It is unlawful for a person not licensed under this chapter, or whose license has been suspended or revoked by the panel, to hold himself or herself out as a dietitian, licensed dietitian, alone or in combination, or use with the letters "LD" or any facsimile or combination in any words, letters, abbreviations, or insignia. An authorization to practice issued pursuant to this title is valid for up to two years and is renewable on dates as established by the director.