Tricky Topics #3 - The Menstrual Cycle

We’ve looked through the Tassomai data, and found some of the topics that our students find the hardest! We’ll post a brief explainer on each of these topics over the next few weeks in the run up to exam season. Give this series a read if you, your child or your students are struggling with any part of Tassomai - even if these particular topics aren’t problematic, we’ll also touch on some common errors students make when answering questions on Tassomai!


The hormones in the menstrual cycle

There are four key hormones involved in the menstrual cycle:

  • Oestrogen

  • Progesterone

  • Follicle Stimulating Hormone (FSH)

  • Luteinising Hormone (LH)

This article is going to go over what these hormones do, how they interact, and when they are released. The menstrual cycle lasts for 28 days.

Here’s an example Tassomai Question:

tricky-topic-3-question.png

This question asks about where progesterone is produced and what it does - but it’s important to know where all the hormones are produced and what they do.

All four hormones are produced constantly, but not the same amount all the time - at certain points in the cycle some will increase in level, while others will drop.

Oestrogen

Oestrogen is perhaps best known for its role during puberty - it causes the development of secondary sexual characteristics - but it also has a key role in the menstrual cycle.

Effect: Oestrogen thickens, repairs and maintains the uterus lining. It also inhibits the release of LH and FSH.

Where is it produced: In the ovaries.

Progesterone

Effect: Progesterone maintains the uterus lining so that if the egg is fertilised it can embed in the uterus lining.

Where is it produced: In the ovaries.

Follicle Stimulating Hormone (FSH)

Effect: FSH causes the egg to mature in the ovary. It also stimulates the ovaries to release oestrogen.

Where it is produced: In the pituitary gland.


Luteinising Hormone (LH)

Effect: LH stimulates the release of the egg.

Where is it produced: In the pituitary gland.

Hormone Source Effects
Oestrogen Ovaries Development of secondary sexual characteristics
Repairs, maintains & thickens uterus lining
Inhibits release of LH & FSH
Progesterone Ovaries Maintains uterus lining
Follicle Stimulating Hormone Pituitary Gland Causes egg to mature
Stimulates ovaries to release oestrogen
Luteinising Hormone Pituitary Gland Causes egg to be released

The Cycle (simplified)

The menstrual cycle can be broken down into 4 stages:

  • Stage A: Days 1-5 - Menstruation

  • Stage B: Days 5-12 - Building uterus lining

  • Stage C: Days 12-15 - Ovulation

  • Stage D: Days 15-28 - Maintenance of uterus lining

Menstruation: For the first 5 days all four hormones are at a pretty constant level as the uterus lining is shed - this is known as the period or menstruation.

Preparing for ovulation: During this time, FSH levels increase causing an egg to mature in the ovary. Meanwhile, oestrogen begins to rise on approximately day 7, reaching a peak on day 12. This builds the uterus lining, meaning that if the egg is fertilised it can be embedded in the uterus

Hormones in the menstrual cycle and the stages   Attribution: Isometrik [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)] - changes have been made to remove information not required for GCSE students

Hormones in the menstrual cycle and the stages

Attribution: Isometrik [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)] - changes have been made to remove information not required for GCSE students

Ovulation: As oestrogen begins to fall on day 12, the next stage of the cycle starts. FSH and LH begin to sharply rise, because they are no longer inhibited by oestrogen, peaking on day 14, before sharply dropping again on day 15. It is this rise in LH which causes the egg to be released.

Maintenance of uterus lining: After the egg is released, LH and FSH fall back to their original levels - they don’t have anything else to do in this cycle. Oestrogen has also fallen back to its original level, but it then begins to gradually rise again - and this is also when progesterone levels start to increase. This is because they both maintain the uterus lining, and they therefore both peak on day 21 (although this is a smaller peak for oestrogen than on day 12). They then both gradually fall back down to their original levels, which they reach on day 28. This is when the cycle restarts, and the uterus lining is shed.


This question

tricky-topic-3-question-correct.png

We now know that it is LH and FSH which are produced in the pituitary gland, and oestrogen and progesterone which are produced in the ovaries - therefore the answer is one of C or D.

We also know that both oestrogen and progesterone maintain the uterus lining - but it is oestrogen, not progesterone, which also inhibits LH and FSH production. Therefore the answer is C - progesterone is produced in the ovaries, and maintains the uterus lining.