Pictures always help! By "enclosed" I am guessing you mean it penetrates the 2x4. The alternative would be 2x4 wood on all sides. (Probably not)
The "post" may be cast iron and could be a drain pipe from upstairs plumbing . . . when you encounter these in the wall upstairs, it could be a vent pipe which allows air to get behind the draining water so it flows smoothly.
You can tell it is structural or not by looking for a flange which is nailed to the framing at the top or bottom. No flange means it is probably plumbing. You can get a clue if it is plumbing because there are connections (bell) or cleanouts at the bottom. The cleanout allows you to snake the line when it gets blocked.
These are educated guesses. Send pics and you will start getting really good advice . . .
Lastly, DO NOT remove this "post" until you are sure what it is.
Waiting to hear from you.