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Why FSH is an important measure in female fertility - By Charles Kingsland, Gynecologist
From a reproductive point of view, the difference between men and women is that men are ‘sperm factories’. Men have the ability to make sperm every single day of the week. Women, on the other hand, are egg warehouses, they do not have the ability to make eggs. The average woman has got her full complement of eggs before she is born and from that moment on her eggs will start to die off, even before she starts ovulating around about her fourteenth year.
This means that, in theory, men have the ability to reproduce up until death, which is a characteristic common to all mammals except human females and some species of whales that lose the ability to reproduce some time before they die when they reach the so called, menopause.
There is some evidence to suggest, however, that the average male sperm count has dropped by up to 50% in the last 50 years and many theories have been put forward as to why this is the case. Pollutants in the atmosphere and particularly in the food chain have been implicated and are most likely to be the cause.
Women, on the other hand, are egg warehouses, they do not have the ability to make eggs. The average woman has got her full complement of eggs before she is born and from that moment on her eggs will start to die off, even before she starts ovulating around about her fourteenth year. When she does start ovulating, four or five eggs can die per cycle during this process. At the beginning of the time that she does start ovulating, it is usual that some poorer quality eggs are ovulated initially. Her best eggs start to be released in her late teens and as she gets older, so do her eggs.
For example, this means that if a 35 year old couple are trying to achieve a pregnancy, the man’s sperm may only be 2 or 3 weeks old but the woman’s eggs will be 35 years old. Unlike men, women will lose their fertility as they get older because their eggs age as well. This can account for the reason why women’s fertility decreases as they get over the age of 30, the rate of miscarriage increases and this also answers the question why there is an increased risk in having abnormalities such as Down’s Syndrome. At the age of 35, the risk of a woman having a baby affected by Down’s Syndrome is 1 in 300 but by the age of 45, this has increased to 1 in 45. The most common cause for this is that the woman’s eggs have got older and are more likely to be abnormal or abnormally fertilized.
The way that eggs are matured in the ovary is by an elaborate series or hormones which are driven by two sex hormones produced by the pituitary gland. The pituitary gland is a little gland at the bottom of the brain. If you were to drill a hole through the bridge of the nose, that’s where you would find it! The two sex hormones in question are Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH). Luteinizing Hormone causes the release of a mature follicle but it is Follicle Stimulating Hormone which drives the ovary to mature the eggs.
Follicle Stimulating Hormone is a bit like the accelerator on a car: if your car engine is of very high quality, you don’t have to press the accelerator very hard to make it go. If your car, however, is older or not such a sporty model then you have to press the accelerator harder for it to work. This is exactly what happens with the ovary. If your ovary contains good quality eggs, your brain recognizes this and it doesn’t have to work so hard to drive your ovary to mature and release them, hence the FSH level is low. If, however, your eggs are older or abnormal for any reason, then your brain also recognizes this problem and as a consequence, the FSH level is much higher.
This makes FSH a vitally important hormone to test when assessing egg quality. We know from IVF studies that if your FSH is above a certain level then, to all intents and purposes, your eggs will not fertilize.
Many people are pre-occupied by testing ovulation. All this does is to assess whether you are ovulating eggs or not. It does not give you any information about what quality of egg you are ovulating. FSH does. So therefore when a OB/GYN tests your FSH level, he or she will have a realistic idea as to what the likely quality of your eggs will be if and when you ovulate. It will also give a good idea as to the prognosis i.e. the likelihood of you achieving a pregnancy with those eggs.
Up until now, there have been no tests of egg quality that you can do at home until the launch of Fertell.
A reasonable indication of whether your eggs are good quality or poorer quality is a level of ten international units per liter of FSH in your blood (10 IU/l). Below this level, it is reasonable to conclude that your egg quality is good. If, however, your levels are higher than ten, it may indicate some egg abnormality. FSH can also be measured in urine.
Similarly, as you get older, your FSH level increases to a point where we know that the eggs in your ovaries are simply not fertilizable or indeed, may have run out altogether. This can also be a test of the menopause. The menopause occurs when your eggs have run out and they no longer produce oestrogen, which is the hormone that maintains your body for pregnancy. If you lose your oestrogen you are no longer fertile. You may also suffer the symptoms of loss of oestrogen, commonly hot flushes and sweats which is indicative of the menopause.
In summary, therefore, the measurement of FSH forms a vital part of investigation if a couple is having difficulty achieving a pregnancy or, indeed, is useful for any woman who just wants to know the status of her fertility.
It is best measured at the start of a woman’s cycle when all of her hormones are at a baseline level and can be accurately assessed. At any other time during the cycle, the tests can be misleading as different women have different levels irrespective of their fertility.
