Adrenaline, insulin and the sex hormones

Structure and functions in living organisms · Hormones and temperature control · note 2 of 4

Spec 2.94Download all Hormones and temperature control notes (PDF)Download all notes (PDF)6 pages

Adrenaline, insulin and the sex hormonesSpec 2.94

In short

Hormones are chemicals secreted by glands into the blood. Adrenaline from the adrenal glands prepares the body for fight or flight by increasing heart rate. Insulin from the pancreas lowers blood glucose by making cells take up glucose and the liver store it as glycogen. Testosterone comes from the testes, and oestrogen and progesterone from the ovaries.

You need to know the source, role and effects of five hormones.

Five hormones: source, role and effects
Hormone	Source	Role and effects
Adrenaline	Adrenal glands (on top of the kidneys)	Prepares the body for fight or flight. Increases heart rate, so more blood (with oxygen and glucose) reaches the muscles for respiration. Stimulates the liver to change glycogen into glucose, raising blood glucose
Insulin	Pancreas	Controls blood glucose concentration. When blood glucose is high, the pancreas secretes insulin. Insulin makes cells take up glucose from the blood and makes the liver convert glucose into glycogen for storage, so blood glucose falls
Testosterone	Testes	Main male sex hormone. Controls the development of male secondary sexual characteristics at puberty and stimulates sperm production
Oestrogen	Ovaries	Main female sex hormone. Controls the development of female secondary sexual characteristics at puberty and helps repair and build up the uterus lining in the menstrual cycle
Progesterone	Ovaries	Maintains the lining of the uterus in the second half of the menstrual cycle and during pregnancy

Common mistake:

The pancreas makes insulin, but the liver stores glycogen. Do not write that the pancreas stores glucose.

Female and male body outlines showing the pancreas (insulin), the adrenal glands on top of the kidneys (adrenaline), the ovaries (oestrogen and progesterone) and the testes (testosterone). — Where the five hormones are made: **adrenal glands**, **pancreas**, **ovaries** and **testes**.

Written and checked against the Edexcel IGCSE Biology (4BI1) specification · Updated October 2026

Frequently asked questions

Why are hormones called chemical messengers?

Hormones are called chemical messengers because they are chemicals secreted by glands directly into the blood, which carries them to target organs where they cause an effect. Hormonal communication is slower than nervous communication, which uses electrical impulses, but its effects last longer. Hormones reach every part of the body but only affect their target organs.

What does insulin do to blood sugar?

Insulin lowers blood glucose concentration. When blood glucose is high, the pancreas secretes insulin into the blood. Insulin makes cells take up glucose from the blood and makes the liver convert glucose into glycogen for storage, so the blood glucose concentration falls. The pancreas makes insulin, but the liver stores the glycogen.

What does adrenaline do to the body?

Adrenaline prepares the body for fight or flight. It is released by the adrenal glands when a person is frightened or excited. It increases heart rate, so more blood carrying oxygen and glucose reaches the muscles for respiration. It also stimulates the liver to change glycogen into glucose, raising blood glucose.

All 5 questions on Hormones and temperature control