Identify and describe Puberty and Reproductive Hormones, Fertilisation and Early Development and Overview of the Four Key Menstrual Hormones in the context of hormones in human reproduction.
BEEZYREVISOR
GCSE Biology Revision
Learn it. Recall it. Revise it.
GCSE Biology revision
Hormones in human reproduction
Hormonal coordination in humans
Your specification
AQA student objectives
Learning pathway
All · Most · Some
Explain the relationships between Puberty and Reproductive Hormones, Fertilisation and Early Development and Overview of the Four Key Menstrual Hormones and how they contribute to hormones in human reproduction.
Apply and analyse knowledge of Puberty and Reproductive Hormones, Fertilisation and Early Development and Overview of the Four Key Menstrual Hormones to interpret unfamiliar information about hormones in human reproduction.
Revision summary
Key knowledge
Read on screen, then print for Cornell-style active revision.
Puberty and Reproductive Hormones
- Reproductive hormones are released during adolescence, triggering puberty and the development of secondary sex characteristics.
- Testosterone is the main male reproductive hormone, produced by the Leydig cells of the testes, and it stimulates sperm production.
- Oestrogen is the main female reproductive hormone, produced by the ovaries, and it triggers ovulation and the maturation of eggs.
- Secondary sex characteristics in males include increased hair growth, muscle development, voice breaking, and growth of the penis and testes.
- Secondary sex characteristics in females include breast development, widening of the hips, and growth of pubic and underarm hair.
Fertilisation and Early Development
- During reproduction, a sperm and egg fuse in a process called fertilisation to form a zygote.
- The zygote divides by mitosis to form an embryo, whose cells then undergo cell differentiation to develop into specialised tissues.
- For a fertilised egg to implant successfully, the uterus lining must be thick and maintained, which is the role of progesterone.
Overview of the Four Key Menstrual Hormones
- The four hormones involved in the menstrual cycle are follicle stimulating hormone (FSH), luteinising hormone (LH), oestrogen, and progesterone.
- FSH and LH are both produced by the pituitary gland, whereas oestrogen and progesterone are produced by the ovaries.
- The 28-day menstrual cycle is regulated by the rising and falling concentrations of these four hormones working in coordination.
The Menstrual Cycle: Days 1–14
- Between days 1 and 4, the uterus lining breaks down due to low concentrations of oestrogen and progesterone.
- From around day 3, FSH rises and stimulates an egg to begin maturing inside the ovary.
- Between days 4 and 15, oestrogen levels rise, causing the uterus lining to rebuild and thicken.
- At around day 14, a surge in LH triggers ovulation — the release of a mature egg from the ovary.
The Menstrual Cycle: Days 15–28
- After ovulation, progesterone levels rise and remain high between days 15 and 28, maintaining the thick uterus lining.
- If fertilisation does not occur, progesterone levels fall towards day 28, causing the uterus lining to break down and the cycle to repeat.
- If fertilisation does occur, progesterone concentrations are maintained via a positive feedback loop, keeping the uterus lining intact to support the developing embryo.
The Roles of Oestrogen and Progesterone Compared
- Oestrogen is responsible for building up and growing the uterus lining, whereas progesterone is responsible for maintaining it — a common exam distinction.
- Oestrogen also plays a second key role by stimulating a surge in LH, which directly causes ovulation.
- Progesterone inhibits both FSH and LH, preventing further egg development and release during the second half of the cycle.
Hormone Interactions and Feedback Loops (Higher Tier)
- FSH stimulates the release of oestrogen, and when oestrogen levels become sufficiently high, it inhibits further FSH release in a negative feedback loop.
- Oestrogen stimulates the release of LH, which then causes the surge responsible for ovulation at day 14.
- Progesterone inhibits both FSH and LH, suppressing further egg maturation and ovulation whilst the uterus lining is being maintained.
- When oestrogen and progesterone levels fall at the end of the cycle, inhibition of FSH is lifted, allowing FSH to rise again and restart the cycle.
Interpreting Hormone Graphs
- On a hormone graph, FSH and oestrogen are both elevated during days 4 to 14, corresponding to egg maturation and uterus lining growth.
- The sharp peak of LH at approximately day 14 marks ovulation on a graph, often appearing as a distinct spike.
- Progesterone is highest between days 15 and 28, corresponding to the period when the uterus lining is at its thickest.
- When progesterone drops towards day 28 on a graph, this corresponds to the breakdown of the uterus lining and the start of menstruation.
Key Exam Points to Remember
- The menstrual cycle lasts 28 days and involves a precise sequence of hormonal changes that must be learned in order.
- A common exam error is confusing oestrogen (builds the uterus lining) with progesterone (maintains the uterus lining) — ensure you know the difference.
- Ovulation occurs at day 14 and is caused by a surge in LH, not FSH or oestrogen.
- Progesterone inhibits FSH and LH, which is a key example of negative feedback within the menstrual cycle.