The Most Notorious Lie Told to Women About Their Thyroid
- Renee Grandi
- Apr 15
- 4 min read
Updated: Apr 15
If you’re a woman who’s ever walked into a clinic exhausted, freezing, bloated, and losing hair in clumps only to be told “your thyroid is fine,” then this article is for you. One of the most pervasive lies in modern medicine is that if your thyroid-stimulating hormone (TSH) is within the lab reference range, then your thyroid must be functioning normally. This false reassurance keeps countless women undiagnosed, undertreated, and dismissed for years. Let’s uncover the deeper biochemistry behind this and why TSH alone is never the whole picture.
TSH Is Just the Messenger, Not the Message
TSH is a pituitary hormone, not a thyroid hormone. It’s secreted by the brain to signal the thyroid gland to produce T4 (thyroxine) and, to a lesser extent, T3 (triiodothyronine), which is the active hormone responsible for regulating metabolism, brain function, temperature, digestion, cardiovascular health, reproductive hormones, and more.
When your TSH is high, it suggests your brain is screaming at the thyroid to work harder, often indicating hypothyroidism. When TSH is low, it can suggest an overactive thyroid or, in some cases, a feedback disruption. But here's the problem: TSH can fall within “normal” even when the thyroid is underperforming, especially in early autoimmune thyroid disease, peripheral conversion disorders, pituitary dysfunction, or when nutrient deficiencies disrupt hormone pathways.
Why Normal TSH Doesn't Equal Optimal Thyroid Function
The range for TSH is often too broad, typically spanning from 0.5 to 4.5 mIU/L, though most functional and integrative practitioners agree that optimal TSH sits closer to 1.0–2.5. Many women experience clear thyroid symptoms: fatigue, constipation, brain fog, irregular periods, weight gain, low mood, and infertility—with TSH results around 3.5 or 4.2, yet are told they're “fine”. This misleads women into thinking their symptoms must be unrelated or, worse, psychological. Worse still, TSH doesn't reflect what’s happening at the tissue level, how your body converts T4 to T3, or whether reverse T3 blocks receptor activity. It also cannot detect autoimmune thyroid attacks unless antibodies are tested.
Understanding How the Thyroid Functions Biochemically
The thyroid relies on an elegant series of hormonal signals, enzyme conversions, and nutrient cofactors to function correctly. The hypothalamus sends TRH (thyrotropin-releasing hormone) to the pituitary, which releases TSH to stimulate the thyroid gland. The thyroid then produces about 90–93% T4 and only 7–10% T3. But here’s the key: T4 is inactive. It must be converted into T3 in the liver, gut, and other tissues.
This conversion process is delicate and highly dependent on:
Selenium (cofactor for deiodinase enzymes)
Zinc and magnesium (critical for receptor sensitivity and enzyme activity)
Iron (needed for TPO, the enzyme that produces thyroid hormone)
Adequate cortisol and balanced stress response
A healthy gut microbiome
When these are missing or chronic inflammation is present, the conversion falters. T3 may drop, reverse T3 may rise, and the body will slow down, all while TSH appears “normal”.
What About Autoimmunity?
Hashimoto’s thyroiditis, the most common cause of hypothyroidism in women, is an autoimmune disease, not a thyroid disease per se. The immune system attacks thyroid tissue, often years before hormone levels fall out of range. Women may cycle between normal and subclinical results for years, never being told that TPO or Tg antibodies are elevated, never knowing they’re in the autoimmune phase.
Similarly, Graves’ disease is an autoimmune hyperthyroid condition driven by TRAb antibodies that stimulate the TSH receptor. These immune patterns remain invisible without antibody testing, and patients are often misdiagnosed or under-monitored.
The Interconnected Web of the Thyroid
Your thyroid doesn’t function in isolation. It’s intrinsically connected with your:
Adrenal system: Cortisol imbalances affect T4 to T3 conversion and receptor sensitivity.
Gut: Approximately 20% of T4 to T3 conversion occurs via gut bacteria. Dysbiosis, inflammation, and leaky gut directly impair thyroid function.
Liver: The liver processes over 60% of thyroid hormone conversion. Liver congestion, toxicity, or non-alcoholic fatty liver disease will bottleneck this pathway.
Ovaries: Oestrogen dominance, PCOS, and progesterone deficiency influence thyroid-binding globulin (TBG) levels and hormone signalling.
Immune system: Chronic infections like Epstein-Barr Virus (EBV), gut pathogens, or even past viral triggers can set off autoimmunity, altering the thyroid's structural integrity and function.
This means fatigue, poor stress tolerance, infertility, acne, weight fluctuations, and even perimenopausal symptoms can all be downstream effects of underperforming thyroid activity, even with a “normal” TSH.
Nutrient Depletion Is the Hidden Factor
The thyroid requires a steady supply of nutrients to maintain normal function. But women today are commonly depleted in:
Iron and ferritin: Crucial for TPO and thyroid hormone synthesis
Selenium: Needed for both antioxidant defence and hormone conversion
Iodine: Foundational for the thyroid hormone structure, but risky in excess during autoimmunity
Zinc and B6: essential for hormone receptor binding and neurotransmitter regulation
Magnesium: supports adrenal health, thyroid enzyme activity, and temperature regulation
Vitamin D: modulates immune balance and inflammation
Worse still, chronic stress, poor digestion, the pill, and even over-exercising steal or deplete many of these nutrients. If you don’t address these imbalances, no amount of T4-only medication will fix the deeper dysfunction.
Why Women Are Dismissed
The prevailing model of thyroid care is outdated. It waits until overt dysfunction is evident on TSH labs, ignores the presence of antibodies unless it’s “bad enough”, and dismisses symptoms as depression, aging, or anxiety. Women are told it's all in their head when, in fact, it’s in their mitochondria, their enzyme pathways, their gut, and their immune signalling. This model fails because it treats numbers, not people. Women deserve comprehensive investigation, including TSH, free T4, free T3, reverse T3, thyroid antibodies (TPO, Tg, TRAb), nutrient panels, and stress and gut function assessment.
They deserve to know if their fatigue, cycle changes, infertility, or mood swings are rooted in an undiagnosed thyroid imbalance.
Your Next Steps
If your labs are “normal” but you feel anything but, it’s time to go deeper. Don’t let the TSH myth keep you in the dark. You know your body better than any reference range ever could. At the Women’s Integrative Health Clinic, I specialise in uncovering the missing links between thyroid dysfunction, nutrient depletion, immune imbalances, and the biochemical disruptions that drive your symptoms. Our assessments are tailored to investigate the whole picture so you can feel like yourself again.
🩺 Book a functional thyroid assessment at and let’s get to the root cause together.
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