"You said that you’re a trans woman?" McKee asked Herzig. "Do you have a penis?"
McKee's question riled some attendees, including one person who yelled out in the middle of the hearing, "Disgraceful."
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Herzig replied that McKee's question was "horrible."
"I don't know what my rights are, but that question was highly inappropriate," said Herzig, who has a doctorate in pharmacy.
"I'm a health care professional, a doctor," Herzig continued. "Please treat me as such. Next question, please."
Speaking later to NBC News, Herzig said she was expecting any other question "than what I got."
"It was probably the most publicly humiliating thing I've ever gone through," she told the outlet.
Republican Arkansas state Sen. Matt McKee drew audible gasps during a Senate Judiciary Committee hearing when he asked a transgender pharmacist about genitalia. (Arkansas State Senate)
Herzig acknowledged that video of the exchange was going viral, adding, "I really just hope it just shows people that there's people like me who want to stand up and that there are people who want to make sure there are access to resources."
McKee did not respond to Fox News Digital's request for comment.
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The Democratic Party of Arkansas later blasted McKee for his line of questioning, tweeting, "Republicans are not hiding their transphobia."
The heated exchange came during a hearing on a bill introduced in the Arkansas State Senate this month that would prohibit physicians from performing transgender surgeries or prescribing puberty blockers and cross-sex hormones to minors.
The proposed legislation would also allow people who have received such medical care to sue medical practitioners for up to 30 years after turning 18.
The bill passed through Arkansas' Senate Judiciary Committee on Monday.