D cat is 13, neutered male and an indoor cat who is allowed out in the garden under supervision as we live on a main road. He is a shorthair but with an extremely thick coat and has been very moulty since we got him as a kitten. He has been shedding more in the last week and has taken offence to a friend who has stayed for a couple of nights, mewing and attacking her. Friend is a regular visitor and is normally the only one who he will allow to stroke his belly and cuddles up with her on the sofa, but has attacked her legs and bitten through her jeans twice in the last week. He is eating and toileting as normal but has been grumpy with us too. Nothing in the house has changed, his routine has not changed, his food and litter has not changed but he is acting a bit out of character. Nothing indicates that he is ill, should we get him checked or could it just be the heat?