Endocrinology (from Greek ἔνδον, endo, "within"; κρῑνω, krīnō, "to separate"; and -λογία, -logia, "the study of") is a branch of biology and medicine dealing with the endocrine system, its diseases, and its specific secretions called hormones, the integration of developmental events proliferation, growth, and differentiation (including histogenesis and organogenesis) and the coordination ofmetabolism, respiration, excretion, movement, reproduction, and sensory perception depend on chemical cues, substances synthesized and secreted by specialized cells.