I thought I had chronic fatigue but it turned out I needed thyroid meds. While my CCC doctors were top notch on Cancer, for related issues like Thyroid - "not so much". I was not only extremely tired but also froze for two years, even in summer, and kept a winter coat on in air conditioned places yet I was constantly told: "Your TSH levels are normal" and I did not ask for the actual numbers or test results. Turns out however there is controversy over what is the right TSH level with labs having a 5.5, a 4.5 even though endocrinologists who went to Medical school the 21st Century consider 3.0 as the highest acceptable level. Before TX, I had a TSH of 1.6 and after TX it shot up to 4.3. My TSH level went down to 1.48, now that I am "on the pill", I am finally warm again. Plus my energy is back Of course there could also be nothing wrong at all with his thyroid . But it's a simple blood test. Check back on his back records to see if he has a pre radiation TSH level to shoot for.
Best wishes
Charm