Age influences TSH serum levels after withdrawal of l-thyroxine or rhTSH stimulation in patients affected by differentiated thyroid cancer

Rebound effect of hypothalamic-pituitary thyreotropic activity: a new model to better understand hypothyroidism

PURPOSE

Hypothalamic-pituitary thyrotropic activity (HPta) is crucial since TSH is the mainstay for evaluating primary hypothyroidism (hT) and replacement therapy in clinical practice. Despite TSH values, some patients experience symptoms and metabolic alterations, raising several issues about hT. The aim of the study was to investigate factors influencing the TSH values achieved after a period of hT induced in a standardized and controlled manner (TSH_time1).

METHODS

Our institutional database was searched to extract records of differentiated thyroid cancer (DTC) patients undergoing a LT4 withdrawal protocol prior to radioiodine (RAI) administration. We collected clinical and biochemical parameters before LT4 discontinuation and after one month of induced hT. We performed Mann-Whitney U-test and linear regression analyses.

RESULTS

We included 102 patients, with a median age of 44 years. In univariate analyses, TSH_time1 was correlated with age (p 0.005) and the dose pro Kg/die of LT4 assumed until the discontinuation of LT4 (LT4_dose) (p 0.023). The higher the age, the lower the TSH_time1 level. The higher the LT4_dose, the higher the TSH_time1 level. After multivariate analysis, the fittest model included age, BMI, LT4_dose, and systemic inflammation response index with an adjusted R2 of 0.4.

CONCLUSION

The study highlights new mechanisms that influence HPta. HPta progressively reduces with age, and this must be considered when evaluating TSH values in the elderly. Furthermore, we report for the first time a rebound effect of HPta, determined by the dose pro Kg/die of LT4 taken prior to its discontinuation. Inflammation and metabolic status also affect these phenomena.

Type 2 Deiodinase Thr92Ala Polymorphism and Aging Are Associated with a Decreased Pituitary Sensitivity to Thyroid Hormone

Background: The DIO2 Thr92Ala polymorphism (rs225014), which occurs in about 15-30% of Caucasian people, determines a less efficient type 2 deiodinase (D2) enzyme. The aim of this study was to determine the impact of DIO2 Thr92Ala polymorphism on the serum thyrotropin (TSH) levels in thyroidectomized patients with hypothyroidism and to evaluate whether TSH levels and aging could be related, at pituitary level, to D2 activity. Methods: This prospective study was performed on 145 thyroid cancer patients, treated with total thyroidectomy, and undergoing radioiodine treatment after 3 weeks of levothyroxine (LT4) withdrawal. A mouse model has been used to determine D2 protein and mRNA levels in pituitary during aging. Results: Genetic analysis identified DIO2 Thr92Ala polymorphism in 56% of participants: 64/145 (44%) patients were homozygous wild type (WT) (Thr/Thr), 64 (44%) heterozygous (Thr/Ala), and 17 (12%) homozygous mutant (Ala/Ala). A significant negative relationship was observed between aging and the rise in serum TSH levels during LT4 withdrawal. However, this negative correlation found in WT was reduced in heterozygous and lost in mutant homozygous patients (Thr/Thr r = -0.45, p = 0.0002, 95% confidence interval [CI] -0.63 to -0.23; Ala/Thr r = -0.39, p = 0.0012, CI -0.60 to -0.67; and Ala/Ala r = -0.30, p = 0.2347; CI -0.70 to 0.20). Accordingly, when we compared the TSH measured in each patient to its theoretical value predicted from age, the TSH did not reach its putative target in 47% of WT patients, in 70% of Ala/Thr, and 76% of Ala/Ala carrying patients (p = 0.0036). This difference was lost in individuals older than 60 years, suggesting a decline of D2 associated with aging. The hypothesis that the pituitary D2 decreases with age was confirmed by the evidence that D2 mRNA and protein levels were lower in pituitary from old versus young mice. Conclusion: An age-related decline in TSH production in response to hypothyroidism was correlated with decreased D2 levels in pituitary. The presence of DIO2 homozygous Ala/Ala polymorphism was associated with a reduced level of TSH secretion in response to hypothyroidism, indicating a decreased pituitary sensitivity to serum thyroxine variation (Institutional Research Ethics board approval number no. 433/21).

IS IT WORTH SUPPRESSING TSH IN LOW- AND INTERMEDIATE-RISK PAPILLARY THYROID CANCER PATIENTS BEFORE THE FIRST DISEASE ASSESSMENT?

OBJECTIVE

Guidelines recommend thyroid-stimulating hormone (TSH) suppression before the first response to treatment assessment in papillary thyroid cancer (PTC) patients. The aim of this study was to assess the rate of structural disease (SD) in low- and intermediate-risk PTC patients according to TSH levels measured 1 year after primary treatment.

METHODS

A consecutive, prospective series of low- and intermediate-risk PTC patients with 3-years follow-up was collected. TSH, thyroglobulin (Tg), antithyroglobulin antibodies (TgAb), and neck ultrasonography (US) 1 and 3 years after primary treatment were analyzed. Recurrence risk and disease status at 1 year were defined according to the American Thyroid Association (ATA) guidelines and as the presence or absence of SD after 3 years. Patients were grouped according to TSH level at 1 year: group 1, TSH <0.1 μUI/mL; group 2, TSH 0.1 to 0.5 μUI/mL; group 3, 0.5 to 2 μUI/mL; and group 4 >2 μUI/mL.

RESULTS

This study included 263 patients (70.9% female, median age 47.2 years) of whom the risk of recurrence was low in 170 (65%), intermediate-low in 63 (24%), and intermediate-high in 30 (11%). The response to initial treatment at 1 year was excellent in 149 (57%), biochemical incomplete in 18 (7%), indeterminate in 84 (32%), and structural incomplete in 12 (4%). Group 1 consisted of 53 (20%) patients, group 2 of 85 (32%), group 3 of 61 (23%), and group 4 of 64 (24%). The rate of SD at 1 and 3 years from primary treatment was not significantly different between TSH groups.

CONCLUSION

TSH suppression before the first response to treatment assessment does not appear to influence the rate of SD evaluated 1 and 3 years after primary treatment.

ABBREVIATIONS

ATA = American Thyroid Association; DTC = differentiated thyroid cancer; FTC = follicular thyroid cancer; LT4 = levothyroxine; PTC = papillary thyroid cancer; SD = structural disease; Tg = thyroglobulin; TgAb = antithyroglobulin antibodies; TSH = thyroid-stimulating hormone; US = ultrasonography.

Indirect Basal Metabolism Estimation in Tailoring Recombinant Human TSH Administration in Patients Affected by Differentiated Thyroid Cancer: A Hypothesis-Generating Study

PURPOSE

Recombinant human TSH (rhTSH) is currently used in follow-up of patients affected by differentiated thyroid cancer (DTC). Age, sex, weight, body mass index, body surface area (BSA) and renal function are known factors affecting serum TSH peak levels, but the proper rhTSH dose to deliver to single patient remains elusive. In this study, the correlations of basal metabolic rates with serum TSH peak following rhTSH administration were investigated.

METHODS

We evaluated 221 patients affected by thyroid cancer that received a standard dose rhTSH. Blood samples were collected at pre-established time points. Data on body weight, height, and BSA were collected. The Mifflin-St Jeor and Fleisch equations were used to assess basal metabolism.

RESULTS

The median value (range) of serum TSH peaks was 142 ± 53 μU/ml. Serum TSH peaks were significantly lower in males than in females (p = 0.04). TSH values also increased with age. Data showed a significant decrease of TSH peak levels at day 3 from the administration of rhTSH when basal metabolic rates increased (p = 0.002 and p = 0.009, respectively). Similar findings were observed at day 5 (p = 0.004 and p = 0.04, respectively). A multivariate analysis of several factors revealed that patients' basal metabolism (obtained using the Mifflin-St Jeor but not Fleisch equation) predicts serum TSH level peak at day 3 (p < 0.001). These results were used to generate a new formula based on Mifflin-StJeor equation which reveals as a promising tool in tailoring rhTSH dose.

CONCLUSION

Basal metabolism appears an improving factor in tailoring diagnostic rhTSH dose in patients affected by DTC.

Is Very High Thyroid Stimulating Hormone Level Required in Differentiated Thyroid Cancer for Ablation Success?

Objective:

Remnant ablation with radioactive iodine (I-131) is a successful form of treatment that aims to destroy the remaining residual tissue and/or metastatic tissue after total thyroidectomy in differentiated thyroid cancer (DTC) patients. High level of thyroid stimulating hormone (TSH) (≥30 mIU/L) is recommended for success of ablation treatment. In this retrospective study, our aim was to investigate whether the TSH levels at the time of ablation effect the success of radioactive iodine remnant ablation.

Methods:

Patients who were diagnosed with DTC, treated with bilateral total/near total thyroidectomy and who were referred for I-131 remnant ablation were included in this study. Patients with undetectable TSH-stimulated serum thyroglobulin (Tg) level, normal physical examination, negative results on whole body scan with I-131, and no evidence of neck lymph node metastasis on ultrasound were defined as disease-free. The correlation between TSH level at the time of ablation and ablation success was assessed.

Results:

Two hundred sixty one consecutive patients were included in the present study. Mean TSH level was 19.47±6 mIU/L in the 34 patients with TSH <30 mIU/L, while mean TSH level was 73.65±27 mIU/L in the 227 patients with TSH ≥30 mIU/L during I-131 remnant ablation. Ablation was unsuccessful in only one patient with TSH <30 mIU/L who had lung metastasis. Ablation was unsuccessful in 5.1% of patients with TSH ≥30 mIU/L. The effect of TSH level was not significant on ablation success (p=0.472).

Conclusion:

In conclusion, we think that a high TSH serum level alone is not a factor for the success of ablation. Age, presence of metastasis, extent of residual thyroid mass should also be considered. Especially, in the presence of metastatic tissue, obtaining adequate increase in TSH level is not always possible. The success of ablation at lower levels of TSH elevations may be sufficient for patients, and long-term hypothyroidism may not be required.

Analysis of Clinical Factors for the Determination of Optimal Serum Level of Thyrotropin After Recombinant Human Thyroid-Stimulating Hormone Administration

PURPOSE

To determine the optimal levels of thyroid-stimulating hormone (TSH) levels after administration of recombinant human TSH (rhTSH) to patients with differentiated thyroid cancer (DTC), we have analyzed the clinical parameters that affected the degree of the increase in serum levels of TSH.

METHODS

We retrospectively analyzed 276 patients with differentiated thyroid cancer (DTC), post-thyroidectomy and remnant ablation. Pearson's correlation coefficient test was used to evaluate the correlation between serum levels of TSH after rhTSH stimulation and various clinical factors, including age, sex, height, weight, body mass index (BMI), body surface area (BSA), serum blood urea nitrogen, creatinine, and estimated glomerular filtration rate (GFR). Linear regression analysis was used to determine the predictors of the degree of increase in serum TSH level after rhTSH stimulation.

RESULTS

After the rhTSH injections, all subjects achieved TSH levels of >30 μU/mL, with a mean of 203.8 ± 83.4 μU/mL. On univariate analysis, age (r = 0.255) and serum creatinine (r = 0.169) level were positive predictors for higher levels of serum TSH after rhTSH stimulation, while weight (r = -0.239), BMI (r = -0.223), BSA (r = -0.217), and estimated GFR (r = -0.199) were negative predictors. Multiple linear regression analysis revealed that serum creatinine was the most powerful independent predictor for serum levels of TSH, followed by age, BSA, and BMI.

CONCLUSIONS

An increment in serum TSH after rhTSH stimulation was significantly affected by age, BSA, BMI, and creatinine, with creatinine being the most powerful predictor. By understanding the difference in the increased levels of TSH in various subjects, their dose of rhTSH can be adjusted during scheduling for radioiodine ablation, or during follow-up (recurrence surveillance) after surgery and ablation.

Age and body composition influence TSH concentrations after administration of rhTSH

AIM

Previous studies listed body surface area (BSA), lean body mass (LBM), and age as modifying factors on the TSH concentrations after administration of recombinant human thyrotropin (rhTSH). The purpose of this study was to identify the main modifying factors on serum TSH levels and to compare the stimulation via single rhTSH injection after a short thyroid hormone withdrawal (THW) with that of the standard stimulating protocol.

PATIENTS, METHODS

106 patients with differentiated thyroid cancer (DTC) undergoing radioiodine therapy (RIT) after rhTSH administration were obtained through chart review. Two groups were evaluated: Group I was treated with a single rhTSH administration after two weeks of T3 therapy followed by one week of THW. Group II was stimulated according to the international standard protocol via rhTSH injections for two consecutive days. Serum TSH concentrations were documented prior to rhTSH administration (day 1 TSH), one day after (day 3 TSH) and 3-6 days after (mean 4.2 days, day 6 TSH) the last rhTSH injection. The following data was collected: age, gender, weight, height, BMI, LBM, BSA, residual thyroid tissue, CRP, creatinine, GFR, liver enzymes, alkaline phosphatase, cholesterol, and triglycerides.

RESULTS

Group I: Age combined with anthropometric factors like BMI (TSH increase and day 6 TSH), BSA (TSH decrease), and gender (day 6 TSH) are the main modifying factors on serum TSH concentrations after rhTSH administration. Group II: Age and lean body mass (LBM) showed a significant impact on day 3 TSH, TSH increase (day 3-day 1), and TSH decrease (day 6-day 3). Day 6 TSH was found to be influenced by GFR (group II).

CONCLUSION

Age and anthropometric parameters have significant independent influence on TSH concentrations after rhTSH injection in both groups. Anthropometric parameters (BSA, LBM) and demographic parameters (female gender) show strong influence on TSH concentrations. Further research should be conducted to examine the influence of body compartments on TSH levels through measuring total body water.

rhTSH-aided low-activity versus high-activity regimens of radioiodine in residual ablation for differentiated thyroid cancer: a meta-analysis

The effects of low-activity versus high-activity radioiodine regimens in thyroid remnant ablation for patients with differentiated thyroid carcinoma (DTC) under recombinant human thyrotropin (rhTSH) stimulation have been widely quoted but there has been no systematic review of the evidence. We undertook a systematic review of randomized controlled trials to assess the effects of low-activity radioiodine in thyroid remnant ablation in patients with DTC under rhTSH stimulation compared with high-activity radioiodine. Studies were obtained from computerized searches of MEDLINE, EMBASE, and the Cochrane Library (all until September 2012). Randomized controlled trials were included. Altogether, 637 patients with DTC who participated in three trials for residual ablation were included. Overall, studies had a low risk of bias. We found no statistically significant differences between low-activity (1.11/1.85 GBq) and high-activity (3.7 GBq) radioiodine treatment aided by rhTSH in terms of successful ablation rates on the basis of diagnostic scans [odds ratio (OR) 0.85, 95% confidence interval (CI) 0.49–1.47, P=0.56], thyroglobulin levels (OR 0.66, 95% CI 0.38–1.15, P=0.14), and health-related quality of life (mean difference 0.07, 95% CI −0.96 to 1.09, P=0.9). In addition, the subgroup analysis of 1.11 versus 3.7 GBq (OR 0.83, 95% CI 0.46–1.49, P=0.53) and 1.85 versus 3.7 GBq (OR 1, 95% CI 0.23–4.35, P=1) also showed no significant differences. The lower activity of 1.11 GBq showed significant benefit in terms of reduction in adverse events including neck pain, radiation gastritis, and salivary dysfunction during and after ablation (OR 0.63, 95% CI 0.42–0.93, P=0.02). Limited data from three randomized controlled trials suggested that an rhTSH-aided low radioiodine activity level of as low as 1.115 GBq may be sufficient for thyroid remnant ablation when compared with 3.7 GBq, with fewer common adverse effects in patients with metastasis-free DTC. Further evidence is needed to confirm the effects of low-activity radioiodine for thyroid remnant ablation. Radioiodine treatment of 1.11 GBq showed significant benefit in terms of reduction in adverse events including neck pain, radiation gastritis, and salivary dysfunction during and after ablation (OR 0.63, 95% CI 0.42–0.93, P=0.02). rhTSH-aided low radioiodine activity levels of 1.11 and 1.85 GBq are sufficient for thyroid remnant ablation as compared with 3.7 GBq, with fewer common adverse effects in patients with metastasis-free DTC. A well-designed study that compares low-activity with high-activity radioiodine ablation is needed to fully understand the long-term adverse effects and relapse or metastases.

Potential use of recombinant human thyrotropin in the treatment of distant metastases in patients with differentiated thyroid cancer

OBJECTIVE

In order to effectively treat differentiated thyroid cancer (DTC) with radioiodine (RAI) it is necessary to raise serum TSH levels either endogenously by thyroid hormone withdrawal (THW) or exogenously by administration of recombinant human TSH (rhTSH). The goal of this review is to present current data on the relative efficacy and side effects profile of rhTSH-aided versus THW-aided RAI therapy for the treatment of patients with distant metastases of DTC.

METHODS

We have searched the PubMed database for articles including the keywords "rhTSH", "thyroid cancer", and "distant metastases" published between January 1, 1996 and January 7, 2012. As references, we used clinical case series, case reports, review articles, and practical guidelines.

RESULTS

Exogenous stimulation of TSH is associated with better quality of life because it obviates signs and symptoms of hypothyroidism resulting from endogenous TSH stimulation. The rate of neurological complications after rhTSH and THW-aided RAI therapy for brain and spine metastases is similar. The rate of leukopenia, thrombocytopenia, xerostomia, and pulmonary fibrosis is similar after preparation for RAI treatment with rhTSH and THW. There is currently a controversy regarding RAI uptake in metastatic lesions after preparation with rhTSH versus THW, with some studies suggesting equal and some superior uptake after preparation with THW. Analysis of available retrospective studies comparing survival rates, progression free survival, and biochemical and structural response to a dosimetrically-determined dose of RAI shows similar efficacy after preparation for therapy with rhTSH and THW.

CONCLUSION

The rhTSH stimulation is not presently approved by the FDA as a method of preparation for adjunctive therapy with RAI in patients with metastatic DTC. Data on rhTSH compassionate use suggest that rhTSH stimulation is as equally effective as THW as a method of preparation for dosimetry-based RAI treatment in patients with RAI-avid metastatic DTC.

Impact of renal function and demographic/anthropomorphic variables on peak thyrotropin after recombinant human thyrotropin stimulation: a stepwise forward multiple-regression analysis

BACKGROUND

When applying the recommended standard doses of recombinant human thyrotropin (rhTSH) in the diagnostic/therapeutic management of patients with differentiated thyroid cancer (DTC), the resulting peak TSH levels vary extensively. Previous studies applying multivariate statistics identified patient-inherent variables influencing the rhTSH/peak TSH relation. However, those results were inconclusive and partly conflicting. Notably, no independent role of renal function was substantiated, despite the fact that the kidneys are known to play a prominent role in TSH clearance from blood. Therefore, the study's aim was to investigate the impact of renal function on the peak TSH concentration after the standard administration of rhTSH used in the management of thyroid cancer. The second objective was to calculate a ranking regarding the effect sizes of the selected variables on the peak TSH.

METHODS

There were 286 patients with DTC included in the study. Univariate and multivariate analyses were performed, testing the correlation of serum creatinine and glomerular filtration rate (GFR) as surrogate parameters of renal function, age, sex, weight, height, and body surface area (BSA) with the peak TSH level. In six additional patients, the subsequent TSH pharmacokinetics after the TSH peak were measured and qualitatively compared.

RESULTS

By univariate analyses, TSH correlated negatively with BSA, GFR, weight, and height, and positively with age, female sex, and serum creatinine (p<0.001). On the multivariate analysis, the stepwise forward multiple linear regression revealed BSA and renal function as the two most influential independent variables, followed by age, sex, and height. The pharmacokinetic datasets indicated that these identified parameters also influence the TSH decline over time.

CONCLUSION

Identifying those patients with a favorable combination of parameters predicting a high-peak TSH is the first step toward an individualization of rhTSH dosing. Additionally, the subsequent TSH decrease over time needs to be taken into account. A complete understanding of the interrelation of the identified key parameters and both the TSH peak and subsequent TSH pharmacokinetics might allow for a more personalized rhTSH dosage strategy to achieve sufficient TSH levels instead of the fixed dosing procedure used at present.

Sorafenib therapy decreases the clearance of thyrotropin

OBJECTIVE

Thyroid function abnormalities are common during treatment with tyrosine kinase inhibitors such as sorafenib. Suggested causes are direct effects on thyroid tissue and increased extrathyroidal metabolism of serum thyroxine and 3,5,3-triiodothyronine. We postulated that tyrosine kinase inhibitors may affect the peripheral metabolism of TSH as well. The effect of sorafenib on TSH clearance was studied.

DESIGN

In a study of athyreotic patients on TSH suppression therapy, TSH concentrations were measured after recombinant human TSH (rhTSH) injections before and after 26 weeks of sorafenib therapy.

METHODS

Before and after the last week of sorafenib therapy, 20 patients with progressive differentiated thyroid carcinoma received a standard dose regimen of two injections 0.9 mg rhTSH on two consecutive days. TSH concentrations were measured 48 h (TSH(48 h)) and 96 h (TSH(96 h)) after the first rhTSH injection. The area under the curve (TSH-AUC), reflecting TSH content between 48 and 96 h following rhTSH administration, was calculated.

RESULTS

TSH(48 h) levels (120.5 mU/l before vs 146.3 mU/l after; P=0.029), TSH(96 h) levels (22.0 mU/l before vs 35.5 mU/l after; P=0.001), and TSH-AUC (142.7 vs 186.8 mU/l; P=0.001) were significantly higher after sorafenib treatment. Higher sorafenib doses were associated with increased changes in TSH(96 h) and TSH-AUC. In two patients, TSH levels after sorafenib therapy exceeded 200 mU/l.

CONCLUSIONS

Sorafenib therapy is accompanied by higher rhTSH levels, probably due to a decreased TSH clearance. Further studies are recommended to clarify whether a decreased clearance of TSH is sorafenib specific.

Age modifies the response to recombinant human thyrotropin

BACKGROUND

A standardized protocol is used to administer recombinant human thyrotropin (rhTSH) in preparation for diagnostic studies and treatment in patients with thyroid cancer. The expectation is that serum TSH concentrations will peak on the day after the second injection and will be sufficiently elevated to stimulate uptake of radioiodine. We wished to test the hypothesis that TSH concentrations achieved after rhTSH injection are influenced by age.

METHODS

Patients with thyroid cancer undergoing diagnostic radioiodine scanning were identified by chart review. Serum TSH concentrations were documented 24 and 72 hours after two rhTSH injections (days 3 and 5, respectively). Responses were subdivided into four ascending patient age groups: <35, 35-49, 50-64, and >64 years. TSH concentrations after rhTSH administration were documented according to patient age.

RESULTS

There was a significant correlation between the serum TSH concentrations at both days 3 and 5 and patient age (p < 0.0001). None of the other factors examined (gender, menopausal status, weight, body mass index, baseline TSH, serum creatinine, and estimated glomerular filtration rate) were significant in multivariate analyses. The mean TSH concentration on day 3 increased significantly when patients were divided into the aforementioned groups of ascending age (96, 107, 142, and 196 mIU/L, p < 0.0001). Day 5 concentrations increased in a similar manner.

CONCLUSIONS

Both days 3 and 5 TSH concentrations were higher in older individuals after rhTSH administration. This finding did not appear to be related to body weight, body mass index, or glomerular filtration rate in a simple manner. The TSH concentration achieved may be a result of complex interactions between distribution within fat and muscle body compartments, hepatic function, and renal function. Prospective studies could examine whether the magnitude of the TSH elevation after rhTSH administration affects diagnostic or therapeutic efficacy.

Recombinant human thyrotropin (rhTSH) aided radioiodine treatment for residual or metastatic differentiated thyroid cancer

BACKGROUND

For patients with differentiated thyroid cancer (DTC) following thyroidectomy, thyroid hormone withdrawal (THW) for four to six weeks has been used for decades to increase serum thyroid-stimulating hormone (TSH) concentrations in order to enhance iodine-131 uptake by normal thyroid cells and differentiated thyroid tumour cells. Exogenous stimulation with recombinant human thyroid-stimulating hormone (rhTSH) offers an alternative to THW while avoiding the morbidity of hypothyroidism. However, the efficacy of rhTSH-aided iodine-131 treatment for residual or metastatic DTC has not been prospectively assessed.

OBJECTIVES

To assess the effects of rhTSH-aided radioiodine treatment for normal residual or metastatic DTC.

SEARCH STRATEGY

We obtained studies from computerised searches of MEDLINE, EMBASE and The Cochrane Library (all until November 2009), and paper collections of conferences held in Chinese.

SELECTION CRITERIA

Randomised controlled clinical trials and quasi-randomised controlled clinical trials comparing the effects of rhTSH with THW on iodine-131 treatment for residual or metastatic differentiated thyroid cancer with at least six months of follow up.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed risk of bias and extracted data.

MAIN RESULTS

Altogether 223 patients with DTC participated in four trials. Overall, studies had a high risk of bias. We found no statistically significant differences between rhTSH and THW treatment in terms of successful ablation rate but significant benefits in radiation exposure to blood and bone marrow. One trial reported on benefits in some domains of health-related quality of life. There were no deaths and no serious adverse effects in DTC patients treated with either rhTSH or THW. Maximum follow up was 12 months. None of the included trials investigated complete or partial remission of metastatic tumour, secondary malignancies or economic outcomes. We did not find sufficient data comparing rhTSH with THW-aided radioiodine treatment for metastatic DTC.

AUTHORS' CONCLUSIONS

Results from four randomised controlled clinical trials suggest that rhTSH is as effective as THW on iodine-131 thyroid remnant ablation, with limited data on significant benefits in decreased whole body radiation exposure and health-related quality of life. It is still uncertain whether lower iodine-131 doses (1110 MBq or 1850 MBq versus 3700 MBq) are equally effective for remnant ablation under rhTSH stimulation. Randomised controlled clinical trials are needed to guide treatment selection for metastatic differentiated thyroid cancer.

Recombinant human thyroid stimulating hormone in 2008: focus on thyroid cancer management

Radioiodine (RAI) ablation following thyroidectomy is standard of care treatment for patients with intermediate or high risk differentiated thyroid cancer. Traditionally, this has been achieved by forgoing thyroid hormone replacement postoperatively, allowing endogenous thyroid stimulating hormone (TSH) levels to rise. This rise in TSH provides the stimulus for RAI uptake by the thyroid remnant, but is associated with clinical hypothyroidism and its associated morbidities. Recombinant human TSH (rhTSH, thyrotropin alfa [Thyrogen^®], Genzyme Corporation, Cambridge, MA, USA) was developed to provide TSH stimulation without withdrawal of thyroid hormone and clinical hypothyroidism. Phase III studies reported equivalent detection of recurrent or residual disease when rhTSH was used compared with thyroid hormone withdrawal (THW). These trials led to its approval as an adjunctive diagnostic tool for serum thyroglobulin (Tg) testing with or without RAI imaging in the surveillance of patients with differentiated thyroid cancer. Recently, rhTSH was given an indication for adjunctive preparation for thyroid remnant ablation after phase III studies demonstrated comparable outcomes for rhTSH preparation when compared with THW. Importantly, rhTSH stimulation has been found to be safe, well tolerated, and to result in improved quality of life. Here, we review the efficacy and tolerability studies leading to the approval for the use of rhTSH in well-differentiated thyroid cancer management.

Review on the occasion of a decade of recombinant human TSH: prospects and novel uses

The introduction of recombinant human thyroid-stimulating hormone (rhTSH) almost a decade ago represents a remarkable achievement in the history of clinical thyroidology. rhTSH now contributes substantially to the diagnostic approach to thyroid cancer, offering a reliable and safe alternative to thyroid hormone withdrawal by avoiding the morbidity of hypothyroidism. Several recent studies have also demonstrated the efficacy of radioiodine ablation of thyroid remnants after preparation with rhTSH. Moreover, the use of rhTSH in this context is associated with a lower whole body exposure to radiation compared to thyroid hormone withdrawal. Although not approved officially, rhTSH-assisted treatment of locoregional or distant metastatic disease may be the treatment of choice for patients in whom hypothyroidism may be relatively contraindicated, such as the very young and the aged, although additional efficacy studies are necessary. The compound has also been shown to be useful in the treatment of nontoxic multinodular goiter, especially when the radioiodine uptake is low. Finally, rhTSH may prove to be useful in studying the functional reserve of thyroid in the aging process, as well as the putative role of the TSH receptor in extrathyroidal tissue, such as lymphocytes, osteocytes, and adipocytes.