1. Growth factors Polypeptides in nature
Work through cell surface receptors
Endocrine, paracrine or autocrine actions
Stimulation of cell proliferation (alone or in combination with other growth factors)

2. IGF-I ↑ GH, ↑ IGF-I or Somatomedin “C”
Plays role in cell cycle control, ↑cell growth (growth of bone and cartilage), and  apoptosis
Shares common properties with the insulin receptor and binds with lower affinity to the insulin receptor
 GH,  IGF-I
Acromegaly, ↑ IGF-I levels

3. IGF-I binding proteins
IGF-I Circulates in plasma with a large (MW 150,000) carrier proteins (at least six binding proteins have been isolated)
Very long plasma half life of IGF-I due to the binding proteins
Facilitators or inhibitors of IGF-I actions

4. IGF-II Involved in regulation of fetal growth
Receptor is quite different from the insulin and IGF-I receptor
Receptor is single polypeptide (identical to mannose-6-phosphate receptor) without any intrinsic phospho kinase activity

5. Epidermal growth factor (EGF):
The epidermal growth factor (EGF) family of polypeptides are regulators for tissue
development, proliferation, differentiation, survival (inhibitor of apoptosis) and repair of various cells.
EGF = urogastrone, a potent inhibitor of gastric acid secretion isolated from human urine.

6. Platelet - derived growth factor (PDGF):
Purified from platelet; present in serum (after clotting and platelet lysis) but not plasma.
Multifaceted inflammatory mediator secreted by fibroblasts, smooth muscle cells,
macrophages and endothelial cells.

7. Fibroblast growth factor (FGF):
Major biological role: stimulation of angiogenesis (capillary proliferation).

8. NGF (Nerve growth factor)
Purified from mouse salivary glands and snake venom
Promote growth, differentiation and survival of neurons

9. Erythropoietin
Regulates red blood cell proliferation
Made in kidney

10. Lymphocytes growth factors
Interleukins, thymosin
Activate lymphocytes proliferation and maturation
Important role in regulating immune response and inflammation

11. Growth factors and neoplasia
Normal Growth: Growth Stimulatory Factors = Growth Inhibitoy Factors
Development of Cancers by↑ in Growth Stimulatory Factors or  in Growth Inhibitory Factors

12. Transforming Growth Factors
TGF-α – Similar in structure to EGF and stimulates cell growth
TGF-β – Inhibits cell division