Gigi Hadid says she is suffering from Hashimoto's disease.

Gigi Hadid, one of the world’s most popular models, has shared that she is suffering from the thyroid condition Hashimoto’s disease and says the condition lead to dramatic weight loss throughout the year.

“My metabolism actually changed like crazy this year,” Hadid told Elle earlier this week. “So for the VS [Vicotoria’s Secret] show I didn’t want to lose any more weight.”

The lifelong autoimmune condition sees the body’s immune system cells attack the thyroid gland and ultimately destroy thyroid tissues, which limits the body’s ability to create hormones.

Hashimoto’s is slow-moving and is generally treated with medication.

Despite leaving its sufferers fatigued and sluggish, 21-year-old Hadid has refused to take a break, explaining, "I feel that pressure of not taking time for yourself because you don't want it to affect your professionalism."

It's not the first time Hadid has had to defend her physicality, receiving hateful comments about being both too fat and too skinny.

In 2015, Hadid wrote an open letter to people shaming her for being "too heavy", writing, "Yes I have boobs, I have abs, I have a butt, I have thighs, but I'm not asking for special treatment...if I didn't have the body I do, I wouldn't have the career I do."

In August of this year, the model was once again forced to defend her looks, this time for being too skinny.

“It’s called growing up,” she wrote in a response to a negative social media comment in August. “I loved my body as a 17-year-old athlete and I love my body now.

"Yes, I’ve lost some ‘baby fat,’ but muscle mass from my intensive volleyball training in high school has changed over the years into lean muscle from boxing, and work stress can have its affect [sic], but purposefully changing my body has never been my thing. I still eat what I want, I’m still strong, and I’m still healthy."

Hadid's younger siblings and fellow models Bella and Anwar, and mother Yolanda Foster all suffer from Lyme disease, which affects the body's organs and leaves sufferers with fevers, headaches, and fatigue.