Update value to "the first character is capital and the rest is small"

Hello all,

Does anyone have available plpgsql codes to update all capital letters
in a column to "the first character is capital and the rest is small" ?

For example, in tableA(id, description)
001,  'ZHANG ZHE XIN'                                              =>
'Zhang Zhe Xin'
002,  'LIU, WEI-HUAI'
=>    'Liu, Wei-Huai'
003,  'GU & WEI. NAN (CE SHI) & TOMMORROW'      =>   'Gu & Wei. Nan (Ce
Shi) & Tommorrow'

Thanks a lot!
Ying