Lara Pitt had no idea she had a serious disease until a troll pointed it out.

When Lara Pitt told doctors she was experiencing extreme fatigue, the Fox Sports presenter was turned away, and told it was nothing more than the stress of being a new mum.

Now, writing for Body & Soul, the 35-year-old has opened up about the hidden illness that arose after the birth of her first son, Lachlan. The disease which was only brought to her attention by, well… a troll.

“Sometimes Twitter can be a cold, harsh place. Other times it can unlock the mystery around a nagging health problem,” the mum-of-two wrote.

“Yep, I owe one helpful tweeter for pointing out – I didn’t have post-natal anxiety or depression, but in fact another post-partum health issue, commonly misdiagnosed.”

The NRL commentator’s symptoms included a heightened heart rate, restless sleeps, fatigue, breathlessness and excess sweating. Then, one day after work, a peculiar tweet caught her eye.

“Does Lara Pitt have an Adams Apple?” it read. Within days, she had noticed “a visible lump was sticking out of my neck, in a sort of heart-like-shape.”

“Some blood tests and an ultrasound revealed I was suffering post-partum Thyroiditis – a condition which occurs in 7-8 per cent of women approximately one to four months after delivery,” Lara said.

In layman's terms, when the thyroid gland produces too much or too little of the thyroid hormone, thyroiditis occurs. For months, Lara was "swinging" between too much (hyperthyroidism) and too little (hypothyroidism).

"For a few months I’d be depressed, lethargic, and not produce enough breast milk. Then I’d go the other way - feel anxious, have an increased heart-rate, go through rapid weight loss and poor sleep," she wrote.

With help from her husband, an endocrinologist, an osteopath, a refreshed exercise regime and nutrition plan, Lara managed to tackle the condition head on and made a full recovery.

LISTEN: Bec Judd and Monique Bowley discuss month four of having a baby. (Post continues...)

The popular sport personality is now concerned other mothers - who may be suffering post-partum mental health problems - are "getting misdiagnosed or not diagnosed at all."

"If you have a feeling something isn’t quite right, a simple blood test can set things straight," she urges women.

Have you been misdiagnosed post-partum? Share your stories with us below...