Why Thyroid Health Matters in Midlife

The thyroid is a small but mighty gland at the base of your neck, and it produces three hormones: T4, T3, and calcitonin. These hormones affect nearly every cell in your body — influencing metabolism, energy, weight, brain function, mood, and even cholesterol levels.

T4, T3, and Why the Ratio Matters

About 80% of what your thyroid produces is T4 (thyroxine) — the inactive form that must be converted into T3 (triiodothyronine) to do its job. T3 makes up the remaining 20%, but it’s four times more powerful than T4. It drives your metabolism and gives your cells energy.

Your thyroid also needs iodine to make both T3 and T4. Without enough iodine, conversion slows — and symptoms like fatigue, brain fog, weight gain, and hair loss can appear.

The Limitations of Checking Only TSH

For years, I ordered only TSH (thyroid-stimulating hormone) to evaluate thyroid function — because that’s what conventional medicine taught us to do. But through my training in personalized and functional medicine, I’ve learned this is not enough.

TSH comes from the brain, not the thyroid itself. It tells your thyroid to make more hormone, but it doesn’t reveal how well your body is converting T4 to T3, or how stress, inflammation, or nutrient status are affecting that process.

That’s why I now check a full thyroid panel, which often includes:

• TSH – the brain’s signal to the thyroid

• Free T4 and Free T3 – active thyroid hormones circulating in your body

• Reverse T3 (sometimes)– a “mirror image” of T3 that blocks its function when the body is under stress

• Thyroid antibodies (TPO, TG) – to screen for autoimmune thyroid disease

  
  

Stress, Cortisol, and Thyroid Function

Here’s where things get really interesting. Cortisol, your primary stress hormone, and thyroid hormones are tightly linked.

When cortisol runs high — from chronic stress, inflammation, or lack of sleep — your body shifts resources toward survival and away from metabolism. The result?

• T3 decreases

• Reverse T3 increases, acting like a brake on metabolism

• Energy crashes, weight gain creeps in, and cholesterol levels rise

  
  

So, if a woman on hormone therapy suddenly feels “off” — low energy, weight gain, or mood changes — I look beyond estrogen and progesterone. We need to think about the adrenals (cortisol) and thyroid as part of the same system.

GLP-1s, Weight Loss, and the Thyroid Connection

Medications like Ozempic and other GLP-1 agonists have become incredibly popular for weight loss. But rapid weight loss releases free radicals, creating oxidative stress that drives cortisol up.

If your thyroid or adrenal system isn’t balanced first, this can backfire — worsening fatigue, inflammation, and weight regain later. In addition, hypothyroidism raises lipid levels, so if your cholesterol climbs, it’s worth asking whether it’s truly a “statin deficiency” or a thyroid issue that needs attention.

Before starting a GLP-1, it’s wise to:

✅ Check a full thyroid panel (not just TSH)

✅ Assess cortisol and adrenal function

✅ Optimize nutrient support (especially iodine, selenium, and iron)

The Bottom Line

The thyroid is your body’s engine. When cortisol and thyroid are balanced, metabolism hums, energy feels steady, and weight and cholesterol respond more predictably.

If things go awry during menopause — despite optimized hormone replacement — it’s not just about estrogen and progesterone. At Dragonfly Menopause Care, I look deeper into thyroid and adrenal function to help you truly feel like yourself again.