Ovarian hormones at Higher Level: An AHL statement: two steroid hormones and what they do to their target cells.
Practise this as you read
- Outline the effects of oestradiol or progesterone.
- Identify the target cells of each.
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The big idea: Oestradiol and progesterone are steroid hormones made by the ovary. Both bind receptors inside their target cells and change gene expression. Oestradiol targets the hypothalamus cells that secrete GnRH: high levels before ovulation make them secrete more GnRH. Progesterone targets the endometrium, keeping it thick and ready for an embryo.
The points to remember
- Both are steroids: intracellular receptors, changes in gene expression.
- Oestradiol targets hypothalamus cells that secrete GnRH.
- High oestradiol, before ovulation: more GnRH, so more LH and FSH.
- Progesterone targets cells of the endometrium.
- It keeps the lining thick, with blood vessels; when it falls, the lining breaks down.
Remember it as: Oestradiol talks to the brain; progesterone keeps the lining.
Real example: support in IVF. After an embryo is placed in the uterus during IVF, women are usually given progesterone. It acts on the endometrium and keeps the lining ready, so the embryo can implant.
Trap: Only cells with the receptor respond: oestradiol and progesterone reach the whole body in the blood, but they change gene expression only in their target cells.
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How it is asked: Expect an MCQ on the target cells of each hormone, or an Outline question on the effects of oestradiol or progesterone on their target cells.
IB-style questionOutline[3 marks]
Outline the effects of progesterone on cells of the endometrium.
Model answer plan
See the answer broken into clear points, with guidance on how each point earns marks.