Jostel’s TSH Index (TSHI / sTSHI)
Jostel's TSH index (Jostel 2009): ln(TSH) + 0.1345 × free T4, with a standardized sTSHI; a low index suggests central (secondary) hypothyroidism.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- TSH
- 1.5 mU/L
- Free T4
- 15 pmol/L
Result: TSH index 2.42 (sTSHI -0.41) — within/above the reference band (TSHI ~1.3–4.1).
The tool opens with these values already filled in. Replace them with your own.
What the result means
- Reference
- TSHI ~1.3–4.1, sTSHI −2 to +2; a low index suggests central (secondary) hypothyroidism.
What you enter
- TSH
- Free T4
How this is calculated
- Formula
- TSHI = ln(TSH) + 0.1345 × FT4 (pmol/L); standardized sTSHI = (TSHI − 2.7) / 0.676.
Jostel A, Ryder WD, Shalet SM. The use of thyroid function tests in the diagnosis of hypopituitarism: definition and evaluation of the TSH index. Clin Endocrinol (Oxf). 2009;71(4):529-534. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.