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

Code	Display	Definition
non-binary	Non-binary	the individual identifies with neither/both female and male
male	Male	the individual identifies as male
female	Female	the individual identifies as female
other	Other	other gender identity
non-disclose	Does not wish to disclose	the individual does not wish to disclose their gender identity