Cited by 238Thyroid Disorders and TreatmentsPituitary Gland Disorders and TreatmentsGrowth Hormone and Insulin-like Growth Factors

The use of thyroid function tests in the diagnosis of hypopituitarism: definition and evaluation of the TSH Index

Jostel, Andreas, Ryder, W. David J., Shalet, Stephen M.·2009·Clinical Endocrinology

Abstract

Summary: Background TSH secretion in hypopituitary patients may be decreased due to TSH deficiency but it also remains under feedback inhibition by free thyroxine (fT4). We propose a TSH index (TSHI), as ‘fT4‐adjusted TSH’, that corrects for any physiological TSH suppression, to provide a true estimate of pituitary thyrotroph function and any pathological pituitary suppression. Methods A total of 9519 thyroid function tests (TFTs) (Bayer Immuno‐1 ® ) in 4064 patients of our institution were examined, including 444 patients investigated for hypopituitarism. Based on the physiological log‐linear relationship between fT4 and TSH, we estimated the amount of feedback‐induced change in log TSH per change in fT4, which allowed the extrapolation of log TSH to a fixed fT4 of 0, defining the TSHI. TSHIs were compared with other measures of pituitary function. Results Feedback inhibition was estimated to cause a 0·1345 decrease in log TSH (mU/l) for 1 pmol/l increase in fT4 concentration, therefore TSHI = log TSH + 0·1345 × fT4. Patients with lower peak‐stimulated GH and cortisol concentrations had a significantly lower TSHI ( P < 0·0001). TSHIs measured before pituitary stimulation tests predicted highly significantly the risk of test failure ( P = 0·0002). Of all potential fT4–TSH combinations within the current reference ranges, 21·9% were identified as abnormal on the basis of the TSHI. Conclusion The TSHI provides an accurate estimate of the severity of pituitary dysfunction in hypopituitary patients based on simple TFTs. It predicts the probability of pituitary stimulation test failure and extends the diagnosis of TSH deficiency into areas of the normal TFT reference ranges.

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Crossref · 10.1111/j.1365-2265.2009.03534.x

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Authors
Jostel, A., Ryder, W. D. J., & Shalet, S. M.
Affiliations
The Christie Hospital (GB)
Corresponding author
Jostel, Andreas
Venue
Clinical Endocrinology
Publisher
Wiley
Published
2009-09-07
Volume
71
Issue
4
Pages
529-534
ISSN
  • 0300-0664 (ISSN-L)
  • 1365-2265
OpenAlex
W2096162365
Cited by
238
References
16
Citations by year
2026: 24 · 2025: 39 · 2024: 36 · 2023: 28 · 2022: 24 · 2021: 17 · 2020: 13 · 2019: 14 · 2018: 11 · 2017: 3 · 2016: 8 · 2015: 4 · 2014: 6 · 2013: 3 · 2012: 4
FWCI
1.69
Type
journal article
Language
en
Open access
closed
Locations
  • Clinical Endocrinology (publishedVersion)
  • PubMed (publishedVersion)
Topics
  • Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Thyroid Disorders and Treatments
  • Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Pituitary Gland Disorders and Treatments
  • Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Growth Hormone and Insulin-like Growth Factors
Keywords
hypopituitarism, thyroid-stimulating hormone, TSH deficiency, free thyroxine, growth hormone, cortisol, thyroid function tests
MeSH terms
Adult, Aged, Aged, 80 and over, Female, Humans, Hypopituitarism, Male, Middle Aged, Reference Values, Thyroid Function Tests, Thyrotropin, Thyroxine, Thyrotrophs

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