Examples of steroid hormones include the sex hormones estradiol and testosterone as well as the stress hormone cortisol. Steroid hormones РІР‚вЂњ these are made from cholesterol.They are grouped by the chemicals from which they are made. There are four types of hormones in most vertebrates. Hormones released by one gland can also tell other glands to make different hormones.

Homeostasis means to keep a constant state inside the body like temperature, amount of water and salts, and amount of sugar. Hormones help keep homeostasis in an organism. For example, the hormones estrogen and progesterone make girls go through puberty. Hormones also start and control sexual development. Hormones cause the growth and death of cells and of whole organisms. Metabolism is the chemical and energy reactions that happen in a living thing. The word 'hormone' was first used in 1905. The first discovery of a hormone was made in 1902. Sweat glands and salivary glands are examples of exocrine glands whose products are released outside the body. Some hormones are produced by exocrine glands, and some exocrine secretions release outside the body. The opposite word is 'exocrine', which means secreting through a duct or tube. Most internal secretions are from endocrine glands.

'Endocrine' means secreting directly into the blood. Glands are groups of cells that make something and release it (put it outside the cell). When many of these cells are together, they are called a gland. There are some cells whose main job is to make hormones. Many different kinds of cells can send a message. Hormones only act on cells which have the right receptors. The cell or tissue that gets the message is called the 'target'. When a hormone attaches to the receptor protein a mechanism for signalling is started. The cells which react to a given hormone have special receptors for that hormone. Every multicellular organism has hormones. Hormones are the signals which adjust the body's internal working, together with the nervous system. Hormones are the chemical messengers of the endocrine system. The chemical structure of the hormone Epinephrine (adrenaline)