Ph.D Thesis

Ph.D StudentDaher Ofra
SubjectThe Effect of Growth Hormone (GH) on Cartilage and Bone Loss
Following Prolonged Immobilization in Old Animals
DepartmentDepartment of Medicine
Supervisors MRS Erella Livne (Deceased)
ASSOCIATE PROF. Abraham Reznick


Age associated bone loss is the major cause underlying osteoporotic fractures in the elderly. Immobilization, additional factor leading to excessive bone loss and enhanced osteoporosis.

Purpose of the present study was to test whether supplementation of growth hormone       (GH) to immobilized aged rats will prevent or slow excessive bone loss.

Hind legs of 25-month-old female rats were casted for four weeks. Recombinant rat GH was injected every 3 days and tibiae, femurs, and lumbar vertebrae were collected for the various determinations.

Effects of GH  and immobilization varied  according to the type of bone tested (compact vs. spongy) , the location and loading mecahnics  (femur vs. tibia) and age (young v.s old). Changes in contralateral leg were more pronounced compared to immobilized leg, resulting from extra load imposed on it. GH reduced acid phospatase (ACP) activity and increased trabecular bone volume (%TBV) with possible implication on reduced bone osteoporosis and uncoupling of  bone formation/resorption process. GH reduced adipose tissue and increased growth plate dimensions in immobilized leg.  GH treatment caused significant increase in TBV, and IGF-I serum levels that were more pronounced in old animals. IGF-I levels were higher in young compared to old animals and IGF-I was localized mainly in the cartilage.

It is concluded that treatment with GH in old age reduced ACP and increased %TBV and IGF -I levels, features that may prevent excessive bone loss in aging.