The thyroid gland produces two hormones: thyroxine (T4) and triiodothyronine (T3). These hormones regulate the way the body uses energy (metabolism). Thyroid testing is highly recommended for newborns/children to make sure that the gland works normally as any problem could impair growth and development. Also the tests are used to check how successful the treatment of thyroid disease is.

Sample requirement

A blood sample is required to perform the tests. It is a simple process with only a momentary slight pain from the needle stick.

Method of test used

  • Total Thyroxine (T4)
  • Free Thyroxine (FT4)
  • Free Thyroxine Index (FTI)
  • Total Triiodothyronine (T3)
  • Free Triiodothyronine (FT3)
  • Thyroid-Stimulating Hormone (TSH)

Result parameters

Total Thyroxine (T4)

Adults:5.4–11.5 micrograms per deciliter (mcg/dL) / nanomoles per liter (57–148 nmol/L)

Babies/Children:6.4–13.3 mcg/dL (83–172 nmol/L)

Newborn: 11.8–22.6 mcg/dL (152–292 nmol/L)

Free Thyroxine (FT4)

0.7–2.0 ng/dL nanograms per deciliter (ng/dL) / 10–26 picomoles per liter (pmol/L)

Free Thyroxine Index (FTI): 1.5-4.5

Total Triiodothyronine (T3)

Adults: 80–200 ng/dL (1.2–3.1 nmol/L)

Adolescents (12-23): 82–213 ng/dL (1.3–3.28 nmol/L)

Children (1-11): 105–245 ng/dL (1.6–3.8 nmol/L)

Free Triiodothyronine (FT3)

Adults: 260–480 picograms per deciliter (pg/dL) or 4.0–7.4 pmol/L

Thyroid-Stimulating Hormone (TSH)

Adults: 0.4–4.2 microunits per milliliter (mcU/mL) or 0.4–4.2 milliunits per liter (mU/L)

Children: 0.7–6.4 mcU/mL or 0.7–6.4 mU/L

Newborn: 1–39 mcU/mL or 1–39 mU/L