Many women come to us after being told:
• “Your TSH is fine, so your thyroid isn’t the issue.”
• Or, “Once we get your TSH under 2.5, you should be good to go.”

Meanwhile, they’re still dealing with:
• Irregular or anovulatory cycles
• Early pregnancy loss
• Implantation failure
• Low progesterone
• Fatigue, cold intolerance, hair loss, constipation

And no one is asking why.

TSH is a signal, not the hormone doing the work

TSH (thyroid stimulating hormone) is your brain asking your thyroid to produce hormones. But TSH itself does not support ovulation, implantation, or early pregnancy. That job belongs to the actual thyroid hormones , T4 and T3, and whether your cells can access and use them.

Optimal thyroid ranges for fertility

(Functional ranges — not lab “normal” ranges)

These are the ranges we use clinically when evaluating fertility and pregnancy outcomes:

TSH (Thyroid Stimulating Hormone)​
Optimal: 0.5 – 2.0 uIU/mL

TSH tells us how hard the brain is pushing the thyroid — not how much usable hormone is available to your tissues.

We regularly see clients conceive outside this range when other markers are strong.

Free T4 (Storage Hormone)​
Optimal: 1.4 – 1.8 ng/dL​
​(Upper half of the reference range)

Free T4 is the raw material your body converts into active thyroid hormone.
Low-normal levels often mean the system is running on reserve.

Free T3 (Active Hormone)​
Optimal: 3.4 – 4.4 pg/mL​
​(Upper third of the reference range)

This is the hormone that actually:
• Supports ovulation
• Drives progesterone production
• Supports uterine lining development
• Fuels early pregnancy metabolism

You can have a “perfect” TSH and still struggle to conceive if Free T3 is low.

Reverse T3​
Optimal: 10-14 ng/dL

Reverse T3 blocks thyroid hormone from entering cells.

High reverse T3 is commonly driven by:
• Chronic stress
• Undereating or low-calorie intake
• Iron deficiency
• Inflammation
• Overtraining

This marker is rarely checked, and yet it’s one of the most common reasons thyroid hormone “looks fine” but isn’t working.

Thyroid Antibodies (TPO & TgAb)​
Optimal: Negative / non-measurable

Even mild or “borderline” antibodies can interfere with implantation, progesterone, and pregnancy maintenance, long before a diagnosis of Hashimoto’s is given.

What doctors often miss

Most fertility workups do not evaluate:
• Free T3 and Free T4 together
• Thyroid hormone conversion
• Reverse T3
• Mineral status that controls thyroid hormone production and activation

As a result, many women are told their thyroid isn’t contributing, when in reality, thyroid hormone is simply not reaching or working at the cellular level.

What we see clinically

We routinely see clients conceive:
• With a higher-than-“ideal” TSH
• Before their TSH is “perfect”
• When Free T3 improves, even if TSH hasn’t normalized yet
• When mineral deficiencies and conversion issues are addressed

Because fertility is not about chasing a single lab value.

It’s about:
• Adequate thyroid hormone availability at reproductive tissues
• Proper ovarian signaling and progesterone production
• Reducing metabolic and inflammatory stress

TSH is one piece of the puzzle, not the whole picture.

If your labs have been labeled “normal” but your body says otherwise, trust that signal. There is more to look at, and much more that can be supported and this is what we do in the Nurture Your Fertility program. We are currently accepting applications. Learn more here!

What to dig deeper into thyroid health and how you can support it? I have a free thyroid training that will help you get started with this!