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KMID : 1141520170320040460
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Endocrinology and Metabolism
2017 Volume.32 No. 4 p.460 ~ p.465
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Detection of Polyethylene Glycol Thyrotropin (TSH) Precipitable Percentage (Macro-TSH) in Patients with a History of Thyroid Cancer
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Giusti Massimo
Conte Lucia
Repetto Anna Maria
Gay Stefano
Marroni Paola
Mittica Miranda
Mussap Michele
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Abstract
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Background: Owing to its large molecular size, polyethylene glycol (PEG)-precipitable thyrotropin (TSH) can accumulate in the circulation, elevating TSH levels. PEG-precipitable TSH can be used to detect macro-TSH (mTSH) in serum. Our aim was to evaluate the prevalence of mTSH in patients who had undergone thyroidectomy for thyroid cancer.
Methods: Seventy-three thyroid cancer patients and 24 control subjects on levothyroxine (LT4) TSH-suppressive or replacement therapy were evaluated. Screening for mTSH was performed by adding PEG to serum in order to precipitate γ-globulin. A percentage of PEG-precipitable TSH ≥80% was considered suggestive of mTSH.
Results: No correlation between free-T4 (fT4) and TSH levels was found. PEG-precipitable TSH was 39.3%±1.9% in thyroid cancer patients and 44.1%±3.9% in controls. Macro-TSH was deemed to be present in one thyroid cancer patient and in two control subjects. Only in the thyroid cancer group was PEG-precipitable TSH found to be negatively correlated with fT4 concentration. No correlation was found between PEG-precipitable TSH and other clinical conditions in any patients.
Conclusion: The presence of mTSH seems to be a rare phenomenon in thyroid cancer. In some patients with low PEG-precipitable TSH, a reduction in LT4 dosage could be suggested. LT4 dosage adjusted to body weight is the main factor in maintaining TSH in a semi-suppressed or normal range. Evaluation of mTSH could be necessary in patients in whom a balance is required between adequate TSH suppression and the avoidance of unnecessary exogenous hyperthyroxinemia.
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KEYWORD
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Polyethylene glycol-precipitable thyrotropin, Macro-thyrotropin, Thyrotropin, Levothyroxine-posology, Thyroid neoplasms
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