IGCSE Biology glossary
Progesterone
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Definition
A hormone produced by the corpus luteum (in the ovary after ovulation) that maintains the thick, blood-rich lining of the uterus during the second half of the menstrual cycle. If an embryo implants, progesterone levels remain high to support pregnancy. If not, progesterone drops and menstruation begins.
What to include in an exam answer
Progesterone MAINTAINS the uterus lining; oestrogen REPAIRS and thickens it. This distinction is commonly tested. Progesterone inhibits further ovulation, which is why it is used in hormonal contraceptives.
Example in context
Explain the role of progesterone in the menstrual cycle (2 marks): Progesterone maintains the thickened lining of the uterus after ovulation. If the egg is not fertilised, progesterone levels fall and the lining breaks down, causing menstruation.
Related syllabus topic
Reproduction