Major processes hormones control and integrate incl: reproduction, growth and development, maintenance of electrolyte, water, and nutrient balance of the blood, regulation of cellular metabolism and energy balance, mobilization of body defences. Scienti c study of hormones and endocrine organs called endocrinology. Hypothalamus has neural functions but also produces and releases hormones con- Pancreas, gonads (ovaries and testes), and placenta contains endocrine tissues. Hormones are long-distance chemical signals; autocrines and paracrines are short-dis- tance signals: autocrines chemicals exerting effects on same cells secreting them, paracrines acts locally but affects cell types other than those secreting them. Steroids: synthesized from cholesterol; only gonadal and adrenocortical hormones are steroids. Hormones in uence activity of target cells by altering cell activity. Hormones act at receptors in two different ways: mone) act on receptors in the plasma membrane: lipid-soluble hormones (steroid and thyroid hormones) act on receptors inside the cell, which directly activates genes.