What this test measures
The neonatal thyroid screen (often labelled NEOT or simply "neonatal TSH / T4") measures thyroid-stimulating hormone (TSH) and / or total thyroxine (T4) in a small blood sample from the newborn, typically drawn from a heel prick onto a dried blood spot (DBS) card 48–72 hours after birth (or a venous sample if needed).
It is the standard first-tier test in newborn screening for congenital hypothyroidism (CH). Most programmes use TSH as the primary marker; some use T4 with TSH reflex. Abnormal screening results trigger confirmatory venous testing within days, and treatment is started immediately if confirmed.
Why it matters
Congenital hypothyroidism affects about 1 in 1100 newborns in India (slightly higher than the global average of 1 in 2000–3000). Untreated, it causes severe and irreversible intellectual disability, growth failure and developmental delay. The condition is silent in the first weeks of life — clinical signs are subtle or absent, so universal newborn screening is the only way to detect it early.
The Indian Academy of Paediatrics and the Government of India's Rashtriya Bal Swasthya Karyakram (RBSK) recommend universal newborn thyroid screening. When CH is detected and treatment with levothyroxine started before 2–3 weeks of age, outcomes are normal — most affected children grow up with normal intelligence and development. Delay beyond 4–6 weeks causes irreversible cognitive loss.
How to prepare
No preparation needed. The sample is usually collected as a heel-prick dried blood spot between 48 and 72 hours of life (and not earlier than 24 hours — the physiological TSH surge after birth can give false positives). Mention if the baby is premature, sick, on any medication, has received recent transfusion, or has a family history of thyroid disease.
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| TSH (Neonatal Screen) (mIU/L)[1][2] | Screen cut-off typically < 20 (DBS) · Venous confirmatory < 10 by day 7 | Low TSH is uncommon — can suggest central (pituitary) hypothyroidism, which screen-based TSH testing alone may miss (a screening programme that uses T4 will catch this). | Raised TSH on screening (>20 mIU/L on DBS) — needs urgent confirmatory venous TSH and free T4. If confirmed (elevated TSH + low free T4) — start levothyroxine immediately. Mildly raised TSH with normal T4 may reflect transient neonatal hyperthyrotropinaemia, iodine deficiency, or maternal antithyroid drug exposure — follow up by the paediatric endocrinology team. |
| Total T4 (when included) (µg/dL) | Day 3 venous total T4 9 – 22 (age-dependent) | Low T4 with raised TSH — primary hypothyroidism — start levothyroxine. Low T4 with low or normal TSH — central (pituitary) hypothyroidism — needs MRI brain and other pituitary hormone evaluation. | High T4 in newborns is uncommon — can reflect neonatal Graves' disease (maternal autoimmune transfer), TBG excess, or congenital thyrotoxicosis. |
Neonatal thyroid screen — actions by result
| Result | Interpretation | Action |
|---|---|---|
| TSH < 20 mIU/L (DBS) | Normal | No further testing |
| TSH 20 – 40 mIU/L | Borderline / possibly raised | Repeat venous TSH + free T4 within 7 days |
| TSH > 40 mIU/L | High suspicion of congenital hypothyroidism | Urgent venous TSH + free T4; start levothyroxine immediately if confirmed |
| Low T4 + normal/low TSH | Suspected central hypothyroidism | Pituitary workup + MRI brain |
| Premature / low birth weight | Risk of transient hypothyroxinaemia | Repeat in 2–4 weeks; treat if persistent |
Frequently asked questions
When should the neonatal thyroid screen be done?
Ideally between 48 and 72 hours of life (after the physiological TSH surge has settled). Earlier sampling (especially before 24 hours) can give false positives. Some programmes test by 7 days of life if early sampling was missed.
How is the sample collected?
A small heel-prick blood drop placed on filter paper (a dried blood spot or "Guthrie" card) — the standard newborn screening method worldwide. A venous sample can be used if needed.
Why screen if my baby looks healthy?
Congenital hypothyroidism is silent in the first weeks — clinical signs (prolonged jaundice, lethargy, feeding problems, constipation, coarse cry) appear later, often after irreversible brain damage has begun. Screening catches it before damage occurs.
My baby's screen was abnormal. Is it definitely hypothyroidism?
Not necessarily. A raised screening TSH needs confirmation with a venous sample. Causes of transient elevation include prematurity, maternal antithyroid drug exposure, iodine excess or deficiency. Even so, do not delay — confirmatory testing must be done urgently.
What is the treatment for congenital hypothyroidism?
Levothyroxine, started as soon as possible — ideally within 2 weeks of birth. The dose is age- and weight-adjusted (typically 10–15 µg/kg/day initially) and monitored monthly initially, then less frequently. Treatment is usually lifelong, though some cases of transient CH can be reassessed at 3 years.
Can a premature baby have a normal screen?
Premature babies have immature hypothalamic-pituitary-thyroid axes and may show delayed TSH rise. A repeat screen at 2–4 weeks is recommended in babies born before 34 weeks or with very low birth weight.
Does this test screen for anything else?
In some Indian programmes, the same dried blood spot also tests for congenital adrenal hyperplasia, G6PD deficiency, sickle cell disease and inborn errors of metabolism (depending on the panel). Ask your hospital or paediatrician which conditions are included.
Related Other / Biochemistry tests
Tests commonly ordered alongside NEOT, or that help interpret an unexpected result.
Sources & references
- Indian Academy of Pediatrics — Newborn Screening Guidelines · accessed 2026-05-30T00:00:00.000Z
- NCBI StatPearls — Congenital Hypothyroidism · accessed 2026-05-30T00:00:00.000Z
- American Academy of Pediatrics — Update of Newborn Screening for Congenital Hypothyroidism · accessed 2026-05-30T00:00:00.000Z
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