My Son Is 18 Years And Has Always Had An

My son is 18 years and has always had an issue with his body temperature, we jokingly call him a portable heater. its so bad that we could not let him ride in the front seat because he fogs up the windows. He is always complaining about being hot even when the rest of the family is wearing sweaters. I took him to his doctor and they said there is nothing wrong with him. But I wonder, I keep the temperature in the house at 65 and so he can sleep better but he still uses two fans. Is this normal??