I'm trying to figure out the difference between hormone, cytokine and protein hormone. It's clear to me that all three are biological messengers, but there seems to some ambiguity and overlap between terms and I'm trying to understand the nuances.
- What do each of these three terms mean and how are they different?
- Do any of the three terms represent a superset of the others? e.g are all cytokines, hormones? Are protein hormones just a subset of hormones?
- Are the terms context specific at all? For example, cytokines are referenced in the context of immunology below, but are they actually fundamentally different from hormones?
- If there is context-dependence, under which contexts should each word be used?
- Are there any canonical examples of each? e.g Prolactin is given as an example of a protein hormone below, how about for cytokines and ordinary hormones?
In June 1905, Ernest Starling, a professor of physiology at University College London, UK, first used the word 'hormone' in one of four Croonian Lectures—'On the chemical correlation of the functions of the body'—delivered at the Royal College of Physicians in London. Starling defined the word, derived from the Greek meaning 'to arouse or excite', as “the chemical messengers which speeding from cell to cell along the blood stream, may coordinate the activities and growth of different parts of the body” 
Cytokines and chemoattractant cytokines known as chemokines are highly localized soluble signaling proteins produced by many cells of the immune system (neutrophils, monocytes, macrophages, B-cells, and T-cells) to regulate immune responses 
A great deal of evidence has accumulated and confirmed that hormones secreted by the neuroendocrine system play an important role in communication and regulation of the cells of the immune system. Among protein hormones, this has been most clearly documented for prolactin (PRL), growth hormone (GH), and insulin-like growth factor-1 (IGF-I), but significant influences on immunity by thyroid stimulating hormone (TSH) have also been demonstrated. 
: Tata JR. One hundred years of hormones. EMBO Reports. 2005;6(6):490-496. doi:10.1038/sj.embor.7400444.
: Stenken JA, Poschenrieder AJ. Bioanalytical Chemistry of Cytokines-A Review. Analytica chimica acta. 2015;853:95-115. doi:10.1016/j.aca.2014.10.009.
: Kelley KW, Weigent DA, Kooijman R. Protein Hormones and Immunity. Brain, behavior, and immunity. 2007;21(4):384-392. doi:10.1016/j.bbi.2006.11.010.