Remember: some proteins are hormones and some hormones are proteins
What are proteins? See my blog post. Lots of proteins are NOT hormones, but some are.
What are hormones?
A hormone (from the Greek participle ὁρμῶν, “setting in motion”) is any member of a class of signaling molecules in multicellular organisms, that are transported to distant organs to regulate physiology and behavior. Hormones are needed for the correct development of both animals and plants. The definition of a hormone as a signaling molecule that acts far from its site of synthesis includes many different classes of molecules. Substances considered to be hormones include eicosanoids (a type of lipid, e.g. prostaglandins and thromboxanes), steroids (a type of lipid, e.g. estrogens and androgens), amino acid derivatives (e.g. epinephrine and melatonin), protein/polypeptides (e.g. insulin and melanocyte-stimulating hormone) and gases (nitrous oxide).
A growth factor is a naturally occurring substance capable of stimulating cell proliferation, wound healing, and occasionally cellular differentiation.
Growth factors typically act as signaling molecules between cells. Examples are cytokines and hormones that bind to specific receptors on the surface of their target cells. Growth factors are usually protein but some steroid sex hormones can act as growth factors. Growth factors are important for regulating a variety of cellular processes.