This is education, not medical advice. Nothing here is a diagnosis or a promise about your fertility. Take every number below to your own provider and read it as part of the bigger picture, never on its own.
Hormone signaling is the running conversation between your brain, your thyroid and your ovaries. It decides whether you ovulate, how well, and whether the lining is ready afterwards. A "normal" hormone panel can miss problems in that conversation, because a reference range only describes where about 95% of a tested population lands. It was never set as a target for conception. The results I see misread most often are TSH (and the thyroid antibody hardly anyone orders), mid-luteal progesterone drawn on the wrong day, and outliers such as prolactin or the LH:FSH ratio. What counts is how those values sit next to each other.
If your fertility bloods came back "all normal" and you are still waiting, this part of the picture probably feels like a locked door. The panel looks fine. Your doctor moves on to the next patient. You go home with a printout full of numbers and nobody has told you what they mean for your chances this month.
I want to change how you look at that printout. Hormones don't behave like a shopping list of separate values. Each one is a message that triggers the next, and when you read them one flag at a time, the important detail usually slips through the gaps between them.
What is "hormone signaling," and why does it decide conception?
Ovulation is the final step of a chain of messages. Your hypothalamus signals the pituitary gland. The pituitary releases FSH and LH, which tell an ovary to mature an egg and let it go. After ovulation, the ovary makes progesterone to get the uterine lining ready for implantation. Your thyroid sits over the whole process and sets the pace. If one link runs slightly slow or weak, every lab value can still land inside its range while the timing and the follow-through are off.
So "normal" and "ready to conceive" answer two different questions. A range that describes the general population says very little about what is happening inside one woman's cycle. That is why the day a sample was drawn, the antibody result and the pattern across several markers tell you more than any single number.
Your thyroid: the number, and the antibody nobody checks
What should my TSH be if I'm trying to conceive?
TSH (thyroid-stimulating hormone) is the most useful single thyroid number, and your thyroid sets the pace for ovulation and early pregnancy. Many labs call a TSH "normal" up to about 4 to 4.5 mIU/L. The American Thyroid Association, however, recommends a TSH below 2.5 mIU/L before pregnancy for women who are already being treated for hypothyroidism. Online, you will see that 2.5 figure quoted as if it applied to every woman trying to conceive. It doesn't.
Experts genuinely disagree here. In its 2024 guidance, the American Society for Reproductive Medicine found insufficient evidence that a TSH between 2.5 and 4, without thyroid antibodies, worsens outcomes for women trying to conceive in general. So I would never tell you that your 3.2 is the reason. I would tell you that a TSH in the high 2s or the 3s deserves a second look together with your antibody result, rather than a quick "that's fine."
The antibody that matters even when your TSH is normal
The marker I most often find missing from a client's file is thyroid peroxidase antibodies (TPO antibodies). You can have a perfectly normal TSH and still have an autoimmune process going on in your thyroid. In a large body of research on women without obvious thyroid disease, a positive antibody test has been linked to a clearly higher risk of miscarriage. One frequently cited review put it at roughly two to four times the risk. It has also been linked to lower fertility in women with recurrent loss or infertility.
First, this is an association. Antibodies flag a higher risk, and they cannot prove that they are the cause in any one woman. Second, large trials have not shown that giving thyroid hormone (levothyroxine) to antibody-positive women with a normal TSH improves live-birth rates. So the point of the TPO test is not to secure a prescription. The result tells your provider how closely to watch your thyroid, particularly in early pregnancy, when a fair number of antibody-positive women slide into subclinical hypothyroidism. Ask for the test, then read the result together with your provider.
Progesterone: the hormone where timing is everything
Your ovary makes progesterone after you ovulate. A level taken at the right moment confirms that ovulation happened and gives a rough idea of how strong it was. Timing is where most results go wrong. Progesterone peaks around seven days after ovulation. In a textbook 28-day cycle that falls on about day 21. If you ovulate later, it falls later (how to find your own test day). A mid-luteal level above roughly 10 ng/mL is the figure commonly used to confirm ovulation.
"Low progesterone" is not a tidy diagnosis. According to an ASRM committee opinion, there is no validated, standardized test for luteal phase deficiency, and it has not been established as a cause of infertility in its own right. The most useful thing to check is the date on the lab slip. If you actually ovulated on day 18 or day 24, a sample drawn on "day 21" can come back falsely low. With cycles that aren't 28 days long, the standard test is very often just taken on the wrong day, and in that case your hormones are fine and the reading is what went wrong.
The ratios and the outliers: LH:FSH and prolactin
Two further results are worth more than a glance. The LH:FSH ratio can point toward the pattern seen in PCOS, where LH tends to run high compared with FSH. PCOS is diagnosed from several features together, though, never from a ratio, and it overlaps heavily with metabolic health. Prolactin, best known for its role in breastfeeding, can shut down the ovulation signal entirely when it is raised. A standard fertility panel often leaves it out unless somebody thinks to add it.
Neither result should alarm you when you look at it alone. Both make the same point I keep coming back to, which is that the answer usually lies in how these hormones relate to one another.
When your cycle is itself the signal
Your period is a monthly report on the whole signaling chain. It costs nothing and it carries more information than most single blood tests. Cycles that run steadily between 24 and 35 days, with a luteal phase of about 10 days or more, suggest the chain is completing. Cycles that are very long, very short, unpredictable or missing tell you something is breaking down along the way. Ovulation may be late, weak or not happening.
For that reason, "How long are your cycles, and how regular are they?" often tells me more than one blood draw. A short luteal phase leads back to the progesterone question above. Long or irregular cycles lead toward the trigger for ovulation, and often toward blood sugar and insulin, which can push the LH signal off course. Your cycle doesn't replace lab work. It shows you which tests to run and on which day they will actually mean something.
Why hormone signaling can't be read alone
Here is a detail that surprises most women. Your thyroid depends on nutrients to do its job. Iron is a building block of thyroid peroxidase, the enzyme that produces thyroid hormone, and iron deficiency can lower thyroid hormone levels and slow the conversion of the storage form (T4) into the active form (T3). Selenium drives that same conversion through a group of enzymes called deiodinases. A TSH that looks a little off may therefore be a nutrient problem showing up in your thyroid results.
This is exactly why I read labs as a set. A hormone value reflects everything around it, including the nutrients feeding it and the metabolic patterns pushing on it. Look at it in isolation and you can easily miss the real cause.
So what should I actually do with all this?
You don't need to walk in demanding a long list of tests. A calm, specific request works better, followed by a proper discussion of the results. You could say something like:
"Could we look at my TSH together with thyroid (TPO) antibodies, and a progesterone timed to my own ovulation? And where everything is in range, could we go through the results together, against my cycle, rather than one by one?"
If your cycles are irregular, add prolactin and ask to look at LH and FSH side by side.
That conversation moves you away from "your hormones are normal, keep trying" and toward an understanding of how your signaling is actually working and where to start. I can't promise you an outcome, and none of this replaces your doctor. What it gives you is a far better appointment.