North Carolina became the latest state to block minors from having access to gender-transition care, as Republican lawmakers voted on Wednesday to override the governor’s veto of a bill restricting hormone treatments, puberty blockers and surgeries for young people.

The move came as the State Legislature’s Republican supermajorities marshaled the votes to topple several other of Gov. Roy Cooper’s vetoes, reviving legislation that limits female transgender students’ participation in school sports and restricts what can be taught in schools about gender and sexual orientation.

North Carolina now joins about 20 other states that have enacted legislation blocking access to transition-related care for minors, with many of those laws passed this year as conservative lawmakers across the country have seized upon L.G.T.B.Q. issues.

Supporters of the measures have argued that they protect children from medical treatments they see as risky and unproven. On Wednesday, State Representative Hugh Blackwell, a Republican, said that the laws of North Carolina had long taken “extra steps to protect the interests of minors.”

“This legislation is in that same spirit,” he said, “recognizing the serious and the potentially permanent effects of the procedures that this bill addresses. It simply says that they need to wait until they are 18 to make that kind of decision.”

But critics have contended that denying access to this kind of care can be dangerous and detrimental to transgender youths, who have high rates of anxiety, depression and suicide attempts, and whose mental health could improve with gender-affirming care, some research has shown.

“You can say that this is not anti-L.G.B.T.Q., but it is,” Senator Lisa Grafstein, a Democrat, told other lawmakers during the debate on Wednesday. “What we’re doing here will hurt people.”

This month, the American Academy of Pediatrics reaffirmed its support of gender-related treatments for children, while also commissioning a systematic review of medical research on the treatments.

Mr. Cooper, a Democrat, has assailed Republicans for getting swept up in what he described as “political culture wars,” devoting their attention to targeting a small and marginalized group of young people instead of to more pressing issues confronting the state.

“North Carolina should continue to let parents and medical professionals make decisions about the best way to offer gender care for their children,” Mr. Cooper said in a statement issued after he had vetoed the ban on transition-related care in July.

Mr. Cooper also invoked the state’s history as the first to pass a bill, in 2016, that barred transgender people from using public restrooms consistent with their gender identity, a move that unleashed a firestorm of criticism and resulted in corporations’ scuttling expansion plans in the state and national sporting events’ being moved elsewhere.

Republicans in North Carolina secured their narrow supermajority in the State House of Representatives this year after Tricia Cotham, who had been elected as a Democrat from a district outside Charlotte, changed parties three months after she had taken office in January.

The switch outraged Democrats and was seen by some in her district as a betrayal. Yet the move empowered Republicans, who also have a supermajority in the Senate, to steamroll Mr. Cooper’s vetoes, including, most notably, his attempt to block a 12-week limit on most abortions, instituting the state’s most restrictive abortion policy in decades.

The bill on gender-transition care, House Bill 808, was passed by the State Legislature in June. The legislation bars medical professionals in the state from prescribing hormone therapy, puberty blockers or gender-transition surgery to anyone under the age of 18. Minors who had already began any of the treatments before Aug. 1 will be able to continue receiving treatment if their doctors deem it in their best interest and if they have parental consent, according to the legislation.

N.C. Values Coalition, a conservative group that supported the bill, praised lawmakers for making a “heroic decision” by overriding the veto.

But some lawmakers pleaded to their colleagues in personal terms to decide against adopting legislation they saw as unnecessary.

“As you consider this vote this afternoon, just stop it,” said State Representative John Autry, a Democrat, who has a granddaughter who is transgender. “You can stop it right here, right now, today.”