In an eggshell...
- FSH levels promote growing follicles in our ovaries to grow mature eggs
- FSH levels change during the menstrual cycle and decline as we age
- During egg freezing, FSH is taken as a marker alongside AMH to assess reproductive health
FSH or follicle-stimulating hormone does what it says on the tin.
It stimulates growing follicles in the ovaries to produce mature eggs every month.
In fact, it’s on the board of directors along with other hormones that orchestrate the menstrual cycle 👩⚖️
Given that FSH has such a key role in developing our eggs, it’s only natural for it to play a bigger role in our fertility, and related treatments such as egg freezing.
So we’re here with this digestible guide on FSH levels, how to test them, interpret results and how they impact your fertility!
Read on!
What is FSH?
FSH, or Follicle Stimulating Hormone is produced by the pituitary glands and signals the growing follicles in our ovaries to grow and develop mature eggs.
Here’s how it works:
🧠 pituitary gland produces FSH
🪺 FSH acts on the growing follicles in the ovaries
🥚 the growing follicles secrete oestrogen once they pass their initial stage of growth
🧠 the brain senses oestrogen release, which then acts as a signal to reduce FSH production
🥚 oestrogen takes over, and the follicles go on to mature and release an egg
FSH rises and falls along with other hormones during different stages of the menstrual cycle, telling your ovaries when it's time to grow and release a mature egg.
What are normal FSH levels like?
Just like a roller coaster 🎢, FSH levels have their ups and downs throughout your menstrual cycle.
Here is what FSH levels look like during different phases:
Normal FSH levels by age (+chart)
As you can see above, FSH levels tend to fluctuate during different phases. Apart from this, as we age, FSH levels also increase. Here’s what it looks like:
Why do FSH levels increase with age?
As you age, your FSH levels tend to increase. But why, exactly?
Let’s nerd it out here to understand.
As women, we are born with all the eggs we will ever have, aka, around 2 million eggs at birth. This reaches to around 400,000 at the time of puberty.
As our menstrual cycle starts, a set of follicles are selected every month, in a race to produce the “mature egg of the month” 👑
As follicles keep getting recruited with every cycle and as we age, our ovarian reserve decreases.
Here's what happens then:
1. Fewer eggs = fewer follicles growing each month
2. Fewer follicles = less oestrogen produced
3. Less oestrogen = brain panics and sends more FSH as a signal boost
Result? A depleting egg reserve as we age leads to less oestrogen. The brain doesn’t get a signal from oestrogen to reduce FSH production. Hence, FSH levels keep on increasing.
How to know my FSH levels?
Checking for your FSH levels involves a simple blood test at the doctor’s office.
A healthcare professional will collect a blood sample from a vein in your arm using a needle. You may feel a small sting, but that’s pretty much it! This takes less than 5 minutes.
When should I take an FSH test?
The best time to check your FSH levels is on day 3 of your menstrual cycle. Because that's when FSH is at its baseline, giving you the most accurate picture of your ovarian function.
Since FSH levels tend to fluctuate throughout your cycle, it’s commonly recommended to measure it along with oestradiol to be interpretable.
What causes high FSH levels?
If your blood test results indicate high FSH, it’s a possibility that the control centre (pituitary gland) is overproducing FSH.
But to really figure out the reason why, it’s best to visit your doctor and work out the reason. Here are some reasons for high FSH levels:
1. Perimenopause or menopause
Perimenopause or menopause is when our ovarian reserve declines significantly, leading to a natural increase in FSH to trigger follicle growth. This is age-related and normal increase in FSH.
2. Polycystic Ovary Syndrome (PCOS)
Women with PCOS tend to have hormone imbalances and menstrual irregularities. In fact, studies mention that with PCOS, there’s a disturbance in how the (gonadotropin-releasing hormone) is secreted, leading to an increase in FSH and LH hormones.
🍿Freebie alert: Download our free PCOS guide
3. Primary ovarian insufficiency (POI)
This is a condition where you experience menopause-like symptoms and your ovaries stop working normally when you’re younger than 40, due to genetic reasons or illnesses. This also leads to high FSH levels.
4. Pituitary or hypothalamic dysfunction or tumours
Some growth hormone-secreting pituitary tumours may secrete high levels of FSH, followed by low levels of LH.
5. Genetic issues
Let’s nerd it out for a bit here. As women, we have 45 chromosomes plus 1 sex chromosome, which is XX in our case.
One such condition is Turner’s syndrome, which occurs when one of the X chromosomes is missing, partially, or completely.
Turner’s syndrome causes symptoms such as delayed puberty, lack of periods, and primary ovarian insufficiency, and in turn, high FSH levels (in the postmenopausal range) in women.
What if my FSH levels are too low?
It’s quite uncommon to have low FSH levels.
Some common symptoms may include irregular or longer menstrual cycles, but here are some reasons why it may be on the lower end:
1. Issues with the hypothalamus or pituitary
The hypothalamus is the headquarters for deciding the hormones to be produced. If it does not produce enough GnRH (gonadotropin-releasing hormone), the pituitary gland won’t receive the signal to produce enough FSH.
2. Thyroid disorders
Some studies report FSH levels to be unchanged or decreased in cases such as hyperthyroidism.
📚Also read: Does Low Thyroid Affect My Fertility?
3. Intense exercise
It is possible for regular, intense exercise suppresses ovarian hormones, such as FSH.
4. Being severely underweight or recent rapid weight loss
Either of these conditions can interfere with the hormonal balance. Low body fat is associated with less oestrogen, which can also slow FSH release.
FSH Levels and Egg Freezing: What's the Connection?
Now, let's talk about how FSH levels relate to egg freezing.
When considering egg freezing, your FSH levels can give you and your doctor insights about your ovarian reserve. Here's how:
1. Predicting response to stimulation
Lower FSH levels generally indicate a better response to the hormonal stimulation used in egg freezing. This means you might produce more eggs per cycle.
For instance, here’s a general idea of how FSH levels correlate with egg freezing:
As per a study,
- FSH levels lesser than 15 mIU/mL might expect a good response to egg-freezing medication
- FSH levels between 15 mIU/ml and 24.9 mIU/mL might expect a moderate response
- FSH levels over 25 mIU/ml, might indicate a low ovarian reserve with reduced pregnancy rates per attempt
2. Determining the best time to freeze
If your FSH levels are starting to creep up, it might be a sign that it's time to consider egg freezing sooner rather than later.
3. Personalising your protocol
Your doctor can use your FSH levels and other factors to tailor the egg-freezing process to your unique needs. This also helps them decide the dosage of FSH to provide during the egg-freezing cycle.
Ultimately, knowing your FSH levels can help you and your doctor discuss potential outcomes and decide how many cycles you might need.
Remember, while FSH is important, it's not the only factor. Your age, AMH levels, AFC and overall health play a crucial role in the egg-freezing process.
How Amilis can help
While FSH is crucial, it’s just one marker of your ovarian reserve.
FSH varies based on lifestyle and menstrual cycles, making it an addition rather than a complete marker of your ovarian reserve.
This is also why fertility specialists recommend taking an AMH test along with FSH to get the full picture.
If you're considering egg freezing or just curious about your fertility, here’s how Amilis can help:
- Affordable AMH tests in the UK (50% less than private clinics!)
- Free 1-1 consultations with Amilis experts (have questions on your fertility or egg freezing? Get them all answered!)
- Free consultations with top, vetted fertility clinics in London (chat with a fertility specialist, with zero appointment fees)
If you’re not there yet, there’s still a personalised egg-freezing quiz that you can take to get started.
Regardless, knowing your fertility levels is still a step towards you caring for your reproductive health, on your own terms 🫶
Here’s to making fertility testing accessible and affordable in the UK, one step at a time! ❤️
Frequently Asked Questions
1. What should FSH levels be for egg retrieval?
For successful egg retrieval, optimal FSH levels are typically below 10 mIU/mL, as this suggests a better ovarian reserve and response to stimulation. Levels between 10 and 15 mIU/mL may still allow for egg retrieval but might result in fewer eggs. Levels above 15 mIU/mL often indicate diminished ovarian reserve and may require adjustments in treatment protocols.
2. Does high FSH mean poor egg quality?
High FSH levels are often associated with poor egg quality because they indicate that the ovaries require more stimulation to produce eggs, which can be a sign of diminished ovarian reserve. But it’s not a definitive predictor, as some women with high FSH still do produce good quality eggs and can still have successful egg freezing or IVF outcomes depending on other factors.
3. What FSH level indicates menopause?
FSH levels consistently above 30 mIU/mL, combined with the absence of menstrual periods for 12 months, typically indicate menopause. However, the transition to menopause (perimenopause) can cause fluctuations in FSH levels, so your doctor will likely consider other factors too.
