Gigi Hadid has had a very successful year as the 21-year-old recently appeared on Victoria’s Secret Fashion Show in Paris. The star was also named as the Model of the Year at the 2016 British Fashion Awards earlier this month, and it appears that there’s no stopping Hadid from conquering the fashion world. However, the model recently revealed that she is currently battling an autoimmune disease, and that her medication is to blame for her slimmer figure.

Speaking with Elle, Gigi Hadid said that her metabolism has changed a lot this year, and that she has Hashimoto’s disease.

“It’s a thyroid disease, and it’s now been two years since taking the medication for it, so for the VS show I didn’t want to lose any more weight,” she explained.

Hadid’s revelation explains her slimmer figure, as earlier this year, a fan blasted the model for her new body, accusing her of changing to fit in with the weight-obsessed modeling world. Yahoo Style reports that Hadid replied to the fan and said that her new body was all part of growing up.

“Bodies change as girls become women, just as my mom’s body changed at the same time,” Hadid wrote.

According to Insider, Hashimoto’s disease causes the immune system to make antibodies specifically to attack the thyroid, which is a gland found at the back of the neck. The thyroid secretes hormones that regulate metabolism, and women are more likely to develop the disease than men.

Gigi Hadid is no stranger to dealing with health issues, as her own mother, Yolanda Hadid, has been battling Lyme disease since 2012. The model’s siblings, Bella and Anwar, are also suffering from the debilitating disease.

It appears that the Maybelline model is in control of her health condition as she was spotted looking healthy at the Victoria’s Secret Fashion Show and other recent public appearances. In addition to working out, Jobs & Hire previously reported that Hadid follows a healthy diet, and indulges in the occasional burger or ice cream as a treat.