Could some biomechanical effects of growth hormone help to explain its effects on bone formation and resorption?

This article suggests that growth hormone effects on bone biomechanical factors help to cause changes in osteoblastic and osteoclastic activities in gigantism and growth-hormone-deficiency states. The suggestion stands partly on the following evidence. (1) In growing mammals, acute partial disuse decreases or stops longitudinal bone growth and periosteal bone formation and increases in outside bone diameter, Yet, in metaphyseal spongiosa, bone resorption and formation continue and net bone losses usually increase. (2) The same pattern of findings occurs in very young rats 5 weeks after hypophysectomy, accompanied by cessation of body and muscle growth and also by reduced physical activity. (3) Another study reduced muscle forces on hindlimb bones by suspending rats by the tail, and found that supplemental growth hormone for 80 days increased hindlimb muscle mass but not hindlimb periosteal bone formation. (4) Such facts support the previous suggestion, which might supplement other ideas about this hormone's modes of action on bone physiology, They include the possibility that the hormone can modulate the responsiveness of bone's biologic mechanisms to mechanical and other nonmechanical influences. (C) 1998 by Elsevier Science Inc. All rights reserved.