The former American Idol finalist, 20, made the announcement about her health during a radio interview in America on Monday (08Aug16), revealing she was diagnosed in April (16) and underwent surgery to remove the thyroid and other cancerous lymph nodes.

Jax also told NJ 101.5 host Bill Spadea that she was diagnosed with Hashimoto’s disease after a show in New York earlier this year (16). The condition prompts the immune system to attack the thyroid.

"People don’t realise how important the thyroid is," Jax said. "It’s more important than the actual brain. It was messing me up emotionally, putting me in a strange place.

"I was going through a lot, travelling a lot, living out of a suitcase. But I was waking up tired a lot, losing my voice and (I was) just kind of depressed and in a really dark place. My parents knew something was up."

And then she felt a lump in her throat and decided to get it checked out. Tests revealed 18 tumours on her thyroid, 12 of which were cancerous. They were all were successfully removed.

Despite her health setback, the singer is preparing to compete in the New York City Marathon in November (16) on behalf of the Tuesday’s Children charity.