Help needed with Homunculi!

[RaviStrife]

So....looking for a quick ruling on how hd scale on a iron defender homunculus. The original health calculation is a little strange, citing (2d10+10) despite no con. Also, there is a distinct lack of feats or anything else that would boost hp. Help?

[Yuki Akuma]

Look up the rules for Constructs. Notice the bonus HP. (http://www.d20srd.org/srd/typesSubtypes.htm#constructType)