PART XI

Medical Rule-Outs

Before optimizing lifestyle, rule out treatable medical causes. These 10 tests catch the conditions most commonly misdiagnosed as "just stress" or "normal aging."

THE ONE THING

Get a full thyroid panel — not just TSH. A "normal" TSH misses subclinical hypothyroidism, Hashimoto's thyroiditis, and reverse T3 dominance. Request TSH, Free T4, Free T3, and TPO antibodies.

TL;DR — FOR FOGGY READERS

  • 1. Foundation tests first: Thyroid panel, ferritin, B12, vitamin D, sleep study
  • 2. Know the "normal" trap: Lab ranges often miss optimal function — optimal ≠ normal
  • 3. Screen for mimics: ADHD, depression, and POTS share 80%+ of brain fog symptoms

Diagnostic Priority Pyramid

FOUNDATION: Thyroid - B12 - D - Ferritin - Sleep Study AUTONOMIC: POTS - Orthostatic Testing ENVIRONMENT: Mold/CIRS - Toxins ADHD - Depression START AT BASE → WORK UP ONLY IF NEGATIVE

The Thyroid Cascade

Hypothalamus TRH Pituitary TSH Thyroid Free T4 Free T3 TPO Antibodies TSH alone misses 30-40% of thyroid dysfunction

Iron-Dopamine Connection

Fe FERRITIN Tyrosine Hydroxylase DOPAMINE Focus - Drive Ferritin <30 = FOG Target: 50-100 ng/mL

Foundation Tests (Start Here)

#01

Full Thyroid Panel

TIER A $$

TSH alone misses 30-40% of thyroid dysfunction. Subclinical hypothyroidism, Hashimoto's, and reverse T3 dominance require the full panel.

WHAT TO REQUEST

TSH, Free T4, Free T3, TPO antibodies, Thyroglobulin antibodies. Consider Reverse T3 if suspicious despite normal panel.

#02

Ferritin (Iron Stores)

TIER A $

Iron is the rate-limiting cofactor for dopamine synthesis. Ferritin below 30 ng/mL causes fog symptoms even without anemia. Lab "normal" range starts too low.

OPTIMAL RANGE

50-100 ng/mL (not the lab "normal" of 12-150). Below 30 = investigate. Below 50 = supplement.

#03

Vitamin B12 + MMA

TIER A $

Serum B12 can be "normal" while tissue B12 is deficient. Methylmalonic acid (MMA) is a functional marker that catches deficiency before serum levels drop.

OPTIMAL RANGE

B12: above 500 pg/mL (not 200). MMA: below 0.4 umol/L. Elevated MMA = functional deficiency regardless of B12 level.

#04

Vitamin D (25-OH)

TIER A $

Vitamin D receptors exist throughout the brain. Deficiency impairs cognition, mood, and immune function. Most people north of 37 degrees latitude are deficient in winter.

OPTIMAL RANGE

40-60 ng/mL (not 30). Below 30 = deficient. Below 20 = severely deficient.

#05

Sleep Study (Polysomnography)

TIER A $$$

Sleep apnea affects 25% of adults and causes severe cognitive impairment. Most cases are undiagnosed. Even mild apnea (AHI 5-15) causes measurable fog.

PROTOCOL

Request in-lab polysomnography (not just home pulse oximetry). UARS (upper airway resistance syndrome) requires in-lab study to detect.

Rule-Out Strategies

Filter by Evidence Tier

All Strategies (10 strategies)

Optimal vs. "Normal" Lab Ranges

MARKER LAB "NORMAL" OPTIMAL NOTES
TSH 0.4-4.5 mIU/L 1.0-2.0 mIU/L Above 2.5 = investigate
Ferritin 12-150 ng/mL 50-100 ng/mL Below 30 = fog symptoms
Vitamin D 30-100 ng/mL 40-60 ng/mL Below 30 = deficient
B12 200-900 pg/mL 500+ pg/mL Also check MMA
Homocysteine 5-15 umol/L <8 umol/L Elevated = B vitamin issue

Script for Your Doctor

"I've been experiencing persistent cognitive symptoms — difficulty concentrating, mental fatigue, and word-finding issues. Before attributing this to stress or aging, I'd like to rule out common medical causes. Could we run a full thyroid panel (TSH, Free T4, Free T3, TPO antibodies), ferritin, vitamin D, B12 with methylmalonic acid, and homocysteine? I'm also concerned about sleep apnea and would like a referral for a sleep study."

Print this page and bring it to your appointment if helpful.

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