When the son of one of the consorts ascended the throne she became Valide Hatun (Mother of Sultan).
By the beginning of the 16th century, the title of sultan, carried by both men and women of the Ottoman dynasty, was replacing other titles by which prominent members of the imperial family had been known (notably hatun for women and bey for men), with imperial women carrying the title of "Sultan" after their given names.
This usage underlines the Ottoman conception of sovereign power as family prerogative.
[1] Towards the end of the seventeenth century the title hatun and sultan for imperial consorts was replaced by Kadın and Ikbal.
The title officially first came in use during the reign of Sultan Suleiman II.