Heather Rae El Moussa Diagnosed with Autoimmune Disorder After Believing Symptoms Were Due to 'Mom Brain'

Heather Rae El Moussa revealed that she was diagnosed with Hashimoto's disease, an autoimmune disorder she says was triggered by her pregnancy

Heather Rae El Moussa is opening up about the moment she was diagnosed with Hashimoto’s disease earlier this year.

The Selling Sunset alum, 36, recently spoke to Today about her health journey. The 36-year-old said she was four months postpartum when she started experiencing intense fatigue

“I remember saying to my assistant, ‘I feel like I’m dead,” she told the outlet. “My brain was so tired. My body was so tired. I was exhausted all the time and no amount of sleep could make it better.”

The real estate agent admitted that even being on camera for her show The Flipping El Moussas became draining. “Filming was absolutely brutal because I could barely get out of bed,” El Moussa added.

She initially believed that her symptoms were due to motherhood after welcoming her first child. El Moussa shares son Tristan, 9 months, with husband Tarek, 42, and is stepmom to his two kids, Brayden, 8, and Taylor, 13, whom he shares with ex-wife Christina Hall.

“I was like, ‘I’m probably just foggy because of mom brain,’” El Moussa recalled.

Related: What Is Hashimoto's Disease? Everything You Need to Know About Gigi Hadid's Thyroid Disorder

El Moussa didn’t think much of her symptoms until she noticed changes in her milk supply. After visiting a lactation consultant and getting blood work done, she was told that her pregnancy triggered Hashimoto’s disease.

Hashimoto’s disease is an autoimmune disorder where the immune system attacks the thyroid gland, accoridng to the National Institutes of Health. It causes symptoms like fatigue, weight gain, joint and muscle pain, slowed heart rate, dry skin, thinning hair and more.

"When she told me what I had, I was in total shock," said El Moussa, who learned the condition was also the cause of her depleted milk supply.

The reality TV star said she was prescribed medication for the autoimmune disorder and has since been “feeling much better.”

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Hashimoto’s is a common, manageable disease according to Dr. Terry Davies, a professor of medicine and director of the division of endocrinology at Mount Sinai Hospital in New York City.

“Hashimoto’s is inflammation of the thyroid gland, and it’s a very common disease,” he previously told PEOPLE. “It comes in mild and more severe forms, and it’s an autoimmune disease.”

“When the thyroid starts to fail — and the thyroid drives everything in the body, there’s nothing that doesn’t need the thyroid hormone — a low thyroid can lead to weight gain usually, can lead to depression, can lead to high cholesterol,” he explained. “It’s a very slow onset, and so when the patient comes to the doctor you’re never quite sure when the disease started. It could be a couple years ago, it could be quite recent, as opposed to other diseases where it’s quite sudden.”

In almost all cases, Hashimoto’s disease is incurable, but Davies said that the out-of-sync hormones are simple to control with a calibrated dose of thyroid replacement medicine.

“Treatment is very easy,” he said. “You just need to take it in the right dose, and the doctor can measure very, very precisely the right dosage.”

El Moussa is one of several celebrities  — including Gigi Hadid, Zoe Saldana, Gina Rodriguez and Victoria Justice — who have opened up about dealing with Hashimoto’s disease.

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