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Thyroid

Designed for a 60-second scan in primary care. Use this to explain why this theory fits, what would weaken it, and which tests are most worth discussing.

Why this still fits

I've been experiencing persistent brain fog and fatigue for [DURATION]. I'd like to investigate thyroid contributors with a complete panel rather than relying on TSH alone, especially because the symptom pattern still looks thyroid-like.

What would weaken it

  • -When you DO have energy, do you still enjoy activities you used to love?
  • -Do you snore loudly or gasp/stop breathing during sleep?
  • -Do you get short of breath or your heart races climbing stairs?
  • -Is the fog globally slowed and constant, or is it mainly post-meal, posture-linked, or crash-like?

Key points to communicate

  • TSH is a good first test, but symptoms sometimes persist even when TSH is normal
  • I have specific symptoms that match thyroid: [LIST YOUR SYMPTOMS]
  • 79% of hypothyroid patients report brain fog, and 47% had it BEFORE diagnosis
  • I'd like to test early morning, fasting, for accurate results
  • Please separate metabolic, sleep, autonomic, and medication overlap before narrowing to one cause.

Tests and measurements to discuss

Need the fuller context? Use the test explainers for the measurement itself, or jump back to the tests section on the Thyroid page to see how the tests fit the whole pattern.

What this helps clarify: Primary thyroid screening marker.

Range context

1.0–2.0 mIU/L (optimal)

How to use the result

Save the result with date and symptoms from the same week.

What this helps clarify: Active thyroid hormone that directly affects brain function

Range context

3.0–4.0 pg/mL

How to use the result

Save the result with date and symptoms from the same week.

What this helps clarify: Thyroid hormone precursor — low levels indicate hypothyroidism

Range context

1.0–1.5 ng/dL

How to use the result

Save the result with date and symptoms from the same week.

What this helps clarify: Elevated in Hashimoto's thyroiditis — autoimmune thyroid attack

Range context

<35 IU/mL

How to use the result

Save the result with date and symptoms from the same week.

TG Antibodies

What this helps clarify: Iron storage marker that can affect energy, focus, and cognition.

Range context

40-100 ng/mL

How to use the result

Save the result with date and symptoms from the same week.

What this helps clarify: Patient-facing vitamin B12 explainer route, useful when a story or clinician uses plain language instead of the active-B12 variant.

Range context

Lab context

How to use the result

Save the result with date and symptoms from the same week.

What this helps clarify: Severe deficiency doubles dementia risk

Range context

40–60 ng/mL

How to use the result

Save the result with date and symptoms from the same week.

Reverse T3 (not routine - only discuss if a specialist thinks the broader picture justifies it)

What this helps clarify: Inactive T3 form — elevated during illness, stress, or low-calorie states

Range context

10–24 ng/dL

How to use the result

Save the result with date and symptoms from the same week.

Peer-reviewed references

  1. https://doi.org/10.1016/j.eprac.2021.12.003
  2. https://doi.org/10.1089/thy.2022.0139
  3. https://doi.org/10.1089/thy.2014.0028
  4. Ettleson et al. 2022; NICE NG145; Samuels & Bernstein 2022
  5. Samuels & Bernstein 2022; Wiersinga 2014