Growth factors are molecules which encourage or inhibit the multiplication of cells. They are protein substances which are often called “first messenger”. They enable multiplication and the inhibition of cells in the organism. Many growth factors are cytokines. Different types of growth factor can be distinguished according to the amount of amino acids (which form the basis of a protein) in them.

Growth factor primarily fixes itself onto a specific chemical molecule specific, called a “receptor”. This triggers its activation, which in turn results in another chemical molecule being produced, known as “second messenger”. This process in turn starts a chain of chemical reactions, the culmination of which is the synthesis of a protein known as a "regulatory protein". This has the capacity to accelerate or slow down phenomena. This protein binds to the genes which are involved in the division and differentiation of cells, thus altering their degree of activity. In this way, growth factors have the ability to encourage or limit, depending on the case, the synthesis of new tissue but also its growth and its repair when the organism suffers a lesion. (source: .vulgaris-medical)