DO $$
DECLARE
r RECORD;
BEGIN
FOR r IN (SELECT table_name, column_name FROM information_schema.columns WHERE table_schema = 'public' AND table_name = 'your_table_name' AND column_name <> lower(column_name))
LOOP
EXECUTE format('ALTER TABLE %I RENAME COLUMN %I TO %I', r.table_name, r.column_name, lower(r.column_name));
END LOOP;
END $$;