mathematics

Jostel's TSH index

Jostel's TSH index is a mathematics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Jostel's TSH index rather than just read about it. In short: Jostel's TSH index (TSHI or JTI), also referred to as Jostel's thyrotropin index or Thyroid Function index (TFI), is a method for estimating the thyrotropic (i.e. thyroid stimulating) function of the anterior pituitary lobe in a quantitative way. The equation has been derived from the logarithmic standard model of thyroid homeostasis.

Key takeaways

Jostel's TSH index belongs to mathematics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Jostel's TSH index to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Jostel's TSH index from memory before moving on to harder problems.

Reference excerpt

Jostel's TSH index (TSHI or JTI), also referred to as Jostel's thyrotropin index or Thyroid Function index (TFI), is a method for estimating the thyrotropic (i.e. thyroid stimulating) function of the anterior pituitary lobe in a quantitative way. The equation has been derived from the logarithmic standard model of thyroid homeostasis. In a paper from 2014 further study was suggested to show if it is useful, but the 2018 guideline by the European Thyroid Association for the diagnosis of uncertain cases of central hypothyroidism regarded it as beneficial. It is also recommended for purposes of differential diagnosis in the sociomedical expert assessment.

How to determine JTI Jostel's TSH index can be calculated with

T S H I = ln ⁡ ( T S H ) + 0.1345 ⋅ F T 4 {\displaystyle TSHI=\ln(TSH)+0.1345\cdot FT4}

from equilibrium serum concentrations of thyrotropin (TSH), free T4 (FT4) and a correction coefficient derived from the logarithmic standard model (β = 0.1345). An alternative standardised form (standardised TSH index or sTSHI) is calculated with.

s T S H I = T S H I − 2.7 0.676 {\displaystyle sTSHI={\frac {TSHI-2.7}{0.676}}}

as a z-transformed value incorporating mean (2.7) and standard deviation (0.676) of TSHI in a reference population

Reference ranges

Clinical significance The TSH index is reduced in patients with secondary hypothyroidism resulting from thyrotropic insufficiency. For this indication, it has, however, up to now only been validated in adults. JTI was also found reduced in cases of TACITUS syndrome (non-thyroidal illness syndrome) as an example of type 1 thyroid allostasis. Conversely, an elevated thyroid function index may serve as a biomarker for type 2 allostasis and contextual stress. Jostel's TSH index may decrease under therapy with the antidiabetic drug metformin, especially in women under oral contraceptives. In patients undergoing thyroidectomy for thyroid nodules, the TSH index was significantly elevated in cases of cancer compared to cases of benign nodules. In two large population-based cohorts included in the Study of Health in Pomerania differentially correlated to some markers of body composition. Correlation was positive to body mass index (BMI), waist circumference and fat mass, but negative to body cell mass. With the exception of fat mass all correlations were age-dependent. Very similar observations have been made earlier in the NHANES dataset. In Parkinson's disease, JTI is significantly elevated in early sub-types of the disease compared to an advanced group. A longitudinal study in euthyroid subjects with structural heart disease found that JTI predicts the risk of malignant arrhythmia including ventricular fibrillation and ventricular tachycardia. This applies to both incidence and event-free survival. A second study in a different population undergoing coronary angiography arrived at similar results. It was therefore concluded that an elevated set point of thyroid homeostasis may contribute to cardiovascular risk. A positive correlation of JTI to SIQALS 2, a score for allostatic load, suggests that thyroid hormones are among the mediators linking stress to major cardiovascular endpoints. Jostel's TSH index and the thyroid feedback quantile-based index, another biomarker for the central thyrotropic function, were observed to be elevated in certain psychiatric diseases including schizophrenia. Another study demonstrated the TSH index to inversely correlate to thyroid's secretory capacity and thyroid volume. It is unclear if this finding reflects shortcomings of the index (i.e. low specificity in the setting of subclinical hypothyroidism) or plastic responses of the pituitary gland to beginning hypothyroidism. In subjects with type 2 diabetes, treatment with beta blockers resulted in increased TSH index, but the mechanism is unclear. Negative correlation of Jostel's TSH index to the urinary excretion of certain phthalates suggests that endocrine disruptors may affect the central set point of thyroid homeostasis. Drugs that reduce the TSH index, probably via effects on the central set point of the feedback loop, include mirtazapine and oxcarbazepine. A reduction of Jostel's TSH index may predict the development of hypophysitis due to therapy with immune checkpoint inhibitors, e. g. ipilimumab.

See also Thyroid function tests Thyrotroph Thyroid Hormone Sensitivity Index Thyroid's secretory capacity Sum activity of peripheral deiodinases Thyroid Feedback Quantile-based Index

References

External links SPINA Thyr: Open source software for TSHI Package "SPINA" for the statistical environment R

Illustrations

Worked examples

Example 1 — a first encounter with Jostel's TSH index

Start with the simplest possible case. Write down what Jostel's TSH index claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In mathematics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Jostel's TSH index before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Jostel's TSH index ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Jostel's TSH index

In research: Jostel's TSH index appears in mathematics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Jostel's TSH index in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Jostel's TSH index is common in secondary-school and first-year university syllabi. It links to neighbouring topics Blood tests, Clinical chemistry, Endocrine procedures, so understanding it makes those chapters shorter.
In everyday life: Look for Jostel's TSH index outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Jostel's TSH index in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Jostel's TSH index means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Jostel's TSH index out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Jostel's TSH index in simple terms?

Why does Jostel's TSH index matter?

Because it connects several mathematics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Jostel's TSH index?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Jostel's TSH index.