How Your Thyroid Affects Your Hormones

Your thyroid might be small, but it plays a massive role in your overall health—especially when it comes to your hormones, cycle, and ability to conceive. Many women don’t realize that an underperforming thyroid could be the missing puzzle piece in optimizing their cycle and fertility.

Let’s break down why your thyroid is so critical to your hormone health.

What Is the Thyroid, and What Does It Do?

The thyroid is a butterfly-shaped gland located in your neck. It produces hormones—primarily T3 (triiodothyronine) and T4 (thyroxine)—that regulate your metabolism, energy levels, and more.

But its influence doesn’t stop there. These hormones play a direct role in:

Maintaining healthy reproductive hormone levels
Supporting a regular menstrual cycle
Creating an optimal environment for conception and pregnancy

When your thyroid isn’t functioning properly—whether it’s underactive (hypothyroidism) or overactive (hyperthyroidism)—it can send ripples through your entire endocrine system, affecting ovulation, cycle regularity, and even your chances of getting pregnant.

How Thyroid Health Affects Hormones

The thyroid and reproductive hormones are closely connected. Here’s how:

Estrogen and Progesterone

An imbalanced thyroid can disrupt the estrogen-to-progesterone ratio, leading to symptoms like irregular cycles, PMS, or heavy periods.

Ovulation and the Luteal Phase

Thyroid issues can interfere with ovulation and shorten your luteal phase, making it harder for implantation to occur.

Stress Hormones

Thyroid dysfunction often leads to elevated cortisol levels, which can further disrupt reproductive hormones.

How Thyroid Issues Impact Your Cycle & Fertility

Optimal thyroid function is essential for a predictable, healthy menstrual cycle and for getting pregnant. Here’s how thyroid issues can affect your cycle and fertility:

Irregular Cycles: Sub-optimal thyroid function can lead to long or short cycles
Missed Periods: Hypothyroidism can lead to anovulatory cycles (where ovulation doesn’t occur)
Heavy or Light Periods: Both extremes are linked to thyroid imbalances, as they affect uterine lining development
Ovulation: Thyroid hormones directly influence the release of eggs during ovulation. Without ovulation, pregnancy isn’t possible
Uterine Lining: A properly functioning thyroid helps ensure the uterine lining is thick enough for implantation
Pregnancy Maintenance: Hypothyroidism increases the risk of early miscarriage, making optimal thyroid function critical for sustaining a pregnancy

Signs Your Thyroid Might Need Attention

If you’re experiencing any of the symptoms below, I highly recommend digging deeper into your thyroid health. I actually recommend a full thyroid panel as part of yearly bloodwork.

Fatigue or low energy
Weight changes (gain or loss) that don’t align with diet or activity
Hair thinning or hair loss
Sensitivity to cold or heat
Irregular, heavy, or missed periods
Difficulty conceiving or recurrent miscarriage

Assessing Your Thyroid

As mentioned above, I recommend getting a full thyroid panel (see below) and an HTMA yearly to get the full picture of thyroid health.

I also recommend using tighter lab ranges, as we want to see the thyroid functioning optimally, not just within “normal” limits.

Lastly, I often have clients complete an Iodine Loading Test to assess iodine status. Iodine plays a CRITICAL role in thyroid function and is often a missing piece in healing thyroid issues, optimizing fertility, and supporting healthy cycles.