Assessment of Thyroid Function

Martin I. Surks

doi:10.1016/S0161-6420(81)35000-3

Assessment of Thyroid Function

Martin I. Surks

Medicine

Research output: Contribution to journal › Article › peer-review

4 Scopus citations

Abstract

The thyroid hormones Thyroxine (T₄) and Triiodothyronine (T₃) can be measured directly in serum by radioimmunoassay. Most serum T₄ and T₃ circulates bound to specific serum-binding proteins but, the small unbound fraction, free T₄, correlates best with hormonal activity. The free T₄ concentration can be measured directly and also can be estimated from the T₃ resin uptake as the free T₄ index (FT₄-1). In hypothyroidism, T₄ and FT₄-1 are decreased and when the disorder results from thyroid gland failure, serum TSH will be elevated as well. Indeed, an increase in serum TSH is the most sensitive index of thyroid gland failure. Hyperthyroidism is associated with increased serum T₄, T₃, and free T₄. About 5% of patients have a selective increase in T₃ secretion: T₃ thyrotoxicosis. In these, serum T₄ is normal but serum T₃ is elevated. An absent TSH response to thyrotropin-releasing hormone (TRH) is the hallmark of hyperthyroidism due to suppression of anterior pituitary TSH secretion.

Original language	English (US)
Pages (from-to)	476-478
Number of pages	3
Journal	Ophthalmology
Volume	88
Issue number	6
DOIs	https://doi.org/10.1016/S0161-6420(81)35000-3
State	Published - 1981

Keywords

free T
hyperthyroidism
hypothyroidism
serum thyrotropin (TSH)
thyroid
thyrotropin-releas ing hormone (TRH)
thyroxine (T)
triidothyronine (T)

ASJC Scopus subject areas

Ophthalmology

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10.1016/S0161-6420(81)35000-3

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title = "Assessment of Thyroid Function",

abstract = "The thyroid hormones Thyroxine (T4) and Triiodothyronine (T3) can be measured directly in serum by radioimmunoassay. Most serum T4 and T3 circulates bound to specific serum-binding proteins but, the small unbound fraction, free T4, correlates best with hormonal activity. The free T4 concentration can be measured directly and also can be estimated from the T3 resin uptake as the free T4 index (FT4-1). In hypothyroidism, T4 and FT4-1 are decreased and when the disorder results from thyroid gland failure, serum TSH will be elevated as well. Indeed, an increase in serum TSH is the most sensitive index of thyroid gland failure. Hyperthyroidism is associated with increased serum T4, T3, and free T4. About 5% of patients have a selective increase in T3 secretion: T3 thyrotoxicosis. In these, serum T4 is normal but serum T3 is elevated. An absent TSH response to thyrotropin-releasing hormone (TRH) is the hallmark of hyperthyroidism due to suppression of anterior pituitary TSH secretion.",

keywords = "free T, hyperthyroidism, hypothyroidism, serum thyrotropin (TSH), thyroid, thyrotropin-releas ing hormone (TRH), thyroxine (T), triidothyronine (T)",

author = "Surks, {Martin I.}",

note = "Funding Information: Supported by NIH Grants CA 24604-02 and CA 16463-06.",

year = "1981",

doi = "10.1016/S0161-6420(81)35000-3",

language = "English (US)",

volume = "88",

pages = "476--478",

journal = "Ophthalmology",

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PY - 1981

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N2 - The thyroid hormones Thyroxine (T4) and Triiodothyronine (T3) can be measured directly in serum by radioimmunoassay. Most serum T4 and T3 circulates bound to specific serum-binding proteins but, the small unbound fraction, free T4, correlates best with hormonal activity. The free T4 concentration can be measured directly and also can be estimated from the T3 resin uptake as the free T4 index (FT4-1). In hypothyroidism, T4 and FT4-1 are decreased and when the disorder results from thyroid gland failure, serum TSH will be elevated as well. Indeed, an increase in serum TSH is the most sensitive index of thyroid gland failure. Hyperthyroidism is associated with increased serum T4, T3, and free T4. About 5% of patients have a selective increase in T3 secretion: T3 thyrotoxicosis. In these, serum T4 is normal but serum T3 is elevated. An absent TSH response to thyrotropin-releasing hormone (TRH) is the hallmark of hyperthyroidism due to suppression of anterior pituitary TSH secretion.

AB - The thyroid hormones Thyroxine (T4) and Triiodothyronine (T3) can be measured directly in serum by radioimmunoassay. Most serum T4 and T3 circulates bound to specific serum-binding proteins but, the small unbound fraction, free T4, correlates best with hormonal activity. The free T4 concentration can be measured directly and also can be estimated from the T3 resin uptake as the free T4 index (FT4-1). In hypothyroidism, T4 and FT4-1 are decreased and when the disorder results from thyroid gland failure, serum TSH will be elevated as well. Indeed, an increase in serum TSH is the most sensitive index of thyroid gland failure. Hyperthyroidism is associated with increased serum T4, T3, and free T4. About 5% of patients have a selective increase in T3 secretion: T3 thyrotoxicosis. In these, serum T4 is normal but serum T3 is elevated. An absent TSH response to thyrotropin-releasing hormone (TRH) is the hallmark of hyperthyroidism due to suppression of anterior pituitary TSH secretion.

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KW - serum thyrotropin (TSH)

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KW - thyrotropin-releas ing hormone (TRH)

KW - thyroxine (T)

KW - triidothyronine (T)

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Assessment of Thyroid Function

Abstract

Keywords

ASJC Scopus subject areas

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