Great question to the community - in addition to checking in with his doctor/care team and even getting a second opinion from another doctor if you'd like to about hyperthyroidism with treatment and options / whether to continue treatment / how to treat the hyperthyroidism, these links may help too - it is recommended to have thyroid monitored with Keytruda, and chemo may also cause side effects:
https://lungcancer.net/medications/chemotherapy
this community member also shared a story inclusive of noting thyroid changes after treatment: https://lungcancer.net/stories/lung-cancer-journey
Thinking of you and your dad. Please do keep us updated.
Warmly,
Margot, (LungCancer.net Team)