Question

a) Be able to identify and describe multiple factors involved in bone remodeling.

b)Describe the hormonal regulation of skeleton growth

Answer 1

Answer (a):

Multiple factors involved in bone remodeling:

Insulin-like growth factors I and II, transforming growth factor beta, fibroblast growth factor, platelet-derived growth factor, and bone morphogenetic proteins.

Insulin-like growth factors I and II: Insulin-like growth factor (IGF), formerly called somatomedin, any of several peptide hormones that function primarily to stimulate growth but that also possess some ability to decrease blood glucose levels.

Transforming growth factor beta: It is a polypeptide member of the transforming growth factor beta superfamily of cytokines. It is a secreted protein that performs many cellular functions, including the control of cell growth, cell proliferation, cell differentiation, and apoptosis.

Fibroblast growth factor: The fibroblast growth factors (FGF) are a family of cell signalling proteins that are involved in a wide variety of processes, most notably as crucial elements for normal development. Any irregularities in their function lead to a range of developmental defects.

Platelet-derived growth factor: PDGF plays a significant role in blood vessel formation, the growth of blood vessels from already-existing blood vessel tissue, mitogenesis, i.e. proliferation, of mesenchymal cells such as fibroblasts, osteoblasts, tenocytes, vascular smooth muscle cells and mesenchymal stem cells as well as chemotaxis.

Bone morphogenetic protein: Bone morphogenetic proteins are a group of growth factors also known as cytokines and as metabologens.

Answer (b):

The hormonal regulation of skeletal growth:

Several hormones are necessary for controlling bone growth and maintaining the bone matrix. The pituitary gland secretes growth hormone (GH), which, as its name implies, controls bone growth in several ways. It triggers chondrocyte proliferation in epiphyseal plates, resulting in the increasing length of long bones.

Along with these, three calcium-regulating hormones play an important role in producing healthy bone:

1) parathyroid hormone or PTH, which maintains the level of calcium and stimulates both resorption and formation of bone;

2) calcitriol, the hormone derived from vitamin D, which stimulates the intestines to absorb enough calcium and phosphorus and also affects bone directly; and

3) calcitonin, which inhibits bone breakdown and may protect against excessively high levels of calcium in the blood.