DALLAS >> Texas Attorney General Ken Paxton sued a UT Southwestern associate professor and physician on allegations of providing gender transition treatments to minors in the latest state action related to transgender issues.

Paxton filed suit Thursday in state court in Collin County against May C. Lau, who he says provided treatments to 21 minors in the form of “high-dose, cross-sex hormones and used false diagnoses and billing codes to mask the care.”

Lau practices adolescent and young adult medicine at UT Southwestern, a state school and medical research institution, as well as at Children’s Health in Dallas, which has a close affiliation with UTSW.

“Lau is a scofflaw who is putting the health and safety of minors at risk by prescribing testosterone, a controlled substance, to biological female minors for the purposes of transitioning their biological sex or affirming their belief that their gender identity is inconsistent with their biological sex in violation of Tex. Health Safety Code,” the lawsuit said.

The suit refers to Lau as a “Radical Gender Activist” and cites her treatment of gender dysphoria and study of gender-affirming care. Lau was also associated with the now-closed Gender Education and Care, Interdisciplinary Support (Genecis) program at UT Southwestern and Children’s Health.

UT Southwestern and Lau did not respond to requests for comment.

Children’s Health, in a statement, said it “follows and adheres to all state health care laws.”

“Our top priority is the health and well being of our patients,” Children’s Health said in the statement.

The Texas Legislature passed an aggressive ban on gender-affirming medical care for minors in 2023, making it illegal to “affirm the child’s perception of the child’s sex if that perception is inconsistent with the child’s biological sex.” The law was signed by Gov. Greg Abbott and upheld as constitutional by the Texas Supreme Court.

Paxton’s lawsuit listed 21 unnamed minors between ages 14 and 17 who were prescribed testosterone and other prescriptions used for “transitioning their biological sex or affirming their belief that their gender identity is inconsistent with their biological sex.”

The suit said Lau tried to circumvent the law by writing prescriptions to be filled or refilled before it went into effect on Sept. 1, 2023.

According to the suit, “each violation serves as an independent ground for revocation of Lau’s medical license.”

Lau has been a practicing physician in Texas since 2003, according to the Texas Medical Board. She graduated from Albany Medical College in New York state in 1998 and was a fellow at the Baylor College of Medicine Children’s Hospital in Houston from 2001 to 2004.

Earlier this year, the Department of Public Safety stopped making court-ordered changes to the sex listed on driver’s licenses for transgender Texans, and the Department of State Health Services stopped making similar changes to birth certificates.