TSH Index (TSHI) of Jostel et al for Identifying a Patient with Hypopituitarism

This index can help to identify a patient with hypopituitarism whose TSH and free T4 are still within the normal reference range.

Parameters:

(1) free T4 in pmol/L

(2) TSH in mU/L

TSHI =

= LN(TSH) + (0.1345 * (free T4))

According to Figure 4, the line for TSHI that is -1.96 SD below the mean is:

LN(TSH) =

= (-0.1353 * (free T4)) + 1.3676

If this is rearranged:

LN(TSH) + (0.1353 * (free T4)) = 1.3676

TSH deficiency was defined as a result with the following features:

(1) LN(TSH) below the line

(2) free T4 above lower limit of normal reference range (9 pmol/L)

(3) TSH above the lower limit of normal reference range (0.35 mU/L)

Limitations:

• The equation requires assays for TSH and free T4 with similar performance characteristics.