This case-sensitive code system http://hl7.org/fhir/pronouns defines the following codes:

Code	Display	Definition
he-him	He, Him, His, Himself	English pronouns typically associated with masculinity
she-her	She, Her, Hers, Herself	English pronouns typically associated with femininity
they-them	They, Them, Their, Theirs, Themself	English personal pronouns typically not associated with masculinity or femininity
other	Other	The individual uses pronouns other than he/him, she/her, or they/them
unknown	Unknown	No pronouns are known.