Where does meta-data come from?

We are running into a strange problem -- one of our developers is
extracting meta-data from our data base, and is seeing a difference in
the data that is being returned.  Columns typed as int or int4 are
returning smallint from the meta-data information through jdbc, but if
we go in and look at the tables through \d in the command line client,
it is correctly typed as int.  This started happening after we upgraded
to 8.1.3 and after issuing alter table commands to create primary keys.
(one data base was fine after the upgrade -- yesterday, but today, after
creation of primary keys, is now giving us the wrong int type).

I'd like to know where jdbc is getting this information, so I can try to
track down the cause.

TIA.