Gigi Hadid
Gigi Hadid tweeted about receiving treatment for Hashimoto's disease. Stuart C. Wilson/Getty Images

Gigi Hadid has spoken out about how Hashimoto's disease has changed her body, claiming she was criticised for losing weight.

The 22-year-old model wrote in a series of tweets that she has lost weight since she was diagnosed with the autoimmune disease.

Hadid wrote that she was previously criticised for being "too big" when she entered the modelling industry aged 17, and explained that she was experiencing inflammation and water retention at the time.

She added that since being diagnosed with the condition and "properly medicated", her symptoms have eased and she has appeared to lose weight.

Hadid also highlighted that her diet hasn't changed, and that she feels "healthier internally".

"I will not further explain the way my body looks, just as anyone, with a body type that doesn't suit ur 'beauty' expectation, shouldn't have to," she said.

In 2015, she slammed critics that saw her body as a deviation from the 'straight size' industry standard.

"Yes I have boobs, I have abs, I have a butt, I have thighs, but I'm not asking for special treatment....Your mean comments don't make me want to change my body," she wrote.

So what is the condition that Hadid was diagnosed with?

What is Hashimoto's?

Also known as Hashimoto's thyroiditis and Hashimoto's disease, it is an autoimmune disorder.

The disease causes the body to attack the thyroid gland, which secretes two hormones that help to regulate metabolism.

Hashimoto's causes it to swell and become damaged, according to the NHS. Over time, this affects the gland's ability to make hormones.

What are the symptoms?

By disrupting how the thyroid gland works, the condition can cause a person to experience fatigue, weight gain and dry skin.

A person with Hashimoto's might also develop a goitre, or lump in their throat. However, it can take years to diagnose because it develops slowly.

Who is at risk?

Scientists do not yet understand why some people develop Hashimoto's. However, it is most common in women aged between 30 to 50-years-old, and is sometimes hereditary.

How is it treated?

While it can't be cured, the symptoms of Hashimoto's can be managed with medication. In rare cases, surgery may be required to remove the goitre if it becomes uncomfortable or cancerous.