A professional group of American paediatricians has urged educators and lawmakers to reject policies that normalise chemical and surgical sex change operations.
"Facts – not ideology – determine reality," the American College of Pediatricians (ACP) said.
They warned that "conditioning children into believing that a lifetime of chemical and surgical impersonation of the opposite sex is normal and healthful is child abuse."
It will confuse children and parents, resulting to more children going to "gender clinics" where they will be given puberty-blocking drugs, the ACP said.
"This, in turn, virtually ensures that they will 'choose' a lifetime of carcinogenic and otherwise toxic cross-sex hormones, and likely consider unnecessary surgical mutilation of their healthy body parts as young adults," the physicians' group warned.
The norm for human design is either male or female, they said, and that sex development disorders (DSDs) like testicular feminisation and congenital adrenal hyperplasia are disorders.
"Individuals with DSDs do not constitute a third sex," the ACP said.
The group said no one is born with a gender but only biological sex.
"People who identify as 'feeling like the opposite sex' or 'somewhere in between' do not comprise a third sex. They remain biological men or biological women," the doctors explained.
When a person believes that he or she is the opposite sex is "a sign of confused thinking."
"When an otherwise healthy biological boy believes he is a girl, or an otherwise healthy biological girl believes she is a boy, an objective psychological problem exists that lies in the mind not the body, and it should be treated as such," the ACP recommended.
These people suffer from gender dysphoria, which is "a recognised mental disorder in the most recent edition of the Diagnostic and Statistical Manual of the American Psychiatric Association (DSM-V)."
The ACP warned that puberty-blocking hormones are dangerous as these can "inhibit growth and fertility in a previously biologically healthy child."
"According to the DSM-V, as many as 98 percent of gender confused boys and 88 percent of gender confused girls eventually accept their biological sex after naturally passing through puberty," the group said.
People who use cross-sex hormones and undergo sex change operations are 20 times more likely to commit suicide, it added.