Noun
(countable) Initialism of police tactical unit.
(countable) Initialism of power transfer unit.
(uncountable) Initialism of paroxysmal tonic upgaze.
(uncountable) Abbreviation of propylthiouracil.
(uncountable) Abbreviation of phenylthiourea.
Source: en.wiktionary.orgThe most dangerous side effect is agranulocytosis (1/250, more in PTU). Source: Internet