A disease of the thyroid gland (underactive) that effects mostly females: symptoms include slow metabolism, dry skin, sleepiness, dry hair. It can be hereditary. It may be caused by your body attacking your thyroid (Hashimoto disease), or it may be inexplicable.

I finally went to the doctor and was diagnosed with it after a semester of truly excessive naps & other strange sleepiness. They subscribed synthroid, but as i didn't notice any changes after a couple of months (and I resented having to take drugs to be "normal"), I haven't taken it since.

I am now used to being sleepy. I hide it well.