I made a proposal for the importance of adjusting hit points for very large monsters based upon the unlikelihood of killing very large beasts by ordinary weapons. Earlier posts on the subject can be read here and here.
Below is a table that expresses a creature's total number of hit points based upon their mass, also known as biological units, or BU. See Hit Points. The total hit points/BU for creatures is based upon their weight, or mass. Thus, a goblin with typically 1 HD, weighing anywhere from 31 to 70 lbs, would have 1-4 hit points. A goblin of a tougher, hardier race, with a natural 2 HD, may have the same approximate body weight but more overall hit points: 2 x 1-4 hit points, or 2d4.