Down's Syndrome and facial hair

I’ve been seeing more and more people afflicted with Down’s Syndrome recently (and I also just finished rereading Dreamcatcher by Stephen King), and I’ve noticed something: Not ONE of them has had facial hair.

Is there some genetic predisposition that excludes a person with Down’s Syndrome from ever developing facial hair?

I’ve seen a couple with a little bit of dark peach fuzz but none with real facial hair. mentions low levels of thyroid hormone as a feature of Down syndrome. I’m not sure if that contributes to facial hair or not.