Effect of various doses of recombinant human thyrotropin on the thyroid radioactive iodine uptake and serum levels of thyroid hormones and thyroglobulin in normal subjects

Comparison of 1.1 GBq and 2.2 GBq Activities in Patients with Low-Risk Differentiated Thyroid Cancer Requiring Postoperative 131I Administration: A Real Life Study

OBJECTIVES

To compare the efficacy of low and moderate ¹³¹I activities in low-risk differentiated thyroid carcinoma (DTC) patients requiring postoperative thyroid remnant ablation in a real-world clinical setting.

METHODS

We retrospectively reviewed the records of 299 low-risk DTC patients (pT1-T2, Nx(0) Mx) who had undergone (near)-total thyroidectomy followed by ¹³¹I therapy, using either low (1.1 GBq) or moderate (2.2 GBq) radioiodine activities. The response to initial treatments was evaluated after 8-12 months, and patient responses were classified according to the 2015 American Thyroid Association guidelines.

RESULTS

An excellent response was observed in 274/299 (91.6%) patients, specifically, in 119/139 (85.6%) and 155/160 (96.9%) patients treated with low and moderate ¹³¹I activities, respectively (p = 0.029). A biochemically indeterminate or incomplete response was observed in seventeen (22.2%) patients treated with low ¹³¹I activities and three (1.8%) patients treated with moderate ¹³¹I activities (p = 0.001). Finally, five patients showed an incomplete structural response, among which three and two received low and moderate ¹³¹I activities, respectively (p = 0.654).

CONCLUSIONS

When ¹³¹I ablation is indicated, we encourage the use of moderate instead of low activities, in order to reach an excellent response in a significantly larger proportion of patients, including patients with the unexpected persistence of the disease.

Benign thyroid nodules respond to a single administration of 0.3mg recombinant human thyrotropin with highly variable volume increase

INTRODUCTION

The nature of thyroid nodules is heterogenous. Most of them are benign and, in the absence of pressure symptoms of adjunct structures, no treatment is needed. Our objective was to investigate the acute effects of a low dose of recombinant human TSH (rhTSH) on the volume of benign thyroid nodules.

METHODS

we studied 27 nodules (14 isoechoic and 13 hypoechoic) in 15 (11 women and 4 men; mean age: 51.0 ± 15.9 years) consecutive patients with one to three well-separated asymptomatic benign thyroid nodules. All subjects were euthyroid, with negative thyroid antibodies, and none received levothyroxine. The total thyroid volume and thyroid nodule volume were sonographically determined by two independent examiners (P.B. and M.M.) before, 48 hours and 6 months post intramuscular (IM) administration of 0.3mg rhTSH, and the mean values of the two examiners' measurements were used; thyroid function tests were obtained at the same time points.

RESULTS

The mean volume of isoechoic nodules increased by 57.3%, of hypoechoic nodules by 46.6% and of the surrounding thyroid parenchyma by 70.4% 48 hours post-rhTSH; mean volumes had returned to baseline levels 6 months later. A large variance in the volume change responses was observed. The relative change in nodule volume (defined as the percent change in nodule volume divided by the percent change in the surrounding parenchyma) from baseline to 48 hours was significantly higher in isoechoic versus hypoechoic nodules (p<0.05).

CONCLUSIONS

A single dose of 0.3 mg rhTSH transiently increased the volume of benign thyroid nodules. The increase was more pronounced in isoechoic nodules and had a great variability. Our findings could be useful in the management of benign thyroid nodules, by helping in understanding which nodules would be more responsive to TSH suppression therapy.

Determining the frequency of thyroid parameter measurements following rhTSH administration in a healthy, older population

Serial thyroid hormone measurement in blood following recombinant human thyroid stimulating hormone (rhTSH) administration has not been studied extensively in healthy, older populations. Current methods involve measurement of thyroid hormones mostly at 4 to 24 hours following rhTSH administration. We tailored existing protocols to measure thyroid hormones at high frequencies following 0.1mg rhTSH intramuscular (i.m.) administration to identify optimal measurement points in our healthy, older population. We designed a method with frequent blood sampling in the first 8 hours, followed by blood sampling at 24, 48 and 72 hours after rhTSH administration to measure TSH, thyroxine (T4), free T4 (fT4), triiodothyronine (T3), free T3 (fT3) and thyroglobulin (Tg). In total, we performed a series of 17 blood withdrawals in four consecutive days. Following 0.1mg rhTSH (i.m.) administration, mean thyroid parameters showed great inter-individual variation and variation over time. Mean TSH concentration showed the greatest variation in the first 8 hours following rhTSH administration. Mean T4, fT4, T3 and fT3 started showing variation from 2 hours after rhTSH administration, and were less variable than mean TSH concentration. Mean Tg was only variable at later time points, namely 24, 48 and 72 hours after rhTSH administration. In this novel method with high frequency blood sampling following 0.1mg rhTSH (i.m.) administration, we identify optimal time points for measuring thyroid gland output in a healthy, older population. Our methods and findings may be informative for further thyroid but also other hormonal axis studies.•

Thyroid metabolism

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Blood sampling frequency

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Geriatrics and longevity

Lipidomic Perturbations in Cynomolgus Monkeys are Regulated by Thyroid Stimulating Hormone

Thyroid disease affects an estimated 200 million people worldwide, and is commonly associated with increased blood lipid levels. However, the mechanism by which thyroid-stimulating hormone (TSH) affects lipid profiles is not clear. Twenty-four cynomolgus monkeys were treated with a novel exogenous recombinant human TSH (rhTSH) (SNA001) at 9 μg kg⁻¹, 22 μg kg⁻¹, or 54 μg kg⁻¹, and reference rhTSH (Thyrogen^®) at 22 μg kg⁻¹. The primary TSH (SNA001) pharmacokinetic (PK) parameters increased in a dose-dependent manner across the dose range of 9 μg kg⁻¹, 22 μg kg⁻¹, or 54 μg kg⁻¹. Peak triiodothyronine (T3) and thyroxine (T4) levels were reached within 24 h after rhTSH administration, which was delayed by approximately 20 h. In total, 420 lipid species were detected and quantified by ultra-performance liquid chromatography high resolution spectrometry (UPLC-HR-MS)-based lipidomics. Notably, peak levels of lipid accumulation, particularly sphingomyelin (SM) and triglycerides (TG), appeared at 4 and 24 h, which was consistent with the pattern of TSH and T3/T4 levels, respectively. According to weighted correlation network analysis (WGCNA), perturbations of many lipid species were strongly correlated with TSH and T3/T4 levels. TSH and the stimulated T3/T4 levels and lipid profiles following SNA001 administration were comparable to those after administration of the reference rhTSH (Thyrogen^®). The plasma lipidome and changes in lipid levels after rhTSH stimulation were associated with TSH and T3/T4 concentrations. T3/T4 and lipid profiles were delayed after TSH stimulation. Such phenomena require further exploration.

A pre-ablative thyroid-stimulating hormone with 30-70 mIU/L achieves better response to initial radioiodine remnant ablation in differentiated thyroid carcinoma patients

Our aim was to clarify the optimum pre-ablative thyroid-stimulating hormone (TSH) level for initial radioiodine remnant ablation (RRA) in patients with differentiated thyroid carcinoma (DTC). From December 2015 to May 2019, 689 patients undergone RRA at Nuclear Medicine Department, Second Hospital of Shandong University were included in the study. Patients were categorized by their pre-ablative TSH level grouping of < 30, 30–70 and ≥ 70 mIU/L. Response to RRA were evaluated as complete response (including excellent and indeterminate response) and incomplete response (including biochemical and structural incomplete response) after a follow-up of 6–8 months. Multivariable binary logistic regression model was used to explore the optimum pre-ablative TSH level range and independent factors associated with response to RRA. Rates of complete response to RRA were 63.04%, 74.59% and 66.41% in TSH level groups of < 30, 30–70 and ≥ 70 mIU/L, separately. With multivariate analysis, the study found that pre-ablative TSH levels, gender and lymph node dissection were independent predictors of response to RRA. TSH between 30 and 70 mIU/L had a higher rate of complete response compared with TSH < 30 mIU/L, OR 0.451 (95% CI 0.215–0.958, P = 0.036). A pre-ablative TSH level of 30–70 mIU/L was appropriate for patients with DTC to achieve a better response to RRA.

Early preablation rhTSH-stimulated thyroglobulin predicts outcome of differentiated thyroid cancer (DTC) patients

AIM

Total thyroidectomy and risk-adapted 131-radioiodine therapy (RaIT) are the treatments of choice in differentiated thyroid cancer (DTC) patients. The response to treatments is assessed 6-12 months after RaIT. However, thyroglobulin (Tg) values obtained just before RaIT also provide reliable informations on patients'outcome. As available data were mostly obtained in hypothyroid status, we evaluated the predictive role of preablation-Tg in patients underwent RaIT after rhTSH stimulation.

MATERIAL AND METHODS

We enrolled 299 low-to-intermediate risk DTC patients underwent rhTSH-stimulated RaIT (standard protocol). Serum Tg levels were measured before rhTSH administration (basal Tg), before RaIT (early-stimulated Tg), and 2 days after RaIT (late-stimulated Tg). The early response assessment was done 12 months after RaIT according to 2015 American Thyroid Association (2015 ATA) criteria.

RESULTS

Most patients (277/299, 92.6%) had an excellent response (ER) to RaIT, while 15/299 (5.1%) and 7/299 (2.3%) patients showed biochemical incomplete/indeterminate response or persistent structural disease, respectively. At receiver operating characteristic analysis, the optimal cutoff to predict ER was set at 1.55 (AUC = 0.792), 2.6 (AUC = 0.931), and 4.9 (AUC = 0.874) ng/mL, for basal, early-, and late-stimulated Tg, respectively. The overall sensitivity, specificity, accuracy, positive predictive value (PPV), and negative predictive value (NPV) for basal, early-, and late-stimulated Tg were 50%, 96.7%, 93.3%, 55%, and 96.1%; 90.9%, 84.5%, 84.9%, 31.7%, and 99.1%; and 90.9%, 71.8%, 73.2%, 20.4%, and 99%, respectively. In univariate and multivariate logistic regression analysis, early-stimulated Tg cutoff resulted as an independent prognostic marker for predicting ER regardless of gender, age, histotype, histological variant, tumor size, risk classification, and stage of disease.

CONCLUSION

Early-stimulated Tg is a reliable diagnostic tool for predicting the response to primary treatment of DTC.

Familial Longevity is Associated with an Attenuated Thyroidal Response to Recombinant Human Thyroid Stimulating Hormone

CONTEXT

Longevity is associated with higher circulating levels of TSH in the absence of differences in circulating thyroid hormones (TH), as previously observed in F2 members of long-lived families (F2-LLS) and their partners (F2-Con). The mechanism underlying this observed difference remains unknown.

OBJECTIVE

We hypothesized that the thyroid gland of members from long-lived families are less responsive to TSH stimulation, thereby requiring higher circulating TSH levels to maintain adequate TH levels.

METHODS

We performed a case-control intervention study with a single intramuscular (gluteal) injection with 0.1 mg recombinant human TSH in a subgroup of 14 F2-LLS and 15 similarly aged F2-Con. They were followed for 4 days. No serious adverse events were reported. For analyses, we compared time trajectories of TSH and TH, and the ratio of TH to TSH using area under the curve (AUC) calculations.

RESULTS

The AUC free T4/AUC TSH ratio was significantly lower in F2-LLS than in F2-Con (estimated mean [95% confidence interval] 1.6 [1.2-1.9] and 2.2 [1.9-2.6], respectively, P = 0.01). The AUC thyroglobulin/AUC TSH ratio was also lower in F2-LLS than in F2-Con (median [interquartile range] 2.1 [1.4-3.6] and 3.2 [2.7-7.4], respectively, P = 0.04). We observed the same trend with the AUC free T3/AUC TSH ratio, although the difference was not statistically significant (estimated mean [95% confidence interval] 0.6 [0.4-0.7] and 0.7 [0.6-0.8], respectively, P = 0.07).

CONCLUSIONS

The present findings show that members of long-living families have a lower thyroid responsivity to TSH compared with their partners.

THYROGLOBULIN AS A TUMOR MARKER IN DIFFERENTIATED THYROID CANCER - CLINICAL CONSIDERATIONS

SUMMARY – Initial treatment of the majority of patients with differentiated thyroid cancer (DTC) includes total thyroidectomy. Postoperative ablation therapy with radioactive iodine (I-131) is indicated in all high-risk patients, however, there is disagreement regarding its use in low- and intermediate-risk patients. Over the last few decades, thyroglobulin (Tg) has been established as the primary biochemical tumor marker for patients with DTC. Thyroglobulin can be measured during thyroid hormone therapy or after thyroid-stimulating hormone (TSH) stimulation, through thyroid hormone withdrawal or the use of human recombinant TSH. In many studies, the cut-off value for adequate Tg stimulation is a TSH value ≥30 mIU/L. However, there is an emerging body of evidence suggesting that this long-established standard should be re-evaluated, bringing this threshold into question. Recently, a risk stratification system of response to initial therapy (with four categories) has been introduced and Tg measurement is one of the main components. The relationship between the Tg/TSH ratio and the outcome of radioiodine ablation has also been studied, as well as clinical significance of serum thyroglobulin doubling-time. The postoperative serum Tg value is an important prognostic factor that is used to guide clinical management, and it is the most valuable tool in long term follow-up of patients with DTC.

Quantitative Measurement of the Thyroid Uptake Function of Mouse by Cerenkov Luminescence Imaging

Cerenkov luminescence imaging (CLI) has been an evolutional and alternative approach of nuclear imaging in basic research. This study aimed to measure the ¹³¹I thyroid uptake of mouse using CLI for assessment of thyroid function. Quantification of ¹³¹I thyroid uptake of mice in euthyroid, hypothyroid and hyperthyroid status was performed by CLI and γ-scintigraphy at 24 hours after injection of ¹³¹I. The ¹³¹I thyroid uptake was calculated using the equation: (thyroid counts − background counts)/(counts of injected dose of ¹³¹I) × 100%. Serum T4 concentration was determined to evaluate the thyroid function. The radioactivity of ¹³¹I was linearly correlated with the CL signals in both in vitro and in vivo measurements. CLI showed a significant decrease and increase of ¹³¹I thyroid uptake in the mice in hypo- and hyperfunctioning status, respectively, and highly correlated with that measured by γ-scintigraphy. However, the percent thyroid uptake measured by CLI were one-fifth of those measured by γ-scintigraphy due to insufficient tissue penetration of CL. These results indicate that CLI, in addition to nuclear imaging, is able to image and evaluate the ¹³¹I thyroid uptake function in mice in preclinical and research settings.

Early stimulated thyroglobulin for response prediction after recombinant human thyrotropin-aided radioiodine therapy

OBJECTIVE

Measurement of recombinant human thyrotropin (rhTSH)-stimulated thyroglobulin (Tg) is generally recommended 72 h after the second rhTSH injection. However, due to the acute effect of I-131 on thyrocytes, Tg measured after radioiodine therapy (RIT) would not accurately reflect the thyroid tissue burden. We aimed to determine predictive values of serum Tg level measured just before rhTSH-aided RIT and to compare the results obtained just after RIT in patients with differentiated thyroid carcinoma (DTC).

METHODS

We evaluated 150 patients with DTC who underwent rhTSH-aided RIT (2.96-6.66 GBq) after total thyroidectomy between 2009 and 2014. Serum Tg level was measured 24 h (early Tg) and 72 (or 96) h (delayed Tg) after the second rhTSH injection. An excellent response was defined based on the latest American Thyroid Association Guidelines. Univariate and multivariate analyses were performed for early Tg, delayed Tg, and other clinical variables.

RESULTS

In the multivariate analysis, tumor size [odds ratio (OR) 1.716; 95% confidence interval (CI) 1.019-2.882; p = 0.042] and early Tg level (OR 2.012; 95% CI 1.384-2.925, p < 0.001) independently predicted excellent responses. The cutoff for the best early Tg level to predict a non-excellent response was 2.0 ng/mL. Delayed Tg was not a significant predictor (OR 0.992; 95% CI 0.969-1.015; p = 0.492).

CONCLUSIONS

Early stimulated Tg significantly predicted therapeutic response after rhTSH-aided RIT in patients with DTC. Therefore, serum Tg should be measured before RIT to predict therapeutic responses.

Cellulose Fibers Constructed Convenient Recyclable 3D Graphene-Formicary-like δ-Bi2O3 Aerogels for the Selective Capture of Iodide

Radioiodine is highly radioactive and acutely toxic, which can be a serious health threat, and requires effective control. To fully utilize an adsorbent and reduce the overall production cost, successive recycling applications become necessary. Here, 3D formicary-like δ-Bi₂O₃ (FL-δ-Bi₂O₃) aerogel adsorbents were synthesized using a one-pot hydrothermal method. In this hybrid structure, abundant flowerlike δ-Bi₂O₃ (MR-δ-Bi₂O₃) microspheres were inlaid into the interconnected ant nest channel, forming a 3D hierarchical structure, which is applied as an efficient adsorbent with easy recovery for radioiodine removal. Notably, the FL-δ-Bi₂O₃ aerogel adsorbent exhibited a very high uptake capacity of 2.04 mmol/g by forming an insoluble Bi₄I₂O₅ phase. Moreover, the FL-δ-Bi₂O₃ worked in a wide pH range of 4-10 and displayed fast uptake kinetics and excellent selectivity due to the 3D porous interconnected network and larger specific surface area. Importantly, the recycling process is easy, using only tweezers to directly move the 3D aerogel adsorbents from one reaction system to another. Therefore, the FL-δ-Bi₂O₃ aerogel may be a promising practical adsorbent for the selective capture of radioactive iodide.

In Patients With Low- to Intermediate-Risk Thyroid Cancer, a Preablative Thyrotropin Level of 30 μIU/mL Is Not Adequate to Achieve Better Response to 131I Therapy

PURPOSE

The optimal preablative level of thyrotropin (TSH) for patients with differentiated thyroid cancer (DTC) to achieve better response after I ablation remains unknown. The objective of this study was to assess whether a higher preablative TSH level above 30 μIU/mL is associated with better response to I therapy in low- to intermediate-risk DTC and to explore the potential factors that may impact their responses.

PATIENTS AND METHODS

A total of 204 consecutive non-high-risk patients were retrospectively reviewed. Serum TSH and thyroglobulin (Tg) levels were measured right before I treatment after thyroxine hormone withdrawal (THW). Patients were categorized by their preablative TSH level grouping of 30 to less than 60 (n = 11), 60 to less than 90 (n = 61), 90 to less than 120 (n = 56), 120 to less than 150 (n = 33), and 150 μIU/mL or greater (n = 43). Responses to I therapy were evaluated as excellent, indeterminate, biochemical incomplete, or structural incomplete response (ER, IDR, BIR, or SIR) after a mean follow-up of 20.3 months. Initial risk factors (age, sex, T and N status by AJCC/UICC TNM staging system, and thyroid remnant), the administered dose of I and response to I therapy were compared among different preablative TSH groups. Multivariate analysis was further performed to identify factors associated with incomplete response (IR, including BIR and SIR).

RESULTS

Except the significant correlation between younger age and higher preablative TSH level (P = 0.001), the 5 TSH groups did not differ in other related prognostic factors or dose of I (all P > 0.05). Among each ascending TSH group, ER was observed in 54.5%, 68.9%, 73.2%, 69.7%, and 60.5%, respectively, whereas IR was observed in 18.2%, 18.0%, 7.1%, 9.1%, and 20.9%, respectively. Group 90 to less than 120 μIU/mL presented the highest rate of ER and lowest rate of IR. In the multivariate analysis, preablative TSH level, in addition to preablative Tg, was also an associated factor for response to I therapy (P = 0.048).

CONCLUSIONS

A preablative TSH level of 90 to less than 120 μIU/mL might be more appropriate for patients with low- to intermediate-risk DTC to achieve better response to I therapy.

Thyroglobulin levels measured at the time of remnant ablation to predict response to treatment in differentiated thyroid cancer after thyroid hormone withdrawal or recombinant human TSH

The objective of our study was to evaluate the prognostic value of stimulated thyroglobulin levels at the moment of remnant ablation for predicting an initial excellent or a structural incomplete response to treatment according to the risk of recurrence in patients with differentiated thyroid cancer. Patients were divided into two groups according to the preparation mode for remnant ablation (thyroid hormone withdrawal or recombinant human TSH). We included 219 patients followed-up for at least for 24 months after remnant ablation. The primary endpoint was the best response to initial therapy assessed in the first 9-18 months of follow-up. An excellent response was observed in 45.1 % of patients prepared after recombinant human TSH compared to 44.6 % of patients prepared after thyroid hormone withdrawal (P = NS). The cutoff value of thyroglobulin level after recombinant human TSH for predicting an excellent response was 8 ng/ml (n = 51), with a sensitivity of 73.9 %, and a positive predictive value of 61 %. It was similar for patients with low vs. intermediate to high risk of recurrence. This cutoff value for thyroglobulin level after thyroid hormone withdrawal was 22 ng/ml (n = 168), with a sensitivity of 94.7 % and a positive predictive value of 61.7 %. In the thyroid hormone withdrawal group the thyroglobulin cutoff level was 12 ng/ml for low-risk patients compared to 16 ng/ml for those with intermediate to high risk of recurrence (P = 0.003). The cutoff value of the thyroglobulin level for predicting a structural incomplete response to initial treatment was 20 ng/ml after rhTSH, with a negative predictive value of 91.4 %. This level was higher in thyroid hormone withdrawal group, and it was established at 25 ng/ml, with a negative predictive value of 97.7 %. The stimulated Tg level seems to be different depending on the preparation mode (rhTSH or THW) for RA. It has a high NPV to predict the absence of a structural incomplete response and it is also a good predictor of the initial excellent response and the NED status at the end of follow-up.

Prediction of radioactive iodine remnant ablation failure in patients with differentiated thyroid cancer: A cohort study of 740 patients

BACKGROUND

The purpose of this study was to detect parameters that could serve as predictors of radioactive iodine (I-131) ablation failure in patients with low-risk and intermediate-risk differentiated thyroid carcinoma (DTC).

METHODS

Our cohort study included 740 patients with DTC who received postoperative I-131 remnant ablation. Anthropometric, biochemical, and pathohistological parameters were analyzed and correlated with ablation outcome using multivariable logistic regression models.

RESULTS

Treatment failure rates were higher in patients <53 years, with N1a classification, and lymph node capsular invasion. In patients with N1a disease, thyroglobulin (Tg) > 2.4 ng/mL predicted treatment failure with 93.8% sensitivity and 52.5% specificity, and in patients with N1b disease, Tg > 14.9 ng/mL with 77.8% sensitivity and 92.9% specificity. I-131 activity was not associated with treatment outcome.

CONCLUSION

Patients < 53 years old, with higher Tg levels, N1a classification, and lymph node capsular invasion have a higher risk of ablation failure. Stimulated Tg is an excellent predictor of treatment failure in patients with N1 disease. © 2016 Wiley Periodicals, Inc. Head Neck 39: 109-115, 2017.

Serum thyrotropin level of 30 μIU/mL is inadequate for preablative thyroglobulin to serve as a prognostic marker for differentiated thyroid cancer

PURPOSE

Preablative-stimulated thyroglobulin (ps-Tg) has manifested its potential for predicting prognosis in patients with differentiated thyroid carcinoma (DTC), but its level can be affected by thyrotropin (TSH). The objective of this study was to evaluate the utility of ps-Tg in predicting individual response after radioactive iodine (RAI) therapy, and further explore the appropriate TSH level for ps-Tg to serve as a prognostic marker in DTC without initial distant metastasis (DM).

METHODS

A total of 208 consecutive non-DM DTC patients with serial ps-Tg, TSH, and anti-Tg antibody (TgAb) measured simultaneously were enrolled. The initial and last measurements of ps-Tg were marked as Tg1 and Tg2, respectively, with a median interval of 8 days, so does TSH. Clinical response was retrospectively evaluated as excellent, indeterminate, biochemical incomplete, or structural incomplete response (ER, IDR, BIR, or SIR) after a mean follow-up of 21.5 months. Tg1 and Tg2 were tested and compared for their performances in predicting ER and incomplete response (IR, including BIR and SIR) by receiver operating characteristic (ROC) curve analysis. The 416 ps-Tg levels (Tg1 and Tg2) were then categorized by their corresponding TSH grouping of 30-<60 (n = 100), 60-<90 (n = 131), 90-<120 (n = 99), and ≥120 μIU/mL (n = 86), and the predictive performances were further compared among TSH groups.

RESULTS

Tg2, with a higher corresponding TSH level than Tg1 (median: 104.763 vs. 65.046 μIU/mL), presented higher area under the ROC curve (AUC) in predicting both ER and IR (ER: 0.889 vs. 0.836, P = 0.003; IR: 0.925 vs. 0.869, P = 0.046). The performances of ps-Tg in predicting ER and IR were both improved significantly as TSH rose from 30-<60 to 60-<90 μIU/mL, with an increase in AUC from 0.810 to 0.888 in predicting ER (P = 0.006) and from 0811 to 0.937 in predicting IR (P = 0.014), respectively. However, this kind of benefit was not further enlarged as TSH rose from 60-<90 to 90-<120 μIU/mL (both P > 0.05).

CONCLUSION

In comparison with the TSH context of 30 μIU/mL, a higher preablative TSH level of 60-<90 μIU/mL might be more appropriate for ps-Tg to serve as a prognostic marker for DTC.

The Relationship between Population T4/TSH Set Point Data and T4/TSH Physiology

Context. Population studies of the distribution of T4/TSH set points suggest a more complex inverse relationship between T4 and TSH than that suggested by physiological studies. The reasons for the similarities and differences between the curves describing these relationships are unresolved. Methods. We subjected the curve, derived from empiric data, describing the TSH suppression response to T4, and the more mathematically derived curve describing the T4 response to TSH, to the different possible models of population variation. The implied consequences of these in terms of generating a population distribution of T4/TSH equilibrium points (a “population curve”) were generated and compared to the empiric population curve. The physiological responses to primary hypothyroidism and hyperthyroidism were incorporated into the analysis. Conclusions. Though the population curve shows a similarly inverse relationship, it is describing a different relationship than the curve describing the suppression of TSH by T4. The population curve is consistent with the physiological studies of the TSH response to T4 and implies a greater interindividual variation in the positive thyroid T4 response to TSH than in the central inhibitory TSH response to T4. The population curve in the dysthyroid states is consistent with known physiological responses to these states.

The role of radioiodine therapy in benign nodular goitre

For treatment of benign nodular goitre the choice usually stands between surgery and (131)I therapy. (131)I therapy, used for 30 years for this condition, leads to a goitre volume reduction of 35-50% within 1-2 years. However, this treatment has limited efficacy if the thyroid (131)I uptake is low or if the goitre is large. Recombinant human TSH (rhTSH)-stimulated (131)I therapy significantly improves goitre reduction, as compared with conventional (131)I therapy without pre-stimulation, and adverse effects are few with rhTSH doses of 0.1 mg or lower. RhTSH-stimulated (131)I therapy reduces the need for additional therapy due to insufficient goitre reduction, but the price is a higher rate of hypothyroidism. Another approach with rhTSH-stimulation is to reduce the administered (131)I activity by a factor that equals the increase in the thyroid (131)I uptake. Using this approach, radiation exposure is considerably reduced while the goitre reduction is similar to that obtained with conventional (131)I therapy.

Thyrotropin in the development and management of differentiated thyroid cancer

Thyrotropin (TSH) is the major regulator and growth factor of the thyroid. TSH may be important in the development of human thyroid cancer, with both suggestive animal models and clinical evidence, although definitive proof is still required. Applications for TSH in thyroid cancer management include TSH stimulation of radioiodine uptake, enhancement of biochemical monitoring through thyroglobulin measurement, and long-term suppression of TSH with supraphysiologic levothyroxine. This review synthesizes current knowledge of TSH in both the development and management of differentiated thyroid cancer.

Long-term efficacy of modified-release recombinant human thyrotropin augmented radioiodine therapy for benign multinodular goiter: results from a multicenter, international, randomized, placebo-controlled, dose-selection study

BACKGROUND

Enhanced reduction of multinodular goiter (MNG) can be achieved by stimulation with recombinant human thyrotropin (rhTSH) before radioiodine ((131)I) therapy. The objective was to compare the long-term efficacy and safety of two low doses of modified release rhTSH (MRrhTSH) in combination with (131)I therapy.

METHODS

In this phase II, single-blinded, placebo-controlled study, 95 patients (57.2 ± 9.6 years old, 85% women, 83% Caucasians) with MNG (median size 96.0 mL; range 31.9-242.2 mL) were randomized to receive placebo (n=32), 0.01 mg MRrhTSH (n=30), or 0.03 mg MRrhTSH (n=33) 24 hours before a calculated (131)I activity. Thyroid volume (TV) and smallest cross-sectional area of trachea (SCAT) were measured (by computed tomography scan) at baseline, six months, and 36 months. Thyroid function and quality of life (QoL) was evaluated at three-month and yearly intervals respectively.

RESULTS

At six months, TV reduction was enhanced in the 0.03 mg MRrhTSH group (32.9% vs. 23.1% in the placebo group; p=0.03) but not in the 0.01 mg MRrhTSH group. At 36 months, the mean percent TV reduction from baseline was 44 ± 12.7% (SD) in the placebo group, 41 ± 21.0% in the 0.01 mg MRrhTSH group, and 53 ± 18.6% in the 0.03 mg MRrhTSH group, with no statistically significant differences among the groups, p=0.105. In the 0.03 mg MRrhTSH group, the subset of patients with basal (131)I uptake <20% had a 24% greater TV reduction at 36 months than the corresponding subset of patients in the placebo group (p=0.01). At 36 months, the largest relative increase in SCAT was observed in the 0.03 mg MRrhTSH group (13.4 ± 23.2%), but this was not statistically different from the increases observed in the placebo or the 0.01 mg MRrhTSH group (p=0.15). Goiter-related symptoms were reduced and QoL improved, without any enhanced benefit from using MRrhTSH. At three years, the prevalence of permanent hypothyroidism was 13%, 33%, and 45% in the placebo, 0.01 mg, and 0.03 mg MRrhTSH groups respectively. The overall safety profile of the study was favorable.

CONCLUSIONS

When used as adjuvant to (131)I, enhanced MNG reduction could not be demonstrated with MRrhTSH doses ≤ 0.03 mg, indicating that the lower threshold for efficacy is around this level.

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.

Radioiodine therapy in benign thyroid diseases: effects, side effects, and factors affecting therapeutic outcome

Radioiodine ((131)I) therapy of benign thyroid diseases was introduced 70 yr ago, and the patients treated since then are probably numbered in the millions. Fifty to 90% of hyperthyroid patients are cured within 1 yr after (131)I therapy. With longer follow-up, permanent hypothyroidism seems inevitable in Graves' disease, whereas this risk is much lower when treating toxic nodular goiter. The side effect causing most concern is the potential induction of ophthalmopathy in predisposed individuals. The response to (131)I therapy is to some extent related to the radiation dose. However, calculation of an exact thyroid dose is error-prone due to imprecise measurement of the (131)I biokinetics, and the importance of internal dosimetric factors, such as the thyroid follicle size, is probably underestimated. Besides these obstacles, several potential confounders interfere with the efficacy of (131)I therapy, and they may even interact mutually and counteract each other. Numerous studies have evaluated the effect of (131)I therapy, but results have been conflicting due to differences in design, sample size, patient selection, and dose calculation. It seems clear that no single factor reliably predicts the outcome from (131)I therapy. The individual radiosensitivity, still poorly defined and impossible to quantify, may be a major determinant of the outcome from (131)I therapy. Above all, the impact of (131)I therapy relies on the iodine-concentrating ability of the thyroid gland. The thyroid (131)I uptake (or retention) can be stimulated in several ways, including dietary iodine restriction and use of lithium. In particular, recombinant human thyrotropin has gained interest because this compound significantly amplifies the effect of (131)I therapy in patients with nontoxic nodular goiter.

Can we interpret serum thyroglobulin results?

Thyroglobulin (Tg) is a tumour marker for differentiated thyroid cancer. Interpretation requires a knowledge of the current thyrotropin (TSH) concentration as secretion is TSH-dependent. While a raised serum Tg may be indicative of residual or recurrent thyroid cancer, trauma to the thyroid (e.g. surgical, biopsy or due to radioiodine treatment) also causes an increase. Tg may be measured when TSH is suppressed and also following recombinant TSH (rhTSH) stimulation. Interpretation of results in pregnancy and in children is discussed. Assay bias and interference by endogenous Tg antibodies (Abs) are the main confounders in the interpretation of results. Although there is an international standard for Tg, there are large differences in results and yet there are few assay-specific clinical decision limits. Patients should therefore be monitored with the same assay. Endogenous TgAbs may cause false-negative interference in immunometric assays and may cause false-positive results in radioimmunoassay. Although the measurement of TgAbs has been advocated for predicting interference, it is now clear that interference can still occur when TgAbs have not been detected, the effect being TgAb-assay-specific. Approaches to identifying those samples where there may be interference are discussed. The laboratory should have a protocol for the investigation of possible interferences and data on the bias of the Tg assay that they use. An appreciation of the clinical uses of the service is required as an understanding by endocrinologists, oncologists and endocrine surgeons of the analytical limitations of the service.

Inability of recombinant human thyrotropin to predict the evolution from subclinical hypothyroidism to overt disease. A pilot study

BACKGROUND

The use of recombinant human TSH (rhTSH) is indicated to evaluate thyroid carcinoma patients. In recent years, some authors have reported that rhTSH could serve as a dynamic test of thyroid reserve. The aim of the present study was to determine whether or not rhTSH can predict the evolution from subclinical hypothyroidism (SH) to overt hypothyroidism.

MATERIALS AND METHODS

Twenty-one women who met the diagnostic criteria of SH were enrolled. All patients received a single dose of rhTSH (0.1 mg). Basal blood samples for TSH, free T4 (fT4), thyroglobulin (Tg), and anti-thyoperoxidase and anti-Tg antibodies were obtained before and 1 day after rhTSH administration. All patients were followed for 2 yr, and blood samples were obtained every 6 months.

RESULTS

Twenty-four hours after rhTSH administration, the TSH level increased to >20 mU/l in 14 patients; the serum peak TSH levels remained <10 mU/l in only 5 patients. On follow-up, 7 women (33%) required L-T4 replacement therapy for overt hypothyroidism or a persistent TSH level >10 mlU/l. None of the parameters analyzed differed significantly between patients who developed overt hypothyroidism from those who had persistent SH.

CONCLUSIONS

The response of thyroid function tests to a single low dose of rhTSH is not useful in identifying those patients with SH who will develop overt hypothyroidism over a 2-yr period.

Radioiodine therapy of benign non-toxic goitre. Potential role of recombinant human TSH

This review provides an update on recombinant human TSH (rh-TSH) augmented radioiodine (¹³¹I) therapy and outlines its potential role in the treatment of symptomatic benign multinodular non-toxic goitre. In some countries, ¹³¹I has been used for three decades to reduce the size of nodular goitres. The feasibility of ¹³¹I therapy depends on an adequate thyroid ¹³¹I uptake. Based on a two-fold increase in thyroid ¹³¹I uptake, superiority studies have convincingly demonstrated that the absorbed thyroid ¹³¹I dose can be increased without increasing the administered ¹³¹I activity, resulting in a 35-56% amplification of goitre reduction at one-year post radioiodine compared to conventional (without rh-TSH) ¹³¹I therapy. Although patient satisfaction is not improved at one-year, this approach facilitates tracheal decompression and is particularly promising in large goitres. The majority of multinodular non-toxic goitre patients may not require amplified goitre reduction. But as an alternative strategy, rh-TSH allows up to 80% reduction of the therapeutic ¹³¹I activity while still achieving goitre reduction comparable to that of conventional ¹³¹I therapy and maintaining high patient satisfaction. The dose-reduction (equality) strategy is attractive in terms of minimizing post-therapeutic restrictions and in reducing the potential risk of radiation-induced malignancy. Adverse effects like temporary thyroid swelling and thyroid hormone excess are to a large extent dose-dependent and generally 0.1mg rh-TSH or less is well tolerated. Based on these results we conclude that rh-TSH augmented ¹³¹I therapy is a promising new therapeutic principle allowing the tailoring of an optimal ¹³¹I therapy on the individual level.

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.

Dose-dependent acute effects of recombinant human TSH (rhTSH) on thyroid size and function: comparison of 0.1, 0.3 and 0.9 mg of rhTSH

CONTEXT

Recombinant human TSH (rhTSH) is used to augment the effect of radioiodine therapy for nontoxic multinodular goitre. Reports of acute thyroid swelling and hyperthyroidism warrant safety studies evaluating whether these side-effects are dose dependent.

OBJECTIVE

To determine the effects on thyroid size and function of various doses of rhTSH.

DESIGN

In nine healthy male volunteers, the effect of placebo, 0.1, 0.3 and 0.9 mg of rhTSH was examined in a paired design including four consecutive study rounds.

MAIN OUTCOME MEASURES

Main outcome measures were evaluated at baseline, 24 h, 48 h, 96 h, 7 days and 28 days after rhTSH and included: Thyroid volume (TV) estimation by planimetric ultrasound, and thyroid function by serum TSH, free T3, free T4 and Tg levels.

RESULTS

Following placebo or 0.1 mg rhTSH, the TV did not change significantly from baseline at any time. At 24 and 48 h after administration of 0.3 mg rhTSH, the TV increased by 37.4 +/- 12.3% (SEM) (P = 0.03) and 45.3 +/- 16.1% (P = 0.05) respectively. After 0.9 mg rhTSH, the TV increased by 23.3 +/- 5.8% (P = 0.008) and 35.5 +/- 18.4% (P = 0.02) respectively. The increase in serum FT3, FT4 and thyroglobulin (Tg) was greater when administering 0.3 mg compared with 0.1 mg (P = 0.02) and when administering 0.9 mg compared with 0.3 mg (P = 0.02). After 0.1 mg rhTSH, the increase in FT3 and Tg was not significantly different from placebo whereas the FT4 increase was significantly higher (P = 0.02 compared with placebo).

CONCLUSIONS

In healthy individuals, rhTSH-induced thyroid swelling and hyperthyroidism is rapid and dose dependent. If valid for patients with goitre, our results suggest that these adverse effects are unlikely to be of clinical significance, following doses of rhTSH of 0.1 mg or less.

A 30-year perspective on radioiodine therapy of benign nontoxic multinodular goiter

PURPOSE OF REVIEW

There is no consensus on the ideal treatment of patients with a benign nontoxic multinodular goiter. In some European countries, (131)I therapy has replaced surgery as the treatment of choice in these patients. Recombinant human thyrotropin (rhTSH) is a very potent stimulator of the thyroid gland and this review focuses on rhTSH-stimulated (131)I therapy.

RECENT FINDINGS

The concept of rhTSH-stimulated (131)I therapy has been tested in several trials during the last 8 years. With this treatment, the goiter reduction is improved by 35-55%, compared with (131)I therapy without rhTSH stimulation. RhTSH prestimulation is particularly beneficial in patients with very large goiters and in those with a low baseline thyroid (131)I uptake. In addition, this therapy facilitates tracheal decompression leading to improved respiratory function. RhTSH-stimulated (131)I therapy results in a higher rate of permanent hypothyroidism, whereas other side-effects are very modest when using a rhTSH dose of 0.1 mg or below.

SUMMARY

RhTSH-stimulated radioiodine therapy of benign nontoxic multinodular goiter is still an off-label use but several trials have shown that this treatment is significantly more effective than (131)I therapy without rhTSH. However, no trial has yet compared (131)I therapy and surgery head-to-head, and future trials should include evaluation of quality of life and cost.

Radioiodine therapy in non-toxic multinodular goitre. The possibility of effect-amplification with recombinant human TSH (rhTSH)

There is no consensus regarding the optimum treatment of benign non-toxic goitre. L-thyroxine suppressive therapy is widely used, but there is poor evidence of its efficacy, and it may have serious adverse effects on health. Surgery is first choice in large goitres or if malignancy is suspected. 131I therapy results in a one-year goitre reduction of around 40% in multinodular goitres, usually with a high degree of patient satisfaction and improvement of the inspiratory capacity. The effect is attenuated with increasing goitre size. The risk of hypothyroidism is 22-58% within 5-8 years. A sufficient thyroid 131I uptake is mandatory for 131I therapy to be feasible and pre-stimulation with recombinant human TSH (rhTSH) increases this considerably. This leads to an increased absorbed thyroid dose by approx.75%, mainly in those patients with the lowest thyroid 131I uptake, and a more homogeneous intrathyroidal isotope distribution. Pre-stimulation with even a small dose of rhTSH seems to allow a reduction of the 131I activity while still achieving a mean goitre reduction of approximately 40% within a year. A significantly lower extrathyroidal radiation is achieved by this approach. With an unchanged 131I activity, rhTSH pre-stimulation improves the goitre reduction by 30-50%. However, this is at the expense of a higher rate of hypothyroidism, cervical pain and transient thyrotoxicosis. Of particular concern is the observation made in healthy persons, that rhTSH results in a transient average thyroid volume increase of 35%. A similar goitre swelling may cause problems in susceptible patients during rhTSH-augmented 131I therapy. Thus, this concept still needs a closer evaluation before routine use.

Recombinant human TSH increases the efficacy of a fixed activity of radioiodine for treatment of multinodular goitre

CONTEXT

High doses of (131)I are usually needed in the treatment of multinodular goitre (MNG) for effective thyroid volume (TV) reduction. Recombinant human thyroid-stimulating hormone (rhTSH) is an adjuvant to enhance (131)I uptake, allowing a decrease in radiation activity and enhancing (131)I efficacy.

OBJECTIVE

To evaluate whether rhTSH increases the efficacy of a fixed activity of (131)I for the treatment of MNG.

DESIGN

Two-year, observational, placebo-controlled study.

SETTING

Patients received 0.1 mg rhTSH (A), 0.005 mg rhTSH (B) or placebo (C). A fixed activity of 1.11 GBq of (131)I was administered 24 h after rhTSH or placebo.

PATIENTS

A total of 28 outpatients (26 females and two males) with MNG.

MEASUREMENTS

TSH, free T4, T3, thyroglobulin (Tg) and TV.

RESULTS

Basal radioactive iodine uptake and TV values were comparable among all groups. After rhTSH or placebo, peak levels of TSH, free T4, T3 and Tg were higher in A than in B or in C (p < 0.05). Hyperthyroidism was observed in A (n = 2), B (n = 6) and C (n = 4). Thyroid enlargement was reported in A (n = 3) and B (n = 6). After 24 months, 10 patients developed hypothyroidism (four in A, three in B and three in C). TV reduction was similar between A and B (37.2 +/- 25.5% vs. 39.3 +/- 27.9%, p = 0.88), but different from the non-significant reduction in C (15.3 +/- 28.3%, p = 0.08).

CONCLUSIONS

Followed by 1.11 GBq, a very low dose of 0.005 mg rhTSH was equally safe and effective as 0.1 mg rhTSH. Both doses increased the efficacy of radioiodine. Adverse events were mild, transient and readily treatable.

Diagnostic and therapeutic use of recombinant human TSH (rhTSH) in differentiated thyroid cancer

Traditionally, withdrawal of thyroid hormone to increase serum levels of thyroid-stimulating hormone (TSH) has been used in patients with differentiated thyroid carcinoma (DTC) to optimize radio-iodine uptake and serum thyroglobulin (Tg) stimulation during follow-up and in preparation for radio-iodine therapy. However, this procedure is associated with signs and symptoms of hypothyroidism which negatively affect the patient's quality of life. Recombinant human thyrotropin (rhTSH) has provided an effective alternative to thyroid hormone withdrawal. After favourable experimental trials in humans, rhTSH obtained regulatory approval in North America and in Europe as a diagnostic tool, and more recently as a preparation for radio-iodine thyroid remnant ablation. Since then, rhTSH has radically changed the diagnostic and therapeutic management of DTC patients. This review will focus on the clinical application of rhTSH in the management of DTC, highlighting current indications and future perspectives.

Optimum recombinant human thyrotropin dose in patients with differentiated thyroid carcinoma and end-stage renal disease

OBJECTIVE

To evaluate serum thyrotropin (TSH) concentrations after conventional (0.9 mg) or half-dose (0.45 mg) administration of recombinant human TSH (rhTSH) injections intramuscularly in patients with end-stage renal disease and differentiated thyroid cancer.

METHODS

In this case series, we administered 2 doses of 0.9-mg rhTSH or 2 doses of 0.45-mg rhTSH to 3 patients with renal failure and differentiated thyroid cancer who were receiving hemodialysis. Basal serum TSH concentrations were assessed while the patients were taking thyroid hormone therapy. Serum TSH was measured on days 2, 3, 5, 8, 10, 14, and 17 of the study. Thyroglobulin and thyroglobulin antibodies were also measured on days 5 and 7. Patients were asked to report any adverse effects.

RESULTS

Patient 1, who received 2 injections of 0.9-mg rhTSH administered on days 1 and 3, had persistently elevated serum TSH levels for approximately 11 days. Peak serum TSH measured on day 5 was 644 mIU/L. Self-limited diarrhea was the only reported adverse effect. Patients 2 and 3 received 0.45 mg of rhTSH on 2 consecutive days (days 1 and 2), and both exhibited persistently elevated serum TSH levels for 12 days. The peak serum TSH values on day 3 were 402 mIU/L in Patient 2 and 386 mIU/L in Patient 3. No adverse events were observed in these 2 patients. Patient 2 received thyrotropin alfa for injection to confirm disease status. Patient 3 also received a radioiodine dose because of presumed persistent disease.

CONCLUSION

High serum TSH levels achieved after conventional and half-dose administration of rhTSH suggest that a dose adjustment might be considered in patients with end-stage renal disease.

Extensions, validation, and clinical applications of a feedback control system simulator of the hypothalamo-pituitary-thyroid axis

BACKGROUND

We upgraded our recent feedback control system (FBCS) simulation model of human thyroid hormone (TH) regulation to include explicit representation of hypothalamic and pituitary dynamics, and updated TH distribution and elimination (D&E) parameters. This new model greatly expands the range of clinical and basic science scenarios explorable by computer simulation.

METHODS

We quantified the model from pharmacokinetic (PK) and physiological human data and validated it comparatively against several independent clinical data sets. We then explored three contemporary clinical issues with the new model: combined triiodothyronine (T(3))/thyroxine (T(4)) versus T(4)-only treatment, parenteral levothyroxine (L-T(4)) administration, and central hypothyroidism.

RESULTS

Combined T(3)/T(4) therapy--In thyroidectomized patients, the L-T(4)-only replacement doses needed to normalize plasma T(3) or average tissue T(3) were 145 microg L-T(4)/day or 165 microg L-T(4)/day, respectively. The combined T(4) + T(3) dosing needed to normalize both plasma and tissue T(3) levels was 105 microg L-T(4) + 9 microg T(3) per day. For all three regimens, simulated mean steady-state plasma thyroid-stimulating hormone (TSH), T(3), and T(4) was within normal ranges (TSH: 0.5-5 mU/L; T(4): 5-12 microg/dL; T(3): 0.8-1.9 ng/mL). Parenteral T(4) administration--800 microg weekly or 400 microg twice weekly normalized average tissue T(3) levels both for subcutaneous (SC) and intramuscular (IM) routes of administration. TSH, T(3), and T(4) levels were maintained within normal ranges for all four of these dosing schemes (1x vs. 2x weekly, SC vs. IM). Central hypothyroidism--We simulated steady-state plasma T(3), T(4), and TSH concentrations in response to varying degrees of central hypothyroidism, reducing TSH secretion from 50% down to 0.1% of normal. Surprisingly, TSH, T(3), and T(4) plasma concentrations remained within normal ranges for TSH secretion as low as 25% of normal.

CONCLUSIONS

Combined T(3)/T(4) treatment--Simulated standard L-T(4)-only therapy was sufficient to renormalize average tissue T(3) levels and maintain normal TSH, T(3), and T(4) plasma levels, supporting adequacy of standard L-T(4)-only treatment. Parenteral T(4) administration-TSH, T(3), and T(4) levels were maintained within normal ranges for all four of these dosing schemes (1x vs. 2x weekly, SC vs. IM), supporting these therapeutic alternatives for patients with compromised L-T(4) gut absorption. Central hypothyroidism--These results highlight how highly nonlinear feedback in the hypothalamic-pituitary-thyroid axis acts to maintain normal hormone levels, even with severely reduced TSH secretion.

An outline concerning the potential use of recombinant human thyrotropin for improving radioiodine therapy of multinodular goiter

Radioiodine ((131)I) treatment for nontoxic and toxic multinodular goiter (MNG) is an alternative therapeutic procedure used especially for patients with contraindication for surgery. Several studies have been conducted in recent years assessing the use of recombinant human TSH (rhTSH) in increasing (131)I uptake in MNGs. This procedure also decreases the activity level of the administered (131)I, changes the distribution of (131)I in the thyroid, lowers the absorption dose, and dramatically reduces the volume of the goiter (50-75% of the baseline volume). A major disadvantage, however, is the induction of hypothyroidism in a relatively large number of patients. A transient increase in thyroid volume and tenderness was noted in the first week of treatment. Also a short period (2-4 weeks) of hyperthyroidism was observed in most patients with potential consequences particularly for the elderly. Still, there has been no evidence to date that the adverse effects outweigh the positive results of using rhTSH. The use of rhTSH in benign goiter disease has not yet been approved worldwide, but its positive activity in MNG is remarkable and promising.

L-T3 preparation for whole-body scintigraphy: a randomized-controlled trial

BACKGROUND

Patients with thyroid cancer often need whole-body scintigraphy (WBS) under TSH stimulation after 4-6 weeks withdrawal from levothyroxine (L-T(4)). Patients often become severely hypothyroid with impaired quality of life. Liothyronine (L-T(3)) substitution is used empirically to prepare patients; however, no data exist to prove its benefit. Objectives To compare the hypothyroid state in patients receiving either placebo or L-T(3) following L-T(4) withdrawal and to evaluate the time needed for adequate TSH elevation in preparation for WBS.

METHODS

At the time of L-T(4) withdrawal, patients were randomized to receive L-T(3 )(50 microg qd) or placebo for 3 weeks, after which treatment was stopped. A validated evaluation of hypothyroidism (Billewicz score) was administered in a double-blind fashion every 2 weeks until the WBS. TSH, fT(4) and fT(3) were measured weekly.

RESULTS

A total of 20 patients were randomized between September 2003 and May 2005. There was no difference in the Billewicz score at any time between the two groups. Before WBS, both groups were profoundly hypothyroid. TSH at time of WBS was similar in both groups. The time needed to reach a TSH level of more than 30 mUI/l was longer in L-T(3) group (mean +/- SD: 32 +/- 4 days vs. 17 +/- 9 days in placebo group, P = 0.006).

CONCLUSION

Preparation for WBS with L-T(3) does not prevent profound hypothyroidism and delays TSH elevation required for WBS. L-T(4) withdrawal alone for 2-3 weeks is simpler and sufficient to allow TSH to reach a level of more than 30 mUI/l in the majority of patients without increasing morbidity from hypothyroidism.

How the availability of recombinant human TSH has changed the management of patients who have thyroid cancer

Recombinant human TSH (rhTSH) is used in patients who have had surgery for thyroid cancer but are at low risk of recurrence. The rhTSH is used for the preparation of postoperative administration of 3.7 GBq (100 mCi) of radioiodine for thyroid-remnant ablation and for the determination of serum thyroglobulin levels during follow-up. In these two conditions, the efficiencies of levothyroxine withdrawal and rhTSH administration are similar; however, rhTSH can be administered during levothyroxine treatment, and its use avoids the hypothyroid period induced by levothyroxine withdrawal, reduces whole body exposure after radioiodine administration, avoids potential morbidity and maintains a better quality of life compared with hormone withdrawal.

Peripheral blood levels of thyroglobulin mRNA and serum thyroglobulin concentrations after radioiodine ablation of multinodular goiter with or without pre-treatment with recombinant human thyrotropin

We investigated the effect of therapeutic doses of radioiodine (RAI) on peripheral serum messenger thyroglobulin RNA (Tg mRNA) and serum thyroglobulin (sTg) in patients with multinodular goiter (MNG) preceded or not by treatment with recombinant human TSH (rhTSH). Fourteen patients with large MNG (91-542 ml) received RAI (550-2960 MBq). Half of the patients received 0.45 mg of rhTSH prior to the treatment (RAI+rhTSH group) and half did not (RAI group). Patients' blood samples were collected before and 24, 48, and 72 h; 7 and 30 days; and 6, 9, and 12 months after RAI treatment. Serum Tg was measured by immunoradiometric assay, serum anti-Tg by radioimmunoassay, and quantification of circulating Tg mRNA was performed by real-time PCR. The shrinkage of MNG volume was documented by serial computed tomography (CT) scans before, 6 and 12 months after RAI. Peak Tg mRNA and sTg were reached earlier in the RAI+rhTSH group (24 h and 48 h) than in the RAI group (7 days). Both declined after the peak and the lowest levels were observed at 12 months. The mean reduction of the thyroid volume was 19.8% (RAI group) and 30.3% (RAI+rhTSH group) at 6 months (ns) and 32.8% RAI and 52.5% (RAI+rhTSH group) at 12 months (p<0.05). After RAI treatment there was a significant and positive correlation between goiter volume and sTg only in the RAI group (r=0.7; p=0.032). Serum anti-Tg had a transitory and relatively small elevation in 3 and 2 patients, respectively, in the RAI and RAI+rhTSH groups. We concluded that after RAI ablation of MNG there is a rapid release of Tg into the serum possibly from the colloid, which is followed by an elevation of serum Tg mRNA that may be due to an increased release of follicular cells into the blood stream. Both phenomena are enhanced by the use of rhTSH before RAI treatment as a consequence of a more effective and prolonged radiation exposure of the thyroid follicles.

Management of differentiated thyroid carcinoma with radioiodine and recombinant human TSH

Recombinant human TSH (rhTSH) brought revolutionary change in the management of patients with differentiated thyroid cancer since it was first approved for clinical use in the United States and Europe. Follow-up management of differentiated thyroid cancer is based on the detection of recurrent or residual cancer, traditionally achieved by measurement of serum thyroglobulin level and various imaging techniques including 131I whole body scan. Previously, TSH stimulation was achieved only by induction of hypothyroidism following withdrawal of thyroid hormone. However, hypothyroidism is uncomfortable and is association with a reduction in quality of life. RhTSH can provide elevated TSH without making patients hypothyroid. In the United States and Europe, rhTSH is approved for use only in monitoring of differentiated thyroid cancer. In this article, we reviewed the role of rhTSH in the diagnosis and management of differentiated thyroid cancer.

Transient goiter enlargement after administration of 0.3 mg of recombinant human thyrotropin in patients with benign nontoxic nodular goiter: a randomized, double-blind, crossover trial

BACKGROUND

Recombinant human (rh) TSH, in doses from 0.01 to 0.9 mg, has been used to augment the effect of radioiodine ((131)I) therapy in patients with a benign nontoxic nodular goiter. Transient thyroid enlargement and thyrotoxicosis may be seen following (131)I therapy.

AIM

The aim of the study was to investigate whether rhTSH per se causes goiter enlargement, until now an issue evaluated only in healthy nongoitrous subjects.

METHODS

In random order, 10 patients with nontoxic nodular goiter [mean 39.8 +/- 20.5 (sd) ml] received either 0.3 mg rhTSH or isotonic saline in a double-blinded crossover design. Thyroid volume (by ultrasound) and function were closely monitored during the following 28 d.

RESULTS

Saline injection did not affect thyroid function or size. After rhTSH, median serum TSH increased from baseline 0.97 mU/liter (range 0.39-1.56) to 37.0 mU/liter (range 18.5-55.0) at 24 h (P < 0.01), with a subsequent decline to subnormal levels at d 7. Mean free T(4) and free T(3) increased significantly from baseline to a maximum at 48 h. Twenty-four hours after rhTSH, the mean goiter volume was significantly increased by 9.8 +/- 2.3% (sem) (P = 0.01) and after 48 h by 24.0 +/- 5.1% (P = 0.002). The goiter enlargement had reverted at d 7. Nine patients had symptoms of hyperthyroidism and/or cervical compression after rhTSH, as opposed to one during placebo treatment (P < 0.02).

CONCLUSIONS

A transient average goiter enlargement of up to 24% is seen after 0.3 mg rhTSH. This may lead to a significant cervical compression when used for augmentation of (131)I therapy in patients with goiter. The use of lower doses of rhTSH needs to be explored.

Use of recombinant human thyroid-stimulating hormone in the management of well-differentiated thyroid cancer

Recombinant human (rh) thyroid-stimulating hormone (TSH) has changed the care of patients with well-differentiated thyroid cancer (DTC). Traditionally, thyroid hormone withdrawal has been used to increase TSH concentrations for optimising trapping and retention of radioiodine for thyroid remnant ablation and for diagnostic procedures (measurement of thyroglobulin and whole body scan) used in the follow-up of patients with DTC. The resulting hypothyroidism is, however, accompanied by substantial morbidity. rhTSH is an effective and safe alternative to thyroid hormone withdrawal for follow-up of DTC. Its ability to detect persistent or recurrent disease is similar to that of thyroid hormone withdrawal. At the present time, rhTSH is approved for diagnostic monitoring of patients with DTC as well as for pretherapeutic stimulation in low-risk patients for remnant ablation with 100 mCi (131)I (in the EU). In addition, rhTSH has potential for use in facilitating the treatment of metastasis in patients with DTC and in patients with non-toxic nodular goiter; however, more clinical trials are needed to confirm its use in these situations.

Clinical uses of recombinant human thyrotropin

Recombinant human thyroid-stimulating hormone (rhTSH), used to enhance diagnostic radioiodine whole body scanning and thyroglobulin testing, has dramatically altered the management of patients with thyroid cancer. Withdrawal from thyroid hormone suppression therapy and subsequent hypothyroidism is no longer the only safe and effective method for thyroid cancer surveillance. Currently, rhTSH is only approved for the monitoring of low-risk patients with well-differentiated thyroid cancer and radioactive iodine administration, in selected cases. Additional applications of rhTSH include enhancing the sensitivity of positron emission tomography in thyroid cancer, the management of multinodular goiter, and dynamic testing of thyroid reserve. The diagnostic and therapeutic role of rhTSH in these areas is discussed in this review.