2.10.13Structure & Functions in Living Organisms
The Role of Hormones: ADH, FSH and LH — Edexcel International GCSE Biology 4BI1 Revision Notes & Topical Questions
5 min read 4 parts Lesson 11 of 21 Unit quiz
Part 1 of 4Three Pituitary Hormones
All three hormones are released into the blood by the pituitary gland at the base of the brain, then act on a distant target organ.
ADH
- Antidiuretic hormone makes the collecting ducts of the kidney nephrons more permeable to water, so more water is reabsorbed into the blood.
FSH
- Follicle-stimulating hormone causes an egg to begin maturing inside a follicle in the ovary and stimulates the ovary to release oestrogen.
LH
- Luteinising hormone triggers ovulation, the release of a mature egg, and stimulates the ovary to produce progesterone afterwards.
Pituitary gland
- This small endocrine gland releases the three hormones in response to signals from the hypothalamus and from other hormones in the blood.
| Hormone | Source | Target | Main effect |
|---|---|---|---|
| ADH | Pituitary gland | Kidney collecting ducts | Increases water reabsorption |
| FSH | Pituitary gland | Ovary | Egg maturation; oestrogen release |
| LH | Pituitary gland | Ovary | Ovulation; progesterone release |
Part 2 of 4ADH and Water Balance
Water content of the blood is kept steady by negative feedback involving ADH.
1
Osmoreceptors in the hypothalamus detect the concentration of solutes in the blood, which reflects how much water the blood contains.
2
If the blood has too little water, the pituitary gland releases more ADH into the bloodstream.
3
ADH makes the collecting ducts more permeable to water, so more water is reabsorbed by osmosis and a small volume of concentrated urine is produced.
4
If the blood has too much water, less ADH is released, the collecting ducts become less permeable, and a large volume of dilute urine is produced.
5
The return of blood water content to normal reduces the stimulus, which is the negative feedback that keeps the level stable.
Part 3 of 4FSH and LH in the Menstrual Cycle
Four hormones work togetherFSH and LH from the pituitary, and oestrogen and progesterone from the ovary.
FSH and LH in the Menstrual Cycle
FSH rises early
- At the start of the cycle FSH causes a follicle to develop and mature an egg, and the growing follicle secretes oestrogen.
Oestrogen
- Oestrogen repairs and thickens the uterus lining, and once its level peaks it stimulates the pituitary to release a surge of LH.
LH surge
- The sharp rise in LH causes ovulation, usually around the middle of the cycle, when the mature egg leaves the ovary.
Progesterone
- After ovulation the empty follicle becomes the corpus luteum, which secretes progesterone to maintain the thick uterus lining.
End of cycle
- If no embryo implants, progesterone falls, the lining breaks down and menstruation begins a new cycle.
Part 4 of 4Exam Checklist & Tips
2.10.13 – Key Points for the Exam
- ADH A hormone from the pituitary gland that increases the permeability of the collecting ducts to water.
- Osmoreceptor A cell in the hypothalamus that detects the solute concentration of the blood.
- Ovulation The release of a mature egg from the ovary, triggered by a surge of LH.
- Corpus luteum The structure left in the ovary after ovulation that secretes progesterone.
- Negative feedback A control system in which a change triggers a response that reverses the change.
Common Mistakes
- Saying ADH is made in the kidney; it is released by the pituitary gland and acts on the kidney.
- Writing that more ADH produces more urine; more ADH produces less, more concentrated urine.
- Mixing up FSH and LH; FSH matures the egg, whereas LH triggers its release.
- Stating that oestrogen and progesterone come from the pituitary gland; they come from the ovary.
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