Primary Causes & Action Plans

TSH

The pituitary signal controlling thyroid output
Thyroid-stimulating hormone (TSH) is produced by the pituitary gland to regulate thyroid hormone production. It is the most commonly ordered thyroid test. When thyroid hormones are low, TSH rises to stimulate more production. When thyroid hormones are high, TSH drops. However, TSH alone can miss many thyroid problems.
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Target 1.0 - 2.0 mIU/L (optimal)
Suggested Action Plan

If TSH is outside the optimal range, request a full thyroid panel including Free T4, Free T3, TPO Antibodies, and Reverse T3 before drawing conclusions. TSH alone does not tell the whole story.

Free T4

The main thyroid hormone output
Free T4 (thyroxine) is the unbound, biologically available form of the primary hormone produced by the thyroid gland. T4 is a prohormone that must be converted to T3 (the active form) by deiodinase enzymes in peripheral tissues. Measuring Free T4 tells you how much raw material the thyroid is producing.
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Target 1.2 - 1.5 ng/dL (optimal)
Suggested Action Plan

If Free T4 is low with elevated TSH, hypothyroidism is likely and thyroid hormone replacement (levothyroxine) may be needed. If Free T4 is normal but Free T3 is low, investigate conversion issues (nutrient deficiencies, stress, inflammation).

Free T3

The active thyroid hormone driving metabolism
Free T3 (triiodothyronine) is the biologically active thyroid hormone responsible for regulating metabolism, energy production, body temperature, heart rate, and brain function. It is approximately 4-5 times more potent than T4. Most T3 is produced by peripheral conversion of T4, not directly by the thyroid gland.
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Target 3.2 - 4.0 pg/mL (optimal)
Suggested Action Plan

If Free T3 is low despite normal TSH and T4, investigate conversion issues. Ensure adequate selenium (200 mcg/day), zinc (30 mg/day), and iron. Reduce chronic stress. Address gut health and inflammation. Some patients benefit from combination T4/T3 thyroid medication.

TPO Antibodies

Detects autoimmune thyroid disease (Hashimoto)
Thyroid Peroxidase (TPO) Antibodies target the TPO enzyme that is essential for thyroid hormone synthesis. Elevated TPO Antibodies indicate that the immune system is attacking the thyroid gland, a condition known as Hashimoto thyroiditis. This is the most common cause of hypothyroidism in developed countries and can be detected years before TSH becomes abnormal.
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Target < 35 IU/mL (negative)
Suggested Action Plan

If TPO Antibodies are elevated, you have autoimmune thyroiditis. Focus on reducing immune triggers: optimize vitamin D (50-80 ng/mL), address gut health (intestinal permeability), eliminate gluten if sensitive, manage stress, ensure adequate selenium (which has been shown to reduce TPO antibodies), and monitor thyroid function every 6-12 months.

Reverse T3

The thyroid brake that blocks active T3
Reverse T3 (rT3) is an inactive metabolite produced when T4 is converted by the type 3 deiodinase enzyme instead of the type 1 or 2 enzymes that produce active T3. Under conditions of chronic stress, illness, caloric restriction, or inflammation, the body preferentially produces rT3 to slow metabolism. Elevated rT3 can cause hypothyroid symptoms even when TSH and T4 are normal.
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Target < 15 ng/dL
Suggested Action Plan

If Reverse T3 is elevated, address the underlying cause: reduce chronic stress, treat infections or inflammation, ensure adequate caloric intake, optimize sleep, and correct nutrient deficiencies (selenium, iron, zinc). The Free T3 to Reverse T3 ratio should ideally be above 20.

Also in Hormonal

Hormone Imbalance

Explore by Biomarker

TSH Guide
Hashimoto's Thyroiditis
Free T3 Guide
Hypothyroidism

Getting Started

1
Get a Full Thyroid Panel

Do not accept TSH alone. Request TSH, Free T4, Free T3, TPO Antibodies, and Reverse T3. This complete panel reveals production, conversion, autoimmune, and metabolic stress issues that TSH alone cannot detect.

2
Optimize Thyroid Nutrients

Ensure adequate intake of selenium (200 mcg/day), zinc (30 mg/day), iron (ferritin 50-100 ng/mL), iodine (150 mcg/day), and vitamin D (50-80 ng/mL). These nutrients are essential for thyroid hormone production and conversion.

3
Address Root Causes

If TPO Antibodies are elevated, focus on gut health, gluten sensitivity, stress management, and immune modulation. If Reverse T3 is elevated, address chronic stress, sleep, and caloric adequacy. Treat the root cause, not just the numbers.

4
Monitor Regularly

Retest your full thyroid panel every 6-12 months, or every 6-8 weeks after medication adjustments. Track trends over time rather than relying on single snapshots.

Why I built this guide.

"Your thyroid controls your metabolism, energy, mood, and weight. A complete panel is essential for understanding what is really going on."

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