POTS explained: The disorder that led OpenAI exec Fidji Simo to step down

• Fidij Simo is stepping down from her executive role at OpenAI.
• Simo took medical leave in April to treat postural tachycardia syndrome, or POTS.
• POTS is a disorder that can cause heart palpitations, lightheadedness, and fainting.

Fidji Simo is stepping down from her executive role at OpenAI.

Simo, the company's applications CEO, said she is leaving her full-time role due to her chronic illness in an X post on Thursday. She will transition to a part-time advisor.

Simo, who cofounded the Complex Disorders Alliance and the Metrodara Foundation, was diagnosed with postural tachycardia syndrome, or POTS, in 2019. She was initially misdiagnosed by doctors, including one who credited her health issues to being a "tired mom," Simo told Fortune in 2021.

This April, Simo took a temporary medical leave to treat the chronic illness.

"During that time, it became clear that the road to recovery would be much longer and more complex than I had anticipated — and that I needed to focus on it fully," Simo wrote on X. "When I went on leave, many people told me I was courageous for prioritizing my health. The truth is that I am only making this decision now because I failed to make it many times before."

Today, I shared with the OpenAI team that I have decided to leave my full-time role at OpenAI and transition to being a part-time advisor.

Three months ago, I had to go on medical leave after a severe exacerbation of a chronic illness I’ve lived with for seven years. During that…

— Fidji Simo (@fidjissimo) July 9, 2026

POTS affects the autonomic nervous system, which regulates involuntary functions such as blood pressure, heart rate, and respiration. The National Institute of Neurological Disorders and Stroke said people with POTS often have orthostatic intolerance, which is a set of symptoms that occur when a person stands up and are relieved by lying down.

"Symptoms of orthostatic intolerance, which often include dizziness or fainting, happen because not enough blood flows back to the heart when the person moves from a lying down or seated position to standing up," the agency said.

Through Simo's organizations, scientists are conducting research and trying to find cures for disorders like POTS.

Who is most likely to get POTS?

Although anyone can be diagnosed with POTS, the disorder mostly affects people between 15 and 50 years old. POTS is more common in women than in men.

"POTS commonly begins after a pregnancy, major surgery, puberty, trauma, or a viral illness. Some people report an increase in episodes of POTS right before their menstrual periods," the National Institutes of Health says.

People with a family history of POTS are at a "higher risk."

What are the symptoms of POTS?

A "classic" symptom of POTS is a fast heartbeat, but the disorder can also cause dizziness, lightheadedness, fainting, and heart palpitations that occur when standing up.

"Some people may have blurred vision or tunnel vision, weakness in the legs, chest pain or other pain, fatigue, sleep problems, digestive issues, shortness of breath, and difficulty concentrating," the NIH said.

Over time, POTS symptoms can improve, but some may remain or persist for a long time.

Why is POTS hard to diagnose?

The NIH says scientists aren't sure what exactly causes POTS.

"Doctors typically begin by reviewing a person's medical history and discussing their symptoms," the health agency says. "They may also measure heart rate and blood pressure and observe how the body responds to changes in position, such as standing up quickly."

How is POTS treated?

Treatment for POTS is focused on managing issues with blood flow and low blood volume.

Some medications can offer short-term relief, but scientists are still determining their long-term effectiveness. Lifestyle changes can help lessen symptoms, including increasing salt intake and staying hydrated.

How does COVID-19 impact POTS?

Some people with long-term COVID have developed POTS, but scientists are still determining why, according to the NIH.

People with POTS symptoms related to COVID-19 can also experience anxiety, depression, cognitive issues, brain fog, and sleep problems.