Question about Thyroid

Hi friends, hope everyone is doing well today. So mom went in to her general doctor the other day. Good news is that her Cholesterol is down but her blood work showed a couple of things. She is very deficient in Vitamin D which is okay, she is now taking Calcium + Vitamin D but she tested for hypothyroidism...slow thyroid. Someone told me that this happens with radiation but I was curious if anyone else had this issue. I think this might explain why she wants to sleep so much. I thought maybe it was the chemo but 2 months later she is still sleepy and maybe the thyroid issue is contributing to that. She is also a bit colder which too i thought could be from the chemo but I know suspect that the thyroid is playing a role. So question is, does anyone know if there are supplements or herbs she can take to help specifically with thyroid and if you guys have any idea if this is temporary due to radiation exposure or this is permanent? The doc said she wanted to wait 6 weeks, see how the vitamins and minerals she has advised work and if in 6 weeks the bloodwork is the same then mom has to go on thyroid med. Anyway any insight into this would be great.
thanks
Renata