Endocrinology and Metabolism

Original Article

Thyroid
Adequate Dose of Levothyroxine for Thyroid-Stimulating Hormone Suppression after Total Thyroidectomy in Patients with Differentiated Thyroid Cancer: Hyun Jin Ryu, Min Sun Choi, Hyunju Park, Tae Hyuk Kim, Jae Hoon Chung, So Young Park, Sun Wook Kim; Endocrinol Metab. 2024;39(4):615-621. Published online August 7, 2024; DOI: https://doi.org/10.3803/EnM.2023.1896

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Background
The adequate dose of levothyroxine (LT4) for patients who have undergone total thyroidectomy (TT) for differentiated thyroid cancer (DTC) is uncertain. We evaluated the LT4 dose required to achieve mild thyroid-stimulating hormone (TSH) suppression in DTC patients after TT.
Methods
The electronic medical records of patients who underwent TT for DTC and received mild TSH suppression therapy were reviewed. Linear regression analysis was performed to evaluate the association between LT4 dose (μg/kg) and an ordinal group divided by body mass index (BMI). We also evaluated the trend in LT4 doses among groups divided by BMI and age.
Results
In total, 123 patients achieved mild TSH suppression (0.1 to 0.5 mIU/L). The BMI variable was divided into three categories: <23 kg/m² (n=46), ≥23 and <25 kg/m² (n=30), and ≥25 kg/m² (n=47). In the linear regression analysis, BMI was negatively associated with the LT4 dose after adjusting for age and sex (P<0.001). The LT4 doses required to achieve mild TSH suppression based on the BMI categories were 1.86, 1.71, and 1.71 μg/kg, respectively (P for trend <0.001). Further analysis with groups divided by age and BMI revealed that a higher BMI was related to a lower LT4 dose, especially in younger patients aged 20 to 39 (P for trend=0.011).
Conclusion
The study results suggest an appropriate LT4 dose for mild TSH suppression after TT based on body weight in patients with DTC. Considering body weight, BMI, and age in estimating LT4 doses might help to achieve the target TSH level promptly.

Citations

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Levothyroxine Dosing for Thyroid-Stimulating Hormone Suppression in Patients with Differentiated Thyroid Cancer after Total Thyroidectomy
Mijin Kim
Endocrinology and Metabolism.2024; 39(4): 576. CrossRef

Review Article

Thyroid
Management of Subclinical Hypothyroidism: A Focus on Proven Health Effects in the 2023 Korean Thyroid Association Guidelines: Eu Jeong Ku, Won Sang Yoo, Hyun Kyung Chung; Endocrinol Metab. 2023;38(4):381-391. Published online August 8, 2023; DOI: https://doi.org/10.3803/EnM.2023.1778

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Abstract PDF PubReader ePub

Subclinical hypothyroidism (SCH) is characterized by elevated thyroid-stimulating hormone (TSH) and normal free thyroxine levels. The Korean Thyroid Association recently issued a guideline for managing SCH, which emphasizes Korean-specific TSH diagnostic criteria and highlights the health benefits of levothyroxine (LT4) treatment. A serum TSH level of 6.8 mIU/L is presented as the reference value for diagnosing SCH. SCH can be classified as mild (TSH 6.8 to 10.0 mIU/L) or severe (TSH >10.0 mIU/L), and patients can be categorized as adults (age <70 years) or elderly (age ≥70 years), depending on the health effects of LT4 treatment. An initial increase in serum TSH levels should be reassessed with a subsequent measurement, including a thyroid peroxidase antibody test, preferably 2 to 3 months after the initial assessment. While LT4 treatment is not generally recommended for mild SCH in adults, it is necessary for severe SCH in patients with underlying coronary artery disease or heart failure and it may be considered for those with concurrent dyslipidemia. Conversely, LT4 treatment is generally not recommended for elderly patients, regardless of SCH severity. For those SCH patients who are prescribed LT4 treatment, the dosage should be personalized, and serum TSH levels should be regularly monitored to maintain the optimal LT4 regimen.

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Original Articles

Clinical Study
Detection of Polyethylene Glycol Thyrotropin (TSH) Precipitable Percentage (Macro-TSH) in Patients with a History of Thyroid Cancer: Massimo Giusti, Lucia Conte, Anna Maria Repetto, Stefano Gay, Paola Marroni, Miranda Mittica, Michele Mussap; Endocrinol Metab. 2017;32(4):460-465. Published online December 14, 2017; DOI: https://doi.org/10.3803/EnM.2017.32.4.460

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Abstract PDF PubReader

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.

Citations

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PEG Precipitation to Detect Macro‐TSH in Clinical Practice: A Systematic Review
Tommaso Piticchio, Isabella Chiardi, Andrea Tumminia, Francesco Frasca, Mario Rotondi, Pierpaolo Trimboli
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Exploration of post-PEG precipitation TSH recovery in hypothyroid patients
Jing Yin, Zhanjun Mei, Bo Zhang, Fang Tang
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Prevalence and Pathogenesis of Macro-Thyrotropin in Neonates: Analysis of Umbilical Cord Blood from 939 Neonates and Their Mothers
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Falsely Elevated Thyroid Stimulating Hormone in Two Cases Requiring Special Follow-up
Serpil YANIK ÇOLAK, Eray ÖZGÜN, Burak ANDAÇ, Mine OKUR, Buket YILMAZ BÜLBÜL, Mehmet ÇELİK
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A comparative cross-sectional study on sleep quality in patients with a history of differentiated thyroid carcinoma and its correlation with quality of life
Marsida Teliti, Eleonora Monti, Martina Comina, Lucia Conte, Lara Vera, Stefano Gay, Giorgia Saccomani, Diego Ferone, Massimo Giusti
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A rare cause of subclinical hypothyroidism: macro-thyroid-stimulating hormone
Cem Onur Kirac, Sedat Abusoglu, Esra Paydas Hataysal, Aysegul Kebapcilar, Suleyman Hilmi Ipekci, Ali Ünlü, Levent Kebapcilar
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Neuroendocrine neoplasms – think about it and choose the most appropriate diagnostic and therapeutic steps
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Factors Influencing Peripheral Conversion of Thyroxine to Tri-Iodothyronine in Athyreotic Individuals during Levothyroxine Replacement.: Eui Young Kim, Won Gu Kim, Tae Yong Kim, Jong Ho Yoon, Suck Joon Hong, Young Kee Shong, Won Bae Kim; Endocrinol Metab. 2010;25(2):119-124. Published online June 1, 2010; DOI: https://doi.org/10.3803/EnM.2010.25.2.119

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Abstract PDF: BACKGROUND
Tri-iodothyronine (T3) is the main active hormone, and 20% of this is derived from the thyroid gland and 80% is from the peripheral tissue according to 5'-monodeiodination of thyroxine (T4). In the previous studies, normal T3 levels were achieved with traditional levothyroxine (LT4) therapy alone in athyreotic patients, but there has been no data about the factors influencing peripheral conversion of LT4. The aim of this study was to determine the factor(s) influencing peripheral conversion of LT4 to T3 in athyreotic patients during LT4 replacement. METHODS: The patients who underwent total-thyroidectomy for any cause, and mostly for thyroid cancers, at Asan Medical Center between 2000 and 2008 were enrolled. The free T4, T3 and thyroid stimulating hormone (TSH) levels and age, gender, weight, height, body mass index (BMI) and the T4 dose were measured. Only patients with normal ranges of free T4 and TSH were included in the analysis. RESULTS: A total of 143 patients were enrolled. The mean T3, free T4 and TSH levels were 143.7 ng/dL, 1.4 ng/dL and 1.6 microU/mL, respectively. The mean weight and BMI were 62.9 kg and 24.6 kg/m2, respectively. We divided them into two groups according to the serum T3 level and we compared the characteristics of the groups. There were no differences in age, the gender distribution, the T4 dose/weight and the BMI between the low T3 group (T3 < or = 122 ng/dL, n = 14) and the normal T3 group (T3 > 122 ng/dL, n = 129). In the low T3 group, the mean body weight was significantly lower than that of the normal T3 group (59.0 +/- 6.0 vs. 63.4 +/- 9.9, respectively, P = 0.025). CONCLUSION: Lean body mass seems to be an important factor for determining the peripheral conversion of T4 to T3 in human. This suggest that a combination of T3/T4 is better than T4 only when we treat the patients with hypothyroidism and who have a negligible amount of functioning thyroid tissue, if they have a low lean body mass.

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