8 yr old male lakeland terrier has developed a bald patch on its back.

Vet has suggested a poss thyroid gland disorder or kidney problem? Toilet habits normal although seems to pass quite a lot of urine first thing in the mornings. Dog is exercised twice daily, eats and drinks as normal - recently we have been adding cod liver oil to his food. Still frisky and likes to play but somewhat reluctant to come out of his kennel for his first walk in the morning. Anyone with dog exhibiting same problems? Thanks JB NorthernIreland.