Karnatakabhashabhushana 5.4

At the end of adu, idu, and udu, [there are] v and t in the masculine.

When the masculine gender is intended to be expressed, the phonemes v and t occur at the end of these specific stems adu, idu, and udu when any case inflection follows:

avaṁ [‘that man’],

ivaṁ [‘this man’],

uvaṁ [‘that intermediate man’],

ātaṁ [‘that man’],

ītaṁ [‘this man’],

ūtaṁ [‘that intermediate man’].

Before [a case inflection] beginning with a vowel, the augment n occurs in the masculine:

avanaṁ [‘that man (acc.)’],

ivanaṁ [‘this man (acc.)’],

uvanaṁ [‘that intermediate man (acc.)’],

atanaṁ [‘that man (acc.)’],

ītanaṁ [‘this man (acc.)’],

ūtanaṁ [‘that intermediate man (acc.)’].

Thus in all cases.