FSH

Let's talk about FSH (Follicle Stimulating Hormone). FSH is one of the first things a doctor will test if you want to do IVF or egg freezing or are having any fertility issues.

- FSH is a hormone - it helps follicles develop eggs. It's a good thing.
- Ovaries that are older need more help - they need more FSH
- Your ovaries "know" how how many eggs they've got left (and how "old" they are), and ask the brain to tell the pituitary gland to make an amount of FSH roughly corresponding to how much they need to bring an egg to maturity.
- The older your ovaries are/fewer eggs they have/ the more help they need - the more FSH they ask for
- Ovaries only get older - never younger. No new eggs are created. You have all the eggs you'll ever have at birth.
- If you test the levels of FSH in the bloodstream, you can tell how much help the ovaries are asking for. This is the best indicator of their "age" - which doesn't exactly correspond to a woman's biological age (different women have different fertility - some hit menopause late, some early, etc). So this is why doctors treat FSH level as such an important thing - it gives insight into the age/quality of the ovaries and eggs.
- FSH might fluctuate slightly month to month, but that doesn't mean the ovaries are in better shape or that there are suddenly more eggs. Eggs are lost every month.
- In general, consensus is that levels less than 10 are considered ok, though lower is better. Lower FSH's correspond with better rates of IVF and egg production. Different fertility clinics set cutoffs at different levels. For example, if someone has an FSH of 20, she'll probably not find a clinic willing to treat her - it just means the ovaries are too old and won't make any eggs good enough to make a baby.
- If FSH was 13 one month and 12 the next month, it's not like the odds are any better. FSH is not itself the problem. The problem is that the ovaries ever asked for that much help.

In my training class (which was all egg freezers - though most were late 30's or early 40's) , this one woman was talking about how she wanted to do freezing a few months earlier, but had to postpone it. She now "realizes" in retrospect that this was good, because her FSH measured slightly lower when she just now had it retested. So in her belief, her odds were better now than they were a few months ago. But that's not true - she didn't suddenly have more eggs or younger ovaries ... and that's all that mattered. The hormone level just fluctuated for one reason or another.

Prognosis for egg retrieval is a function of the highest FSH you've ever had. Fluctuations down don't mean anything meaningful. Taking something to "lower" FSH wouldn't help. I've heard women ask if there were ways to lower FSH (doctors care so much about elevated levels, so lowering the level would be good, right?). But a lowered level doesn't create more young eggs. Preventing the needed/helpful hormone from being created doesn't make the eggs themselves any healthier or more viable. So, well ... that's that.

FSH is tested on day 3 of the menstrual cycle. This is the baseline day for testing hormones. Another thing they test is estrogen/estradiol, because estrogen can artificially lower FSH. So suppose FSH comes back at 7 - that's good - a great prognosis for IVF chances assuming the woman is also under 37 or 38. But if estrogen came back at 100, that would be bad - it would mean FSH might really be naturally higher than 7. Doctors will only trust the FSH number if the estradiol level comes back low enough to rule out that it's masking the true FSH level.

So what do doctors like to see?

FSH < 10
Estrogen < 50

Although there are still plenty of IVF babies born to women with values outside this range (though not too far off), those limits are the ones that have the best results.

Science lesson for the day!