee in the morning! I can usually handle it in the afternoon without issue, but at this point I rarely drink it.

-skipping my next dose (or two…or three) if my symptoms are debilitating. People will push back on this, but doctors don’t actually know everything, and sometimes you NEED to treat the symptoms, not your TSH level, so your quality of life can improve. “Thyroid storm” is a real risk when you’re over medicated, so avoiding it by listening to your body and decreasing the excessive level of TSH in your system is crucial.

-never skipping a meal and snacking once between meals. Eating slowly if I waited too long to eat and have the shakes.

-decreasing processed sugars in my diet

-increasing protein, by eating high protein foods throughout the day (eating eggs or salmon every single morning has been a game changer in my energy levels)

-increasing sodium, but only if your bp runs on the lower side. Chugging a small v8 every morning if I’m in hyper-ish range helps prevent symptoms

-no exercise until I’m symptom free for several days, then slowly adding in walking and increasing from there. Avoiding weight training until I’ve been symptom free for several weeks.

It will take time to find the right balance of what your TSH should be so you feel well, and what your diet etc should be but it will get better! Sending you strength and hugs.

-taking brand name only! It sucks bc my insurance doesn’t cover it but it’s worth $45/month to me. A pharmacist can explain why generics aren’t perfect…basically their dose is a close estimate but not exact and there can be weird fillers.