Karen Belz
Updated December 09, 2016
Getty Images / Stringer

By now, you probably know that many diseases aren’t obvious at first glance. It’s probably why fans were in the dark about Gigi Hadid’s thyroid disease, which she’s been battling for roughly two years. While treatment is typically effective, the disease itself — called Hashimoto’s Disease — is pretty inconvenient.

Hashimoto’s Disease is often present when your immune system attacks your thyroid. Symptoms vary, but according to Mayo Clinic, some of the most common are fatigue, puffiness, hair loss, and aches and pains.

Hadid opened up about the illness at Reebok’s recent #PerfectNever event in New York City.

Hadid is in pretty good company. After all, Hashimoto’s Disease has been pegged as being the most common thyroid disease around, and approximately 14 million people are affected. In fact, celebrities like Victoria Justice, Zoe Saldana, and Gina Rodriguez have admitted that they also have it.

Two of the main factors that cause Hashimoto’s Disease are genes and hormones — so for many, it’s the luck of the draw.

It’s just good when celebrities speak out about silent illnesses, since it helps others who may be suffering realize that they’re not alone.