A Complete Guide to Your Thyroid Panel
TSH, T3, T4, and thyroid antibodies—what they mean for your metabolism and energy
Medical Disclaimer
Thyroid disorders require proper diagnosis and medical management. This article is for educational purposes only. Always consult your healthcare provider before starting or changing thyroid treatment.
Why Your Thyroid is Critical
Your thyroid is a small butterfly-shaped gland in your neck, but its impact is massive. Thyroid hormones regulate metabolism, energy production, body temperature, heart rate, digestion, mood, and cognitive function.
When thyroid function is off—even slightly—every system in your body is affected. Yet thyroid dysfunction is remarkably common, affecting up to 20% of women and 10% of men, with many cases undiagnosed.
Key Thyroid Biomarkers
TSH (Thyroid-Stimulating Hormone)
What it is: Produced by the pituitary gland to signal the thyroid to produce more hormones.
Reference range: 0.4-4.0 mIU/L (varies by lab)
Optimal range: 1.0-2.0 mIU/L
- ⚠️High TSH (>2.5-4.0): Hypothyroidism (underactive thyroid)
- ⚠️Low TSH (<0.4): Hyperthyroidism (overactive thyroid)
The catch: TSH alone doesn't tell the full story. You can have "normal" TSH but low T3/T4, or subclinical hypothyroidism with symptoms but TSH just under the diagnostic threshold.
Free T4 (Thyroxine)
What it is: The main hormone produced by the thyroid. T4 is a prohormone that converts to T3 (the active form).
Reference range: 0.8-1.8 ng/dL
Why "Free": Only the unbound (free) T4 is biologically available. Total T4 includes bound hormone which is inactive.
Free T3 (Triiodothyronine)
What it is: The active thyroid hormone. T4 converts to T3 in peripheral tissues (liver, kidneys, gut).
Reference range: 2.3-4.2 pg/mL
Why it matters: T3 is 3-4 times more potent than T4. You can have adequate T4 but poor T4→T3 conversion due to stress, nutrient deficiencies (selenium, zinc), or inflammation.
Thyroid Antibodies
TPO (Thyroid Peroxidase Antibodies) & TgAb (Thyroglobulin Antibodies):
Detect Hashimoto's thyroiditis—an autoimmune condition where your immune system attacks the thyroid. It's the most common cause of hypothyroidism. Elevated antibodies indicate autoimmune thyroid disease, even if TSH is still normal.
Hypothyroidism: When Your Thyroid is Underactive
Common Symptoms
- •Fatigue and sluggishness
- •Weight gain despite normal eating
- •Cold intolerance
- •Dry skin, brittle nails, hair loss
- •Constipation
- •Brain fog, memory problems
- •Depression
- •Heavy or irregular periods
- •Elevated cholesterol
Treatment
Levothyroxine (T4): Synthetic T4 hormone. Most common treatment. Start low, titrate based on TSH.
Combination T4/T3 therapy: For patients who don't convert T4→T3 well and still have symptoms despite normalized TSH.
Desiccated thyroid: Animal-derived thyroid hormone containing T4 + T3. Less commonly used but preferred by some patients.
Hyperthyroidism: When Your Thyroid is Overactive
Common Symptoms
- •Weight loss despite increased appetite
- •Rapid or irregular heartbeat
- •Heat intolerance, excessive sweating
- •Nervousness, anxiety, irritability
- •Tremor (shaking hands)
- •Difficulty sleeping
- •Frequent bowel movements
- •Fatigue and muscle weakness
Common Causes & Treatment
Graves' disease: Autoimmune condition. Antibodies stimulate thyroid overproduction.
Treatment options: Anti-thyroid drugs (methimazole), radioactive iodine ablation, or surgery.
Supporting Thyroid Health
- •Iodine: Essential for thyroid hormone production. Found in iodized salt, seaweed, fish.
- •Selenium: Required for T4→T3 conversion. Brazil nuts are the richest source.
- •Zinc: Another cofactor for thyroid hormone synthesis.
- •Manage stress: Chronic cortisol elevation inhibits T4→T3 conversion.
- •Reduce inflammation: Inflammation impairs thyroid function.
- •Avoid goitrogens (in excess): Raw cruciferous vegetables, soy can interfere with thyroid function when consumed in large amounts.
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