Hormones are chemicals, which are involved in the long-term control of a variety of processes in the body.

They are secreted by special glands directly into the bloodstream and transported around the body. 

Hormones only affect their specific target organ.

The concentration of glucose in the blood is monitored and controlled by the pancreas.

If the blood glucose concentration is high, the pancreas secretes insulin, which causes, the liver to absorb glucose and convert it to glycogen for storage, so lowering the level in the blood.

If the glucose concentration is too low, the pancreas secretes glucagons, which cause the liver to convert glycogen back into glucose and release it into the blood.

Diabetes is a disease in which the pancreas does not produce enough insulin.

If untreated, the blood glucose concentration could rise to a fatally high level.

Diabetics have to have regular injections of insulin to control the amount of glucose in their blood.

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Menstrual Cycle

A woman’s menstrual cycle is 28 days long.

Day 1 of the cycle is the first day of a period (menstruation). A period lasts about five days.  After this time, the uterus lining builds up again to prepare for pregnancy.

On about day 14, an egg is released from an ovary. This is called ovulation.

Several hormones are involved in the control of the menstrual cycle.

The oral contraceptive pill contains oestrogen that inhibits FSH production, so no eggs mature and the woman cannot become pregnant. However, there can be side effects. It can cause an increase in blood pressure and weight, and increase the risk of blood clots and some cancers. If the woman forgets to take a pill one day, it may not work and she could become pregnant.

Women who want to become pregnant, but who don’t ovulate regularly, can be given fertility drugs. These contain FSH that stimulates eggs to mature. 

One problem with these is that they can lead to multiple births if several eggs are released and fertilised.