🦋 Thyroid — First Look
For everyone · 2 markers · $19.80
with code CAMERON $22.00
Fatigue, weight change, feeling cold, dry skin, or brain fog — and you want to know whether your thyroid is behind it before spending real money.
🩸 Order this exact panel — 10% off
All 2 markers load into your cart in one click. No doctor's visit, drawn at any Quest location in the US, results by email in about two weeks. Code CAMERON applies automatically.
Add all 2 markers — $19.80 → Open the full Bloodwork Vault →Why this panel
Thyroid disease is common, easy to miss, and reproduces the symptom list of a dozen other conditions. These two markers rule the common cases in or out.
What this panel can settle, and by what logic
Two tests, and everything they can do comes from reading them together rather than in turn.
- A raised TSH (Thyroid-Stimulating Hormone) with a low Free T4 (Thyroxine) is primary hypothyroidism. TSH moves against free T4 on a log-linear curve, so a small drop in circulating hormone produces a large and easily read rise in TSH — which is why the American Thyroid Association's review of thyroid function testing puts TSH first and free T4 beside it Van Uytfanghe 2023.
- A low TSH with a low free T4 points at the pituitary, not the thyroid. That single discordant pattern is the reason free T4 is worth the extra $9: it is the one result here that changes which organ gets investigated Van Uytfanghe 2023.
- A raised TSH with a normal free T4 is subclinical, which is a finding rather than a diagnosis. In pooled data from older adults a confirmed raised TSH still returned to normal untreated in 39.9% van der Spoel 2023, so this pattern buys a repeat draw, not a prescription.
- It settles the question of whether thyroid is worth pursuing at all. A normal TSH with a mid-range free T4 makes overt thyroid disease very unlikely, and the Whickham cohort's 20-year follow-up shows how much of the residual risk sits with antibodies rather than with the two numbers on this panel Razvi 2024.
What it cannot settle, and what would
It cannot tell you whether you have Hashimoto's disease. Autoimmune thyroiditis is the commonest cause of hypothyroidism in iodine-replete countries, and the test that shows it is thyroid peroxidase and thyroglobulin antibodies, which are not on this panel. Antibody status is what separates a TSH that will drift upward over years from one that will not Razvi 2024.
One TSH is not a thyroid diagnosis, because TSH is not one number. It has a genuine within-person set point and a diurnal swing, and the population interval it is judged against is far wider than any individual's own range van der Spoel 2021. The interval itself moves with age, iodine intake and assay Xing 2021.
It cannot explain a symptom by itself. Fatigue, weight change and low mood are the reasons people buy this test and are not specific to the thyroid; two normal results here mean the cause is elsewhere, which is a useful answer and not the one most buyers expect.
And it cannot recognize its own interference. A TSH that disagrees with the clinical picture is sometimes the assay rather than the patient — macro-TSH, heterophile antibodies and biotin all produce results that look real Al-Bahadili 2024. Macro-TSH is found by polyethylene glycol precipitation, which is a lab request, not another panel Piticchio 2024.
Draw conditions that decide whether the money is wasted
Three things decide whether these two numbers mean anything.
- Biotin is the expensive one, and it is in your hair supplement. At 5,000 to 10,000 mcg a day it competes in streptavidin-based immunoassays and pushes TSH and free T4 in opposite directions Li 2020 — a low TSH with a high free T4, which reads as hyperthyroidism in a person who does not have it. Stop it 72 hours before; that single instruction is worth more than the panel.
- Draw in the morning, and keep future draws at the same hour. TSH peaks overnight and falls through the day, so an afternoon value can run meaningfully below a morning one in the same person van der Spoel 2021. Comparing a 9am result against a 4pm result is how a stable thyroid looks like a changing one.
- Not during or just after an acute illness. Non-thyroidal illness suppresses TSH and then rebounds it above range during recovery Van Uytfanghe 2023, so a test taken in a bad fortnight measures the illness. Wait 4 to 6 weeks.
How you would know it answered your question, and what each pattern means next
Four patterns, and the retest interval each one earns.
- TSH (Thyroid-Stimulating Hormone) 4 to 10 mIU/L with a normal Free T4 (Thyroxine): repeat at 8 to 12 weeks and add Thyroid Antibodies (TPO + TgAb). Eight weeks is the pituitary's own re-equilibration time after any change in thyroid supply, so an earlier recheck reads the old set point — and a good share of these normalize on their own van der Spoel 2023.
- TSH above 10 mIU/L, or any TSH with a clearly low free T4: this is the result that goes to a clinician now rather than to another panel Van Uytfanghe 2023.
- Suppressed TSH with a high free T4: also a clinician, and before anything else confirm you were off biotin Li 2020.
- Both normal and you still feel unwell: the panel did its job. The next tests are Ferritin, Vitamin B12 and Free T3 (Triiodothyronine), not a second TSH — repeating a normal TSH in 6 weeks will return the same number for the same reason van der Spoel 2021.
Sources read for these sections
- Van Uytfanghe K, et al. Thyroid Stimulating Hormone and Thyroid Hormones (Triiodothyronine and Thyroxine): An American Thyroid Association-Commissioned Review of Current Clinical and Laboratory Status. Thyroid 2023 · PMID 37655789
- van der Spoel E, et al. Within-Person Variation in Serum Thyrotropin Concentrations: Main Sources, Potential Underlying Biological Mechanisms, and Clinical Implications. Frontiers in Endocrinology 2021 · PMID 33716972
- Xing D, et al. Factors influencing the reference interval of thyroid-stimulating hormone in healthy adults: A systematic review and meta-analysis. Clinical Endocrinology 2021 · PMID 33662155
- van der Spoel E, et al. Incidence and Determinants of Spontaneous Normalization of Subclinical Hypothyroidism in Older Adults. Journal of Clinical Endocrinology and Metabolism 2023 · PMID 37862463
- Li D, Ferguson A, Cervinski MA, Lynch KL, Kyle PB. AACC Guidance Document on Biotin Interference in Laboratory Tests. J Appl Lab Med 2020 · PMID 32445355
- Piticchio T, et al. PEG Precipitation to Detect Macro-TSH in Clinical Practice: A Systematic Review. Clinical Endocrinology 2024 · PMID 39702982
- Razvi SS, et al. Changes in Thyroid Function and Autoimmunity in Older Individuals: Longitudinal Analysis of the Whickham Cohort. Journal of Clinical Endocrinology and Metabolism 2024 · PMID 39673773
- Al-Bahadili H, et al. The Complex Web of Interferences with Thyroid Function Tests. Endocrine Practice 2024 · PMID 39477092
The 2 markers — and why each one is here
The screening marker — but indirect, and it misses people alone
What this panel is ordered to decide
A panel is a set of numbers until it settles something. These are the decisions this one feeds — each links the pathway it belongs to, what that pathway claims, and what its test list is read for.
The one pathway you should never guess at. Normal TSH with low free T3 and high reverse T3 is the classic dieting-induced conversion problem — the metabolic rate has dropped and no appetite suppressant addresses that. Equally: if thyroid is genuinely fine, this whole pathway is money spent on a problem you don't have.
TSH alone is not a thyroid panel. Normal TSH with low free T3 is impaired conversion, and it is the single most common thing missed in fatigue — you need the full set to see it.
Related panels
A panel gives you numbers. Skool is where they get read — 103 marker breakdowns with the optimal range rather than just the lab range, 42 evidence-graded protocols, and me answering questions daily. $10/mo, cancel anytime.
Join Skool — $10/mo →Frequently asked questions
2 markers: TSH (Thyroid-Stimulating Hormone), Free T4 (Free Thyroxine).
$22.00 before discount, $19.80 with code CAMERON applied automatically. Individual markers add a one-time $10 draw fee. Ordered through Marek Diagnostics and drawn at any Quest Diagnostics location in the US.
No. These are ordered direct-to-consumer through Marek Diagnostics — you order online, walk into a Quest location, and results are emailed to you in about two weeks. No physician visit or insurance required. Not available in NY, NJ or RI.
Morning. Stop biotin 72 hours before — it's in nearly every hair and nail supplement and it makes TSH read falsely low and T4 falsely high. This is the single most common cause of a bizarre thyroid result.
High TSH with normal free T4 is subclinical hypothyroidism — often monitored rather than treated. High TSH with low free T4 is overt and gets treated. Low TSH with high free T4 is hyperthyroid and needs a doctor promptly.
Where this goes next
The pages here are the frameworks. The protocols — the dosing, the order to correct things in, the week-by-week schedule and what to retest — are inside Skool.