Hormones in human reproduction — AQA GCSE Biology
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Hormones in human reproduction explained
Reproduction in humans is controlled by hormones.
Read the full explanation
FSH, released by the pituitary gland, causes an egg to mature in an ovary and stimulates the ovaries to release oestrogen. Oestrogen, produced by the ovaries, causes the lining of the uterus to thicken and stimulates the release of LH. A surge of LH from the pituitary gland triggers ovulation, the release of a mature egg from the ovary. After ovulation, the remains of the follicle form the corpus luteum, which secretes progesterone. Progesterone maintains the lining of the uterus, ready for a fertilised egg to implant. If fertilisation does not occur, the corpus luteum breaks down, progesterone levels fall, and the lining is shed as menstruation. The cycle then begins again.
During puberty reproductive hormones cause secondary sex characteristics to develop.
Puberty is the stage of development when the reproductive system becomes mature. It is triggered by hormones released by the pituitary gland, which stimulate the testes in males and the ovaries in females. Testosterone, produced by the testes, causes secondary sex characteristics such as deepening of the voice, growth of facial and body hair, and increased muscle development. Oestrogen, produced by the ovaries, causes secondary sex characteristics such as breast development, widening of the hips, and the start of menstrual cycles. These changes prepare the body for reproduction. The hormones are carried in the blood to their target organs, where they produce specific effects.
Oestrogen is the main female reproductive hormone produced in the ovary.
Oestrogen is a steroid hormone and the principal female reproductive hormone. It is secreted by the ovaries, specifically by the developing follicle and the corpus luteum after ovulation. As a hormone, it travels in the bloodstream to target cells with complementary receptors, so it can act on distant tissues. Its roles include promoting female secondary sexual characteristics at puberty, such as breast development and widening of the hips, and regulating the menstrual cycle by stimulating thickening of the uterus lining and influencing the release of other hormones. For example, rising oestrogen concentrations in the first half of the cycle help trigger a surge in luteinising hormone that leads to ovulation. Understanding its ovarian source and main female role is essential before studying cycle control.
At puberty eggs begin to mature and one is released approximately every 28 days.
Puberty is the stage when reproductive hormones rise and the reproductive system becomes functional. In females, eggs already present in the ovaries begin to mature, and usually one egg is released about every 28 days. This cycle is controlled by hormones including follicle stimulating hormone, oestrogen, luteinising hormone and progesterone. The egg matures inside a follicle in the ovary; rising oestrogen from the follicle helps trigger a luteinising hormone surge, which causes the follicle to rupture and release the egg. The approximate 28-day timing is an average, and cycles can vary between individuals and from month to month. The released egg survives for roughly a day, so timing matters for fertilisation. This statement links puberty, egg maturation and the regular release that underpins the menstrual cycle.
This is called ovulation.
Ovulation is the release of a mature egg from a follicle in the ovary. It is the event referred to by the previous statement about an egg being released approximately every 28 days. Ovulation occurs around the middle of the menstrual cycle and is triggered by a surge in luteinising hormone from the pituitary gland. Before ovulation, follicle stimulating hormone stimulates a follicle to mature and oestrogen rises; the oestrogen peak helps cause the luteinising hormone surge. After the follicle ruptures, the egg is swept into the oviduct, where fertilisation may occur if sperm are present. The remains of the follicle become the corpus luteum, which secretes progesterone. Ovulation is therefore a key link between hormonal control and the possibility of fertilisation.
Testosterone is the main male reproductive hormone produced by the testes and it stimulates sperm production.
Testosterone is the principal male reproductive hormone. It is produced by the testes, specifically by the interstitial cells between the seminiferous tubules. As a hormone, it is carried in the bloodstream and acts on target cells with complementary receptors. Its main reproductive role is to stimulate sperm production in the testes, and it also promotes male secondary sexual characteristics at puberty, such as deepening of the voice, growth of facial and body hair, and increased muscle development. Sperm production occurs in the seminiferous tubules and is also supported by follicle stimulating hormone and luteinising hormone from the pituitary gland, but testosterone is the main male reproductive hormone named in the specification. This statement links the testes, testosterone and sperm production.
Several hormones are involved in the menstrual cycle of a woman.
The menstrual cycle is a recurring sequence of events in the female reproductive system, typically lasting about 28 days, that prepares the body for a possible pregnancy. It is controlled not by a single chemical but by several hormones acting in sequence and in feedback loops. The main hormones are follicle stimulating hormone (FSH), luteinising hormone (LH), oestrogen and progesterone. FSH and LH are secreted by the pituitary gland in the brain, while oestrogen and progesterone are secreted by the ovaries. Their changing concentrations coordinate two key events: the maturation and release of an egg, and the thickening and maintenance of the uterus lining. If no fertilised egg implants, hormone levels fall and the lining breaks down as menstruation. Understanding that multiple hormones interact, rather than one hormone acting alone, is essential before studying their individual roles.
Follicle stimulating hormone (FSH) causes maturation of an egg in the ovary. • Luteinising hormone (LH) stimulates the release of the egg. • Oestrogen and progesterone are involved in maintaining the uterus lining.
Each hormone in the menstrual cycle has a specific role. FSH, made by the pituitary gland, travels in the blood to the ovaries and causes an egg to mature inside a follicle. As the follicle develops, the ovary secretes oestrogen, which stimulates the uterus lining to thicken and repair after menstruation. When oestrogen reaches a high enough level, it triggers a surge of LH from the pituitary gland. LH stimulates ovulation, the release of the mature egg from the ovary. After ovulation, the remains of the follicle form the corpus luteum, which secretes progesterone. Progesterone maintains the thickened uterus lining so that a fertilised egg could implant. If fertilisation does not occur, the corpus luteum breaks down, progesterone and oestrogen levels fall, and the lining is shed during menstruation.
(HT only) Students should be able to explain the interactions of FSH, oestrogen, LH and progesterone, in the control of the menstrual cycle.
The menstrual cycle is controlled by a sequence of hormonal interactions involving negative and positive feedback. FSH from the pituitary gland stimulates an egg to mature and also stimulates the ovary to secrete oestrogen. Rising oestrogen thickens the uterus lining and, at high concentration, stimulates the pituitary gland to release a surge of LH. This LH surge triggers ovulation. After ovulation, the corpus luteum secretes progesterone, which maintains the uterus lining and inhibits FSH and LH release so that no further eggs mature during that cycle. If fertilisation does not occur, the corpus luteum degenerates, progesterone falls, and the pituitary can secrete FSH again, restarting the cycle. Explaining these interactions means linking each hormone to the next in a cause-and-effect chain and identifying where feedback inhibits or stimulates secretion.
(HT only) Students should be able to extract and interpret data from graphs showing hormone levels during the menstrual cycle.
Graphs of hormone levels during the menstrual cycle usually plot concentration on the vertical axis against time in days on the horizontal axis, with separate lines for FSH, LH, oestrogen and progesterone. To extract data, read values from the axes accurately, including peaks, troughs and the day on which each occurs. To interpret, link each feature to a biological event: the FSH peak early in the cycle corresponds to egg maturation; the oestrogen peak precedes the LH surge; the sharp LH peak coincides with ovulation around the middle of the cycle; and the progesterone peak in the second half maintains the uterus lining. A fall in progesterone and oestrogen near the end corresponds to menstruation. You may also be asked to compare curves, describe trends, or explain why one hormone rises or falls in relation to another.
Your focus
- Describe the roles of FSH, LH, oestrogen and progesterone in the menstrual cycle.
- Explain how changes in hormone concentrations bring about ovulation and menstruation.
- Sequence the main events of the menstrual cycle and link each to its controlling hormone.
Show all 30 objectives
- Describe the role of reproductive hormones in causing secondary sex characteristics during puberty.
- Identify named secondary sex characteristics in males and females.
- Explain how hormones travel in the blood to target organs to produce specific effects.
- Identify the ovary as the main source of oestrogen.
- Describe oestrogen as the main female reproductive hormone.
- Explain at least one reproductive function of oestrogen in the menstrual cycle or at puberty.
- Describe what happens to eggs at puberty.
- State the approximate interval between egg releases.
- Link egg maturation and release to hormonal control in the menstrual cycle.
- Define ovulation as the release of a mature egg from the ovary.
- Describe the hormonal trigger for ovulation.
- Place ovulation in the correct sequence within the menstrual cycle.
- Identify the testes as the source of testosterone.
- Describe testosterone as the main male reproductive hormone.
- Explain how testosterone stimulates sperm production and contributes to male secondary sexual characteristics.
- Name the four main hormones involved in the menstrual cycle and state where each is produced.
- Outline the main events of the menstrual cycle in the correct order.
- Explain that the cycle is controlled by the interaction of several hormones rather than one.
- Describe the role of FSH in maturing an egg.
- Describe the role of LH in stimulating ovulation.
- Explain how oestrogen and progesterone affect the uterus lining.
- Explain how FSH and oestrogen interact to control egg maturation and lining thickening.
- Explain how oestrogen and LH interact to trigger ovulation.
- Explain how progesterone provides negative feedback on FSH and LH to regulate the cycle.
- Extract accurate values for hormone concentration and time from a menstrual cycle graph.
- Interpret peaks and troughs by linking them to events such as ovulation and menstruation.
- Compare hormone curves to explain the sequence of hormonal control.
Hormones in human reproduction exam tips
Marking Points
- FSH is released by the pituitary gland and causes an egg to mature in the ovary.
- Oestrogen is produced by the ovaries and causes the lining of the uterus to thicken.
- LH is released by the pituitary gland and triggers ovulation.
- Progesterone is produced by the corpus luteum and maintains the lining of the uterus.
- If fertilisation does not occur, progesterone levels fall and the lining of the uterus is shed during menstruation.
- The hormones interact through feedback, so changes in one hormone affect the release of others.
- Puberty is triggered by hormones from the pituitary gland that stimulate the testes or ovaries.
- Testosterone is produced by the testes and causes male secondary sex characteristics.
- Oestrogen is produced by the ovaries and causes female secondary sex characteristics.
- Examples of male secondary sex characteristics include voice deepening, facial hair growth and increased muscle development.
- Examples of female secondary sex characteristics include breast development, widening of the hips and the start of menstrual cycles.
- The hormones travel in the blood to target organs, where they bring about the changes of puberty.
- States that oestrogen is a hormone, so it is a chemical messenger carried in the blood plasma to target cells.
- Identifies the ovary as the main site of oestrogen production in females.
- Names the ovary as the organ containing the follicles and corpus luteum that secrete oestrogen.
- Describes at least one reproductive role, such as promoting female secondary sexual characteristics at puberty.
- Explains that oestrogen helps regulate the menstrual cycle, including thickening of the uterus lining.
- Links oestrogen to the control of other reproductive hormones, such as its role in triggering the luteinising hormone surge before ovulation.
- States that puberty is the life stage when reproductive hormones become active and the reproductive system matures.
- Explains that eggs begin to mature in the ovaries at puberty.
- States that one egg is usually released approximately every 28 days.
- Names the follicle as the ovarian structure in which an egg matures.
- Links egg maturation and release to hormonal control, such as follicle stimulating hormone stimulating follicle growth and luteinising hormone triggering release.
- Recognises that 28 days is an average figure and that cycle length varies between individuals.
- Defines ovulation as the release of a mature egg from the ovary.
- Identifies the follicle as the structure from which the egg is released.
- States that ovulation occurs approximately midway through the menstrual cycle.
- Names luteinising hormone as the hormone that triggers ovulation.
- Describes the sequence in which follicle stimulating hormone matures the follicle and oestrogen helps trigger the luteinising hormone surge.
- Links ovulation to the formation of the corpus luteum and the later secretion of progesterone.
- States that testosterone is the main male reproductive hormone.
- Identifies the testes as the organ that produces testosterone.
- Explains that testosterone stimulates sperm production in the testes.
- Names the seminiferous tubules as the site of sperm production.
- Describes at least one additional role, such as promoting male secondary sexual characteristics at puberty.
- Recognises that testosterone travels in the blood to target cells, acting as a chemical messenger.
- Identify the pituitary gland as the source of FSH and LH, and the ovaries as the source of oestrogen and progesterone.
- State that the cycle is approximately 28 days long and involves coordinated changes in several hormones.
- Recognise that the cycle prepares the uterus lining for a possible pregnancy and that menstruation occurs if implantation does not happen.
- Describe the overall sequence: FSH matures an egg, oestrogen builds the lining, LH triggers ovulation, and progesterone maintains the lining.
- Explain that hormone concentrations change over time and that these changes are controlled by feedback between the pituitary gland and the ovaries.
- State that FSH causes an egg to mature in the ovary.
- State that LH stimulates the release of the egg, a process called ovulation.
- State that oestrogen is involved in repairing and thickening the uterus lining.
- State that progesterone maintains the uterus lining after ovulation.
- Link each hormone to its source: FSH and LH from the pituitary gland, oestrogen and progesterone from the ovaries.
- Explain that FSH stimulates the ovary to produce oestrogen as well as maturing the egg.
- Explain that high oestrogen levels stimulate an LH surge from the pituitary gland.
- Explain that LH triggers ovulation and the formation of the corpus luteum.
- Explain that progesterone from the corpus luteum maintains the uterus lining and inhibits FSH and LH secretion.
- Explain that falling progesterone when no fertilisation occurs allows FSH to rise and restart the cycle.
- Read values accurately from the axes, including the day and concentration of each peak.
- Identify the order of the peaks: FSH early, then oestrogen, then LH, then progesterone.
- Link the LH peak to ovulation at around the middle of the cycle.
- Link the progesterone peak to maintenance of the uterus lining after ovulation.
- Explain a fall in hormone concentration, such as progesterone falling before menstruation.
Examiner Tips
- 💡Name the gland or organ that releases each hormone when describing its role.
- 💡Sequence the events of the menstrual cycle in order, linking each hormone to its effect.
- 💡Use the terms ovulation, corpus luteum and menstruation accurately in written answers.
- 💡Give named examples of secondary sex characteristics for each sex rather than general statements.
- 💡Link each characteristic to the hormone that causes it.
- 💡Use the term target organ when explaining how hormones bring about specific effects.
- 💡Use the phrase main female reproductive hormone when defining oestrogen, because the specification distinguishes main roles from other hormones.
- 💡When asked where it is produced, write ovary rather than reproductive system, as the organ is the precise answer.
- 💡Link oestrogen to a named effect, such as uterus lining thickening or female secondary sexual characteristics, to show understanding rather than recall of a single word.
- 💡Use the word approximately when quoting 28 days, because the specification presents it as a typical interval rather than an exact value.
- 💡Name the ovary and the follicle when describing where maturation occurs, as vague answers about the reproductive system lose precision.
- 💡Connect the timing to hormonal control by mentioning follicle stimulating hormone or luteinising hormone where the question asks for an explanation.
- 💡Use the exact term ovulation when asked to name the release of an egg, as this is the specification term.
- 💡If asked to sequence events, place ovulation after follicle maturation and the oestrogen rise, and before corpus luteum formation.
- 💡Mention luteinising hormone when explaining the trigger, because naming the hormone shows cause rather than mere description.
- 💡Use the phrase main male reproductive hormone when defining testosterone, as the specification distinguishes main roles.
- 💡Name the testes precisely rather than writing male reproductive system, because the organ is the expected answer.
- 💡Link testosterone to sperm production and to one secondary sexual characteristic to show both reproductive and developmental roles.
- 💡Name the gland that secretes each hormone, as marks are often awarded for correct sources.
- 💡Use the terms maturation, ovulation and menstruation accurately rather than vague words such as 'release' for every event.
- 💡When asked to describe the cycle, work through the events in chronological order to show the sequence clearly.
- 💡Match each hormone to one clear job in a table or bullet list to avoid mixing up their roles.
- 💡Use the word ovulation when describing the release of the egg, as it is the precise scientific term.
- 💡Mention the uterus lining when discussing oestrogen and progesterone, since both are assessed in relation to it.
- 💡Use arrows or a flow diagram in your answer to make the sequence of interactions clear.
- 💡Name the gland or organ that responds at each step, such as the pituitary gland or ovary.
- 💡Include the word inhibits when describing how progesterone prevents further eggs maturing in the same cycle.
- 💡Quote specific days and values from the graph to support each point you make.
- 💡Use comparative language such as 'higher than' or 'peaks before' when describing two curves.
- 💡Check whether the question asks you to extract data, interpret it, or both, and answer accordingly.
Common Mistakes
- Confusing FSH and LH: FSH matures the egg, while LH triggers ovulation.
- Saying that oestrogen maintains the uterus lining: progesterone maintains it, while oestrogen thickens it.
- Thinking that progesterone is always high: it falls when the corpus luteum breaks down, causing menstruation.
- Confusing the hormones: testosterone is the main male reproductive hormone, while oestrogen is the main female reproductive hormone.
- Thinking that secondary sex characteristics appear before puberty: they develop during puberty as hormone levels rise.
- Stating that the pituitary gland produces testosterone or oestrogen: the testes and ovaries produce these hormones, while the pituitary gland releases stimulating hormones.
- Saying oestrogen is produced by the uterus; correct this by naming the ovary as the main production site.
- Confusing oestrogen with progesterone and assigning all cycle-maintenance roles to oestrogen; correct this by stating that progesterone is the main hormone maintaining the uterus lining after ovulation.
- Describing oestrogen as a male hormone or as produced by the testes; correct this by stating that testosterone is the main male reproductive hormone and oestrogen is the main female reproductive hormone.
- Saying that new eggs are made each month after puberty; correct this by stating that a female is born with a store of immature eggs and one matures and is released in a typical cycle.
- Stating that the egg is released from the uterus; correct this by naming the ovary as the site of egg maturation and release.
- Treating 28 days as an exact fixed interval for every person; correct this by describing it as an approximate average with natural variation.
- Defining ovulation as fertilisation; correct this by stating that ovulation is the release of an egg, while fertilisation is the fusion of gametes.
- Saying the egg is released from the uterus; correct this by naming the ovary as the release site.
- Claiming ovulation is caused directly by follicle stimulating hormone alone; correct this by stating that a luteinising hormone surge triggers release, while follicle stimulating hormone stimulates follicle maturation.
- Saying testosterone is produced by the prostate gland or seminal vesicles; correct this by naming the testes as the production site.
- Confusing testosterone with oestrogen and assigning female roles to it; correct this by stating that testosterone is the main male reproductive hormone.
- Stating that testosterone is carried in the sperm or stored in semen; correct this by stating that it is a hormone transported in the bloodstream.
- Thinking that only one hormone controls the cycle; correct this by naming all four hormones and their sources.
- Confusing the roles of FSH and LH; correct this by linking FSH to egg maturation and LH to ovulation.
- Believing oestrogen and progesterone are produced by the pituitary gland; correct this by stating they are produced by the ovaries.
- Saying LH matures the egg; correct this by stating that FSH matures the egg and LH triggers its release.
- Saying oestrogen maintains the lining throughout the cycle; correct this by explaining that oestrogen builds the lining and progesterone maintains it after ovulation.
- Forgetting that progesterone is produced after ovulation by the corpus luteum; correct this by linking progesterone secretion to the remains of the follicle.
- Describing the hormones as acting independently; correct this by showing cause-and-effect links, such as FSH causing oestrogen secretion.
- Omitting feedback control; correct this by stating that progesterone inhibits FSH and LH, and that high oestrogen stimulates LH.
- Confusing positive and negative feedback; correct this by explaining that oestrogen stimulates LH release while progesterone inhibits FSH and LH release.
- Reading the wrong axis or misreading the scale; correct this by checking the units and the value of each major gridline before quoting a number.
- Assuming all hormones peak at the same time; correct this by noting the separate peak days for FSH, oestrogen, LH and progesterone.
- Describing the shape of a curve without linking it to a biological event; correct this by stating what the change in hormone level causes.