Yeah, it sounds like something could be wrong with his thyroid. Most types of thyroid cancer arent’ the type that spread…. just the nature of how the thyroid works. There are the parathyroids as well and they are bit trickier, causing odd things to happen with calcium levels, from what I remember.
Thyroid cancer or nodules can increase the production of T4 and T3 and cause loose bowels, sweatiness, shaking and hair loss and I’ve even heard of dental caries because the mouth is dry and it causes an abundance of bacteria and they decay the teeth in the dry environment. If it does turn out to be an over active thyroid, encourage him to see a dentist within the year.
It’s a very quick test to see how his thyroid levels are doing. If there are anomalies, to get a better picture, they do an Iodine uptake test with a tiny amount of special radioactive iodine.
Encourage a doctor’s visit this week ASAP. He may even have to see a specialist, so the sooner the ball gets rolling, the better!