The world's bestselling medical textbook removed the definition of gender dysphoria from its website after the Florida Department of Health cited it in recent guidance advising against gender transitions for children and adolescents, according to an email obtained by Fox News Digital.

The email from Melissa Adams, who is Merck Manuals' director of marketing and brand awareness, also asked the Florida Department of Health to adjust their guidance based on the update in the manual, which was first published in 1899 and remains the oldest continuously published medical textbook in English.

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"Gender dysphoria is characterized by a strong, persistent cross-gender identification associated with anxiety, depression, irritability, and often a wish to live as a gender different from the one associated with the sex assigned at birth," according to the Merck Manual's prior definition, which has since been removed.

Florida Surgeon General Joseph Ladapo speaks during a press conference at Neo City Academy in Kissimmee, Florida in September 2021.

Florida Surgeon General Joseph Ladapo speaks during a press conference at Neo City Academy in Kissimmee, Florida in September 2021. (Paul Hennessy/SOPA Images/LightRocket via Getty Images)

"We were in the process of updating our online chapter on that subject so I wanted to make sure you had the latest information," wrote Adams, who did not respond to multiple requests for comment.

"Some of the verbiage you reference in quotes has now been omitted as a result of the update which went live on our site at the end of April," Adams added.

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The email went on to request that Florida remove its language following their update. Florida Surgeon General Joseph Ladapo responded by tweeting a screenshot of Adams' email and alleging that Merck's move was "political activism disguised as medical advancement."

"Medicine cannot be a weapon used to divide communities, and Florida’s guidance will not change due to political pressure," Ladapo added.

Merck removed the definition from its website after Ladapo released a fact sheet on April 20 in response to guidelines from the Department of Health and Human Services (HHS) in March.

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According to the new guidance from HHS, "gender-affirming care" includes social affirmation at any age, puberty blockers during puberty and hormone therapy starting during early adolescence. Irreversible surgery is "typically used in adulthood or case-by-case basis in adolescence."

Assistant Secretary of Health and Human Services Rachel Levine testifies before the Senate Health, Education, Labor, and Pensions Committee on Feb. 25, 2021, on Capitol Hill in Washington, D.C.

Assistant Secretary of Health and Human Services Rachel Levine testifies before the Senate Health, Education, Labor, and Pensions Committee on Feb. 25, 2021, on Capitol Hill in Washington, D.C. (Tom Brenner-Pool/Getty Images)

Citing a "lack of conclusive evidence, and the potential for long-term, irreversible effects," the Florida Department of Health advised against social transition, puberty blockers, hormones and surgery as treatment options for children and adolescents.

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Ladapo's office told Fox News Digital that they are not planning on changing their guidance at this time.