Texas Attorney General Ken Paxton sued a UT Southwestern associate professor and doctor for allegedly 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 Dr. 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 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 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, Children’s Health and Dr. Lau were not immediately available for comment.

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 laws was signed by Gov. Greg Abbott and it was 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 before the law went into effect on Sept. 1, 2023, that were to be filled or refilled after the enacted date.

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

Lau has been practicing as a 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 2001-04. She does not have any medical malpractice investigations on record, according to the state medical regulator’s website.

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.

DPS has asked Paxton for a written opinion on the legality of ignoring the court orders. That opinion has not yet been issued.