Detection of Polyethylene Glycol Thyrotropin (TSH) Precipitable Percentage (Macro-TSH) in Patients with a History of Thyroid Cancer.
10.3803/EnM.2017.32.4.460
- Author:
Massimo GIUSTI
1
;
Lucia CONTE
;
Anna Maria REPETTO
;
Stefano GAY
;
Paola MARRONI
;
Miranda MITTICA
;
Michele MUSSAP
Author Information
1. Department of Internal Medicine, University of Genoa, Genoa, Italy. magius@unige.it
- Publication Type:Original Article
- Keywords:
Polyethylene glycol-precipitable thyrotropin;
Macro-thyrotropin;
Thyrotropin;
Levothyroxine-posology;
Thyroid neoplasms
- MeSH:
Body Weight;
Humans;
Hyperthyroxinemia;
Mass Screening;
Polyethylene Glycols*;
Polyethylene*;
Prevalence;
Reference Values;
Thyroid Gland*;
Thyroid Neoplasms*;
Thyroidectomy;
Thyrotropin*;
Thyroxine
- From:Endocrinology and Metabolism
2017;32(4):460-465
- CountryRepublic of Korea
- Language:English
-
Abstract:
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.
