Hello, as mentioned above, Thyroid problems are par for the course after head and neck radiation. Kris's Thyroid failed about 12 months after his rads. Treatment is simple and easy. A daily pill or two and a blood test every few months to check levels. This should help with the energy levels and hopefully you won't find the Winter too cold either. Kris was always freezing until his Thyroid was sorted..
Take care, Tammy.

Caregiver/advocate to Husband Kris age 59@ diagnosis
DX Dec '10 SCC BOT T4aN2bM0 HPV+ve.Cisplatin x3 35 IMRT.
PET 6/11 clear.
R) level 2-4 neck dissection 8/1/11 to remove residual node - necrotic with NED
Feb '12 Ca back.. 3/8/12 total glossectomy/laryngectomy/bilat neck dissection/partial pharyngectomy etc. clear margins. All nodes negative for disease. PEG in.
March 2017 - 5 years disease free. Woohoo!