This code system http://hl7.org/fhir/gender-identity defines the following codes:

Code	Display	Definition
transgender-female	transgender female	the patient identifies as transgender male-to-female
transgender-male	transgender male	the patient identifies as transgender female-to-male
non-binary	non-binary	the patient identifies with neither/both female and male
male	male	the patient identifies as male
female	female	the patient identifies as female
other	other	other gender identity
non-disclose	does not wish to disclose	the patient does not wish to disclose his gender identity