When you are missing your period, it is important to figure out WHY. The path forward varies a lot depending on diagnosis. Chapter 4 in No Period. Now What? goes through the standard diagnostic procedure, including bloodwork and results to expect; here I'm just going to talk about the bloodwork that is helpful.
The possible causes when you've had a period, but it's disappeared (secondary amenorrhea) include:
Polycystic ovarian syndrome (PCOS)
Hypothalamic amenorrhea (HA) also known as hypogonadotropic hypogonadism (HH)
Over- or under-active thyroid
Elevated prolactin
Primary Ovarian Insufficiency (POI) also known as premature menopause (under 40)
Asherman's syndrome
Menopause (over 40)
All of these things could also fall under the umbrella of "post-pill amenorrhea." The term doesn’t refer to a specific condition, but it describes the situation of your period not returning after discontinuing the pill or other hormonal birth control. If your period hasn’t returned by a couple of months after stopping the pill, and you had a normal period before starting, it’s likely that the cause is something that changed while you were on the pill—not the pill itself.
If you've never had a natural period, that's called primary amenorrhea, and all the above are possibilities as well as some genetic and physical conditions that are beyond the scope of this blog.
(One other point to note is that underfueling/overexercise/stress can sometimes cause either short or long cycles, or cycles where you are not in fact ovulating. If this is the case for you, hormonal testing can help determine if there is another cause for this "oligomenorrhea", like PCOS. If your hormones are all normal, and some of the HA-related behaviors ring true for you, then it's absolutely worth going ALL IN to see if it helps make your cycles more regular.)
When to test?
It is standard, when testing for hormones related to the menstrual cycle, to test on "Cycle Day 3 (CD3)" where CD1 is the first day of your period.
Of course, if you have amenorrhea, you don't HAVE a period! With most of these conditions, your hormones are essentially in a steady state, at baseline, so you can test at any time.
If you happen to have a follicle growing, or have ovulated but didn't know it, the estradiol and progesterone would tell you that. In those cases, you can assess your other hormones by looking at changes in hormones through the menstrual cycle as described in this blog post.
Reproductive hormones:
These hormones can indicate hypothalamic amenorrhea, normal, primary ovarian insufficiency (aka premature menopause), or menopause. While FSH:LH ratio can be elevated in PCOS, it is NOT diagnostic.
FSH (Follicle Stimulating Hormone) - general indicator of "egg reserve"
LH (Luteinizing Hormone) - best marker of the status of your hypothalamus
Estradiol - indicative of the status of growth of follicles
Progesterone - have you ovulated recently or not?
Hormones to assess other causes of amenorrhea
Prolactin - Hyperprolactinemia will suppress reproductive hormones
TSH (Thyroid Stimulating Hormone) - can also be related to prolactin, can suppress reproductive hormones if out of range either high or low
Free Testosterone - can indicate PCOS, along with dihydrotestosterone, androstenedione, and DHEAS
17-OH-progesterone - can indicate adrenal hyperplasia
3. Other hormones that are sometimes tested, but not necessary:
SHBG (sex hormone binding globulin): Can correlate with HA or PCOS, but not diagnostic
AMH (anti-mullerian hormone): Can correlate with egg reserve, but not diagnostic
This list would allow you and your doctor to rule in/out the most common causes of amenorrhea. Both PCOS and HA are diagnoses of exclusion, but as I discuss in the HA vs PCOS chapter of No Period. Now What? (available for free here), HA must be excluded before a PCOS diagnosis is made.
What does it mean?
It is a little challenging for me to tell you what to expect with each of the different conditions, because while there are some commonalities, there are also ranges that can overlap and one has to consider not only the bloodwork, but also history, possibly ultrasound, and potentially other tests.
Generally, I would expect the following:
HA: almost all of these hormones will be low, or at the low end of the "normal" range. SHBG probably high.
PCOS: FSH normal, LH normal to high, free testosterone, androstenedione, DHEAS, dihydrotestosterone likely elevated. SHBG probably low.
POI (age <40) or menopause (age >40): FSH and LH will be high
Elevated prolactin: Prolactin high, FSH and LH probably low, or low end of the normal range.
Over- or under-active thyroid: TSH that is outside the normal range, possibly low FSH and LH.
Asherman's syndrome: All hormones normal.
It is possible to have HA with "normal" hormones, and that is where a deeper dive into history can be particularly helpful.
Learn more in NPNW, and if you have bloodwork but haven't been given a good explanation, you can chat with me.
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