Updated at 3:45 p.m. with additional comments, including from Ted Cruz’s office.

AUSTIN — More than 2,000 parents and advocates say they oppose Sen. Ted Cruz’s comments calling a Dallas mother’s support for her child’s gender transition "abuse,” according to a letter from the Human Rights Campaign to the Texas Republican.

The letter states that Cruz’s remarks in response to the custody case of a Dallas 7-year-old who is a transgender girl, her mother says, are “harmful and medically unfounded.” It was posted earlier this week and signed by 2,014 people across the U.S., including at least 276 Texans as of Thursday evening. The letter was to be available to sign until Friday afternoon, said Nick Morrow, deputy communications director for the HRC.

“Your comments accusing parents of transgender and non-binary children of ‘child abuse’ betrays your office, your responsibilities and all sense of decency,” the letter states.

Cruz shared a story on Twitter alleging that the 7-year-old’s custody case could hinge on the child getting puberty blockers, calling it “horrifying and tragic.”

“For a parent to subject such a young child to life-altering hormone blockers to medically transition their sex is nothing less than child abuse,” he added.

The mother had sought mutual written consent from both parents before the child would undergo any gender medical procedures.

A 7-year-old child doesn't have the maturity to make profound decisions like this. The state of Texas should protect this child's right to choose—as an informed, mature person—and not be used as a pawn in a left-wing political agenda. #ProtectJamesYounger — Senator Ted Cruz (@SenTedCruz) October 24, 2019

The personal dispute between two divorced Coppell parents, who disagree on whether their child should transition from male to female, became national news and a GOP rallying point after Cruz and other Texas lawmakers promised they would intervene.

The case began when the child’s mother sought to modify a joint custody agreement if the father didn’t affirm the child’s social transition from male to female by allowing the child to wear girls’ clothing and go by a different name. Later, the child could decide to take medical steps such as puberty blockers, which temporarily pause puberty, with approval from a doctor.

The father began blogging a year ago that he feared his child would be “chemically castrated” by his ex-wife. In an October joint custody order, a Dallas judge noted that was never part of the order.

But Texas Gov. Greg Abbott, Lt. Gov. Dan Patrick and Attorney General Ken Paxton have all urged the state’s Child Protective Services department to look into the custody case. Several state representatives also vowed to outlaw children’s gender transition in the next legislative session.

The Human Rights Campaign decided to direct the letter to Cruz because of the “extreme nature of his comments” and his notoriety, Morrow said.

“Of all of the politicians who chose to target trans youth with their comments, Cruz has the largest national megaphone, and he used it to make one of the worst statements about transgender youth and their families,” he said.

A spokesman for Cruz said the letter is evidence that the left is using the child "to promote an ever-increasing radical agenda.”

“The discussion in this case hinges on whether it is appropriate to subject a seven-year-old child to life-altering hormone blockers to medically change their sex,” the spokesman said in a prepared statement.

The letter from the Human Rights Campaign also states that Cruz’s comments undercut the medical consensus, including guidance from the American Academy of Pediatrics, the American Psychiatric Association and the American Psychological Association. The groups say that allowing a transgender or nonbinary (neither female- nor male-identifying) child to express their gender identity can reduce risks of suicide.

The federal Centers for Disease Control has also confirmed that transgender youth face a “disproportionately higher risk” of suicide.

“As parents of transgender and non-binary children, we’ve become all too familiar with the danger that can come if a child is unable to express their deeply-held gender identity,” the letter states. “Every parent has their own journey, just as every child has their own — it is not always an easy one and it is made much more difficult when our families are exploited for political gain.”

Amber Briggle, the mother of an 11-year-old transgender boy in North Texas, said that Cruz is “no friend to the transgender community," and that his comments have helped put a target on other families with transgender children.

“If Ted Cruz and other lawmakers want kids to be older before we’re pumping them with hormones, you would think that these politicians would be in favor of puberty blockers because it buys them and their family more time to decide,” said Briggle, a member of the HRC’s Parents for Transgender Equality Council.

Blockers pause puberty without any permanent changes, according to the Mayo Clinic. Briggle also noted that it can be less painful and expensive for someone to transition if the person has not undergone puberty.

By Friday afternoon, an online petition to “save” the 7-year-old that was directed to Abbott, Cruz, Sen. John Cornyn and several Republican state senators had 245,248 of 300,000 needed signatures.

The petition, which appears to have been launched a year ago, states that it is “run from outside the US” and was not written or managed by the child’s father at any point.

“We the undersigned, demand that the Governor and Texas Legislature step in immediately to save [the child] and all other children under the threat of “social transitioning,” the petition states.

Briggle said the pushback against the 7-year-old’s mother from Texas Republicans such as Paxton, whom she invited to dinner at her house in 2016, has caused fear among families with transgender children that they could also be investigated or penalized by Texas’ protective services.

“If they can do that to one family, they can do that to any family,” she said. “We won’t stand for that.”

Briggle said she has a “safe folder," in which she is collecting proof of community and medical support for her child’s transition and is telling other parents to do the same. In it, she put a loving Mother’s Day letter from her son.

“These should be mementos. Not proof that I’m not a child abuser,” she said.