Hormones and Metabolism

A single hormone, released from a gland the size of a pea at the base of your brain, can change how fast your heart beats, how much energy you feel, and how well you sleep, all without you noticing it happen. This lesson looks at how that messaging system works, and at the body's whole energy management system it helps run: metabolism.

A single hormone, released from a pea sized gland at the base of your brain, can change how fast your heart beats. It can also change how much energy you feel and how well you sleep, all without you noticing. This lesson looks at how that messaging system works, and at the body's whole energy management system it helps run: metabolism. Hormones: a slower, longer lasting kind of message Nerve signals are fast and specific, arriving in milliseconds and fading almost as quickly. Hormones work differently. They are chemical messages released by glands directly into the bloodstream, travelling wherever blood goes, and taken up only by the cells built to recognise them. A nerve signal is like a text message: instant, direct, brief. A hormone is more like a memo circulated round an entire building: slower to arrive, but read and acted on for as long as it takes effect. The main hormone producing glands Several glands, together called the endocrine glands, produce the hormones that keep this system running. The pituitary gland, no bigger than a pea and tucked beneath the brain, is often called the control gland, because many of its hormones tell other glands when to release their own. The thyroid gland, in the neck, sets the pace of metabolism: how quickly cells use energy and produce heat. The adrenal glands, sitting atop each kidney, drive the stress response and help regulate salt and fluid balance. The pancreas has a hormone releasing role alongside its digestive one, controlling blood sugar. The ovaries and testes produce the hormones behind reproduction and sexual development. Metabolism: the body's energy budget Metabolism is not just about body weight, even though that is usually the first thing people associate with the word. It is every chemical process that keeps you alive: breaking down food, releasing energy, building new tissue, storing fuel for later, and clearing away waste. Every organ, from the brain to the kidneys, depends on this constant chemistry. Blood sugar regulation shows hormones and metabolism working as one system. After a meal, hormones help move sugar from the blood into cells, and store some as reserve fuel. Between meals, other hormones release that stored fuel back into the blood, so energy supply keeps up even when you are not eating. Feedback loops: hormones correcting themselves Hormone systems mostly run on feedback loops, the same principle that keeps many of the body's internal conditions balanced. If a hormone level drifts too high or too low, the body adjusts the signal to bring it back toward a working range. This is why hormone problems often show up as a level being persistently too high or too low, rather than simply present or absent. What a doctor checks when this system is affected Hormone problems rarely announce themselves with one obvious sign, so a doctor builds a picture from several angles. Looking. Unexplained weight change, changes in skin or hair, unusual sweating, or a visible swelling in the neck can each point toward a specific gland. Growth and vital signs. Checking height, weight, heart rate, blood pressure and temperature can reveal patterns consistent with a hormone excess or deficiency, since several hormones directly affect all of these. Special tests. Blood tests measuring specific hormone levels are usually the most direct way to confirm a problem, often alongside a test of the gland that controls it. A hormone can be low for two reasons: the gland making it is underactive, or the gland further up the control chain is not sending a strong enough signal. When this system is affected When hormone levels drift outside their working range, people may notice fatigue, unexplained weight change, changes in mood or sleep, altered heart rate, or an intolerance to heat or cold. Because a single hormone can influence several organs at once, these symptoms often appear together in patterns rather than alone. These symptoms are explored further in the lessons "Persistent Tiredness and Fatigue" and "Unexplained Weight Loss".

Hormones are chemical messages released by glands into the blood, acting more slowly and for longer than nerve signals, and together with metabolism, the body's energy management chemistry, they help coordinate growth, energy, stress and reproduction.