What are hormones?

From Gina Clare

Hormones are long-range chemical messages used to send signals via the blood. They are produced by glands and they control all aspects of your biology, from growth and repair to metabolism and reproduction. Fat-soluble hormones like oestrogen and testosterone are made from fats like cholesterol. They go straight through the membrane of cells and into the nucleus, where they switch genes on and off. Water-soluble hormones like insulin and adrenaline are often made from short fragments of protein known as peptides. They can’t travel through cell membranes, so cells detect them using specialist receptors, which trigger cascades of signals to change cell behaviour.

Answered by Laura Mears for Brain Dump in How It Works issue 105

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