Why do hormone receptors arise? An introduction.- The evolution of recognition.- Signal receivers and signal molecules.- Interrelation of hormone receptor evolution.- Conclusions.- Mechanisms of receptor-mediated transmembrane signaling.- Receptors, acceptors channels and the problem of transmembrane-signaling.- General mechanisms of transmembrane signaling.- Receptor dynamics and transmembrane signaling.- Receptor microclustering and cell activation.- Internalized receptor and cell activation.- Summary.- Insulin receptors: structure and function.- The molecular mechanism of insulin action.- The insulin receptor kinase.- Biochemical properties of the insulin receptor kinase.- Role of receptor phosphorylation in insulin action.- Structure-function relationship of the insulin receptor kinase.- Summary and conclusions.- Internalization of polypeptide hormones and receptor recycling.- Historical perspective.- Events at the cell surface (steps 1, 2 and 3).- Initial steps of endocytosis (steps 4 and 5).- Later steps of endocytosis (steps 6, 7 and 8).- Receptor recycling.- What determines the specificity of receptor-mediated endocytosis.- Biochemical features of receptor-mediated endocytosis.- Functional implications of receptor-mediated endocytosis.- Conclusions.- The nature and development of steroid hormone receptors.- Models of steroid hormone action.- Nuclear binding sites.- Development of steroid receptors: Ontogeny of estrogen receptors.- Receptor ontogeny and hormonal imprinting.- Receptor alterations during ontogenetic development.- Why is receptor adaptation necessary? An approach based on information theory.- Experimental evidence for hormonal imprinting.- Polypeptide hormones.- Imprinting by related hormones; the disturbing effect of ’noise’.- Overlapping imprinting by steroid hormones.- Imprinting with acid type hormones.- The importance and sensitivity of imprinting.- Hormonal imprinting in cell lines.- Cell-cell transmission of hormonal imprinting.- Hormonal imprinting at enzyme level.- The mechanism of imprinting.- The four stages of the development of encoded adaptation-requiring dynamic systems in mammals.- Medicinal aspects of hormonal imprinting.- The spectal case of hormonal imprinting, the neonatal influence of sex.- Historical perspectives.- Environmental influences on sexual differentiation.- Genetic influences on sexual differentiation.- Hormonal influences on sexual differentiation.- 1. Differentiation of the gonads.- 2. Differentiation of reproductive tract and external genitalia.- 3. Differentiation of the brain.- Conclusions.- The mechanism of receptor development as implied by hormonal imprinting studies on unicellular organisms.- The role of the cell membrane in hormonal imprinting.- The role of second messengers in hormonal imprinting.- Impact of the inhibition of endocytosis, transcription and translation on hormonal imprinting.- Impact of hormone concentration and time factor on hormonal imprinting.- Which materials can induce imprinting.- Study of induced receptors in the Tetrahymena.- Receptor ’memory’ in unicellular model systems.- Structural studies on membrane receptors of Tetrahymena.- Specificity of the hormone receptors of Tetrahymena.- The phylogeny of the endocrine system.- The scope of phylogeny.- Thyroidal phylogenesis.- The steroid ring system.- Peptide hormones.- Pathways of endocrine diversification.- Multiple sites and actions.- Invertebrates.- Challenging perspectives.- A new approach to the molecular evolution of hormones: the receptorial aspect.- The signal molecule potential of amino acids.- The signal molecule potential of oligopeptides.- Common origin and phylogenetic diversification of animal hormonal systems.- The significance of the evolutionary history of hormones.- The approach of comparative physiology.- The common base of intercellular messenger substances in multicellular organisms.- The different evolutions of animal and plant hormonal systems.- Diversification of hormonal systems in multicellular animals.- The evolutionary history of neurosecretion.- Neuroendocrine and epithelial endocrine glands.- Under what conditions do complicated hormonal systems evolve?.- Hormonal control of sexual differentiation.- The evolution of endocrine organs from the target tissue.- The principle of polytropic action.- Summary.- Receptors for intercellular messenger molecules in microbes: similarities to vertebrate receptors and possible implications for diseases in man.- Unicellular eukaryotes.- Prokaryotes.- Conclusion.- Development of hormone receptors: Conclusions.- Vertebrate hormones exist in invertebrates, in unicellular organisms and in plants.- Lower organisms possess receptors for vertebrate hormones.- Evolutionary aspects of hormones and receptors.- The genetic code for receptor synthesis.- Hormone-induced activation of receptor synthesis.- Hormone-induced organization of receptors.- A teleological point of view.