Thyroid Panel
TSH alone isn’t enough. Your thyroid panel should include TSH, Free T3, and Free T4 together — otherwise you might miss a problem that’s making you tired, cold, and gaining weight.
Your thyroid controls your metabolism, energy, and body temperature. TSH tells you how hard your brain is pushing the thyroid. Free T4 is the storage hormone. Free T3 is the active hormone that actually does the work. You need all three to see the full picture.
What is the thyroid panel?
Your thyroid is a small gland in your neck that controls how fast your metabolism runs. The full panel measures three things:
- TSH — a signal from your brain telling the thyroid how hard to work. High TSH means your brain is screaming at a sluggish thyroid.
- Free T4 — the storage hormone your thyroid makes. Needs to be converted to T3 to actually work.
- Free T3 — the active hormone. This is what enters your cells and drives your metabolism, body temperature, and energy.
The problem with testing only TSH: it can look "normal" while your Free T3 is actually low — because the conversion of T4 to T3 is broken. This is especially common in India due to widespread selenium deficiency.
What your number means
| Marker | Lab range | Longevity optimal |
|---|---|---|
| TSH | 0.5–4.5 mIU/L | 1.0–2.5 mIU/L |
| Free T4 | 0.8–1.8 ng/dL | 1.1–1.6 ng/dL (mid-upper) |
| Free T3 | 2.0–4.4 pg/mL | 3.2–4.4 pg/mL (upper half) |
How to improve it
The enzymes that convert T4 to active T3 are selenium-dependent. Selenium deficiency — common in India — impairs this conversion, leaving you with normal TSH and T4 but low T3 (and symptoms like fatigue, weight gain, and brain fog).
Selenium 100–200 mcg/day (selenomethionine) can meaningfully improve T4→T3 conversion. In Hashimoto’s patients, it also reduces TPO antibody levels. Don’t exceed 400 mcg/day.
Want to track your thyroid panel?
eterni tracks TSH, Free T3, and Free T4 together over time — so you can see if your selenium protocol is actually improving conversion.
Get early accessFrequently Asked Questions
Is TSH alone enough to check thyroid health?
No. TSH is a signal from your brain, not a measure of actual thyroid hormones. It can look normal while Free T3 (the active hormone) is low due to poor conversion. Always test TSH + Free T3 + Free T4 together.
What is subclinical hypothyroidism?
Mildly elevated TSH (4.5–10 mIU/L) with normal Free T3 and T4. Your thyroid is struggling so your brain pushes harder. Symptoms often still occur — fatigue, weight gain, cold intolerance. Affects 10–15% of Indian adults.
Does selenium help thyroid function?
Yes — the enzymes that convert T4 to active T3 need selenium. Deficiency (common in India due to selenium-poor soils) impairs conversion. 100–200 mcg/day selenomethionine can improve T3 levels and reduce Hashimoto’s antibodies.
Hashimoto’s in India
Hashimoto’s autoimmune thyroiditis is the most common cause of hypothyroidism in India. The immune system attacks thyroid tissue, progressively reducing function. Diagnosis requires TPO antibody testing. High-dose iodine can worsen Hashimoto’s — stick to 150 mcg/day from food and supplements combined. Selenium is the preferred supplement.
Clinical vs optimal TSH
Many doctors consider TSH up to 4.5 mIU/L "normal." Longevity medicine targets 1.0–2.5 mIU/L. The difference matters — a TSH of 3.5 with symptoms like fatigue and weight gain may warrant investigation, even though it’s technically "in range."
The low-T3 pattern
Normal TSH + normal Free T4 + low Free T3 = impaired peripheral conversion. This pattern is only visible when you test all three markers. Selenium supplementation, stress reduction, and addressing inflammation all improve T4→T3 conversion.
Connected supplements
Selenium (selenomethionine 100–200 mcg/day) is the primary intervention. Iodine (150 mcg/day — not more) supports thyroid hormone production. Zinc supports thyroid hormone synthesis. Ashwagandha can raise T3 and T4 in hypothyroid individuals — use with caution on thyroid medication.
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eterni connects your lab results, supplements, and retests — so you can see the trajectory, not just a snapshot.
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