Exogenous thyrotropin improves renal function in euthyroid patients, while serum creatinine levels are increased in hypothyroidism

Recombinant or endogenous thyroid-stimulating hormone for radioactive iodine therapy in thyroid cancer: state of knowledge and current controversies

For patients undergoing radioiodine therapy (RIT) of differentiated thyroid carcinoma (DTC), thyroid-stimulating hormone (TSH) stimulation prior to RIT can be achieved using thyroid hormone withdrawal (THW) or administration of recombinant human TSH (rhTSH). As THW can lead to nausea, headaches, vomiting, fatigue, and dizziness secondary to transient acute hypothyroidism, rhTSH could be a good alternative. Recombinant human TSH has been administered in patients in order to stimulate TSH for RIT since 2005. According to the Martinique criteria formulated by the leading professional societies involved in care of patients with DTC, rhTSH can be applied in 3 settings: for remnant ablation, adjuvant treatment, and treatment of known disease. Numerous studies have investigated the effects of rhTSH as a method of TSH stimulation on the thyroid cell, the systemic effects, biokinetics, and clinical outcomes; however, no consensus has been reached about many aspects of its potential use. Recombinant human TSH is able to stimulate sufficient TSH levels (>30 mIU L-1) and is hypothesized to decrease risks of tumor cell proliferation. As rhTSH-use avoids the transiently impaired renal function associated with THW, radioiodine excretion is faster with the former, leading to a lower iodine-131 uptake and a difference in fractional remnant uptake, effective half-life, mean residence time, and dose to the blood. Differences between rhTSH and THW were observed in radioiodine genotoxic effects and endothelial-dependent vasodilation and inflammation. For thyroid remnant ablation, THW and rhTSH lead to similar remnant ablation rates. For adjuvant therapy and treatment of known disease, insufficient trials have been conducted and future prospective studies are recommended. The current review provides a state-of-the-science overview on the issues and debates surrounding TSH stimulation through either rhTSH adminsitration orendogenous TSH production after levothyroxin withdrawal.

Subclinical Hypothyroidism in Advanced Chronic Kidney Disease Patients: Prevalence and Associated Factors

Introduction

Renal function and thyroid metabolism are tightly related. However, evidence about subclinical hypothyroidism prevalence in patients with chronic kidney disease and its related factors is scarce.

Objectives

Our aim is to analyze subclinical hypothyroidism prevalence and its related factors in patients with advanced chronic kidney disease. Materials and methods. Nondialysis-dependent patients with chronic kidney disease at stages 3 to 5 were included. Other inclusion criteria were age above 18 years and clinical stability. Patients with diagnosed thyroid illnesses were excluded. Subclinical hypothyroidism was defined as thyroid stimulating hormone (TSH) > 5.3 mU/L, with free thyroxine 4 (FT4) between 0.54 and 1.24 ng/dl. Filiation data, comorbidities, and routine blood and urine test results were registered.

Results

A total of 299 patients were included. Of them, 184 (61.5%) were men. The mean age was 71 ± 13 years old. The mean glomerular filtration rate (CKD-EPI) was 22 ± 9 ml/min/1.73 m². According to chronic kidney disease stages, global distribution of patients was as follows: Stage 3, 67 patients (22.4%); Stage 4, 155 patients (51.8%); and Stage 5, 77 patients (25.8%). We found subclinical hypothyroidism in 54 (18.1%) patients. According to chronic kidney disease stages, distribution of affected patients was as follows: Stage 3, 9 patients (13%); Stage 4, 25 patients (16.1%); and Stage 5, 20 patients (26%). Differences among stages were statistically significant. By univariate analysis, factors related with subclinical hypothyroidism were as follows: age RR 1.048 (95% CI 1.019–1.078; p=0.001), hypertension RR 2.705 (95% CI 1.026–7.130; p=0.04), glomerular filtration rate RR 0.962 (95% CI 0.929–0.996; p=0.03), and proteinuria higher than 1 gram/day RR 2.387 (95% CI 1.303–4.374; p=0.005). By multivariate analysis adjusted by age, hypertension, glomerular filtration rate, proteinuria, diabetes, and cardiovascular disease history, only age RR 1.016 (95% CI 1.009–1.028; p=0.04) and glomerular filtration rate RR 0.963 (95% CI 0.930–0.997; p=0.03) preserved their independent association with subclinical hypothyroidism.

Conclusions

Subclinical hypothyroidism prevalence in patients with chronic kidney disease is high and increases with renal disease severity. Factors independently related to subclinical hypothyroidism are age and glomerular filtration rate.

Adjustment of the iodine ICRP population pharmacokinetic model for the use in thyroid cancer patients after thyroidectomy

Biokinetic models developed for healthy humans are not appropriate to describe biokinetics in thyroid cancer patients following thyroidectomy. The aim of this study was to adjust the population model for iodine proposed by the International Commission on Radiological Protection (ICRP) for the use in these patients. Rate constants of the ICRP publication 128 model for iodine were adjusted using the population modelling software package Monolix to describe activity retention in whole-body, thyroid, blood and protein-bound iodine observed in 23 patients. The new set of rate constants was compared to the four uptake scenarios proposed in ICRP publication 128. Flow from the inorganic iodide in blood compartment into the first thyroid compartment decreases to 0.15 d^-1compared to a value of 7.27 d^-1for the ICRP publication 128 model with a medium uptake. The transfer from first to second thyroid compartments and the outflow from the second thyroid compartment increases. An increased turnover rate of extrathyroidal organic iodine is observed. The rate constant from inorganic iodide in blood to kidney was also adjusted. Overall a good agreement was found between the adjusted model and the activity retention in thyroid cancer patients. The adjustment of population pharmacokinetic models to describe the biokinetic properties of specific patient populations for therapeutic radiopharmaceuticals is essential to capture the changes in biokinetics. The proposed set of rate constants for the established ICRP publication 128 model can be used to more accurately assess radiation protection requirements for the treatment of thyroid cancer patients using radioiodine.

The Role of Hormones and Trophic Factors as Components of Preservation Solutions in Protection of Renal Function before Transplantation: A Review of the Literature

Transplantation is currently a routine method for treating end-stage organ failure. In recent years, there has been some progress in the development of an optimal composition of organ preservation solutions, improving the vital functions of the organ and allowing to extend its storage period until implantation into the recipient. Optimizations are mostly based on commercial solutions, routinely used to store grafts intended for transplantation. The paper reviews hormones with a potential nephroprotective effect, which were used to modify the composition of renal perfusion and preservation solutions. Their effectiveness as ingredients of preservation solutions was analysed based on a literature review. Hormones and trophic factors are innovative preservation solution supplements. They have a pleiotropic effect and affect normal renal function. The expression of receptors for melatonin, prolactin, thyrotropin, corticotropin, prostaglandin E1 and trophic factors was confirmed in the kidneys, which suggests that they are a promising therapeutic target for renal IR (ischemia-reperfusion) injury. They can have anti-inflammatory, antioxidant and anti-apoptotic effects, limiting IR injury.

Recombinant Human Thyrotropin Worsens Renal Cortical Perfusion and Renal Function in Patients After Total Thyroidectomy Due to Differentiated Thyroid Cancer

Background: Although thyrotropin (TSH) receptors are found in many nonthyroid tissues, we know little about the direct action of TSH on these receptors. Patients after total thyroidectomy for differentiated thyroid cancer (DTC) provide an interesting model for studying this issue. The administration of exogenous TSH in patients with an established thyroid state on levothyroxine (LT4) treatment allows us to study the effect of elevated TSH concentrations independent of thyroid status on the function of various organs, including the kidneys. The aim of this study was to assess the effects of the administration of recombinant human TSH (rhTSH) on renal perfusion and glomerular filtration in this group of patients. Methods: The study included 24 patients after total thyroidectomy due to DTC, without concomitant diseases, receiving only LT4 who qualified for radioiodine treatment (RIT). For two consecutive days, the patients received rhTSH and subsequently the RIT. Clinical and biochemical evaluation of thyroid and renal function was carried out before and 24 hours after the second dose of rhTSH and before the RIT. On the sixth day of hospitalization, the patients' glomerular filtration rate was re-evaluated. Kidney perfusion was assessed using color Doppler ultrasound imaging before and 24 hours after the second dose of rhTSH and before the RIT. Results: The administration of rhTSH to patients after total thyroidectomy due to DTC caused significant deterioration of renal perfusion after the second dose of rhTSH before the RIT, which was followed by a significant reduction in glomerular filtration. Furthermore, rhTSH did not significantly affect the hemodynamic parameters that could worsen renal function. Conclusions: This study indicates that TSH alone, independent of thyroid hormone concentrations, can influence renal perfusion and renal function.

Quantitative bias analysis of the association between subclinical thyroid disease and two perfluoroalkyl substances in a single study

Exposure to perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) has been associated with the occurrence of thyroid disease in some epidemiologic studies. We hypothesized that in a specific epidemiologic study based on the National Health and Nutrition Examination Survey, the association of subclinical thyroid disease with serum concentration of PFOA and PFOS was due to reverse causality. Thyroid hormone affects glomerular filtration, which in turn affects excretion of PFOA and PFOS. We evaluated this by linking a model of thyroid disease status over the lifetime to physiologically based pharmacokinetic models of PFOA and PFOS. Using Monte Carlo methods, we simulated the target study population and analyzed the data using multivariable logistic regression. The target and simulated populations were similar with respect to age, estimated glomerular filtration rate, serum concentrations of PFOA and PFOS, and prevalence of subclinical thyroid disease. Our findings suggest that in the target study the associations with subclinical hypothyroidism were overstated and the results for subclinical hyperthyroidism were, in general, understated. For example, for subclinical hypothyroidism in men, the reported odds ratio per ln(PFOS) increase was 1.98 (95% CI 1.19-3.28), whereas in the simulated data the bias due to reverse causality gave an odds ratio of 1.19 (1.16-1.23). Our results provide evidence of bias due to reverse causality in a specific cross-sectional study of subclinical thyroid disease with exposure to PFOA and PFOS among adults.

Long-term outcomes of renal function after radioactive iodine therapy for thyroid cancer according to preparation method: thyroid hormone withdrawal vs. recombinant human thyrotropin

PURPOSE

Long-term effects of iatrogenic hypothyroidism on renal function from thyroid hormone withdrawal during radioactive iodine therapy (RAIT) have not been studied, especially in subjects with mildly impaired renal function. We compared renal function in thyroid cancer subjects according to preparation method of either thyroid hormone withdrawal (THW) or injection of recombinant human thyrotropin (rhTSH).

METHODS

This retrospective study enrolled 241 thyroidectomized patients (rhTSH group, n = 87 and THW group, n = 154). Changes in glomerular filtration rate (GFR) were measured prior to surgery, at the time of RAIT, and during a regular follow-up at least one year after RAIT.

RESULTS

Baseline renal function was comparable between the rhTSH group and the THW group (91.4 mL/min/1.73 m² vs. 92.4 mL/min/1.73 m²). At the time of RAIT, GFR was significantly decreased in the THW group (70.6 mL/min/1.73 m², -23.6%), whereas renal function was preserved in the rhTSH group (85.4 mL/min/1.73 m², -6.6%). In the THW group, renal function was fully recovered within 6 months after RAIT and was maintained up to 24 months, even in subjects with baseline GFR less than 90 mL/min/1.73 m².

CONCLUSIONS

THW for RAIT preparation induced considerable reduction in renal function, but this change was transient. In contrast, injection of rhTSH did not decrease renal function, making it a good option for RAIT preparation for subjects with renal dysfunction.

Determination of effective half-life of 131I in patients with differentiated thyroid carcinoma: comparison of cystatin C and creatinine-based estimation of renal function

PURPOSE

Renal function and effective half-life (t_1/2,eff) of I-131 have not been fully elucidated in patients undergoing radioiodine therapy (RAIT) for differentiated thyroid cancer (DTC). Aim of the present analysis was to evaluate the potential of cystatin C-based estimated glomerular filtration rate (eGFR_CysC) in comparison to conventional creatinine (eGFR_Crea) and to verify which methods to determine t_1/2,eff are most accurate to predict t_1/2,eff.

METHODS

Forty-eight patients receiving whole-body I-131-scintigraphy were included. eGFR_CysC was compared to eGFR_Crea with regard to accuracy of t_1/2,eff prediction. Three different methods (i.e. blood-based, gamma camera-based and probe-based) and two protocols with either three (short period,SP; up to 42 h) or four (long period,LP; up to 114 h) time points were compared using the Akaike's information criterion.

RESULTS

The eGFR_CysC measurement is more likely than eGFR_Crea in predicting the t_1/2,eff. High correlation coefficients were found between t_1/2,eff assessed by gamma camera and probe measurements and blood-based determination revealed lower values. Patients with normal eGFR showed higher values of t_1/2,eff of LP compared to SP.

CONCLUSIONS

eGFR_CysC should be included in further study protocols. As camera and probe measurements lead to almost superimposable results, one of the methods is expendable. Blood-based results of t_1/2,eff were lower, presumably due to unspecific iodine retention, whereas the lower correlation with renal function may be caused by individual differences in intestinal iodine resorption. SP-protocols up to 42 h after I-131 administration are sufficient to determine t_1/2,eff. Further studies are necessary for specific recommendations regarding I-131 activity reduction during RAIT in patients with DTC and renal insufficiency.

Prediction of iodine-131 biokinetics and radiation doses from therapy on the basis of tracer studies: an important question for therapy planning in nuclear medicine

OBJECTIVES

This study aimed to present a comparison of iodine-131 (I) biokinetics and radiation doses to red-marrow (rm) and whole-body (wb), following the administration of tracer and therapeutic activities, as a means of confirming whether I clearance and radiation doses for therapy procedures can be predicted by tracer activities.

METHODS

Eleven differentiated thyroid cancer patients were followed after receiving tracer and therapeutic I activity. Whole-body I clearance was estimated using radiation detectors and OLINDA/EXM software was used to calculate radiation doses to rm and wb.

RESULTS AND DISCUSSION

Tracer I activity of 86 (±14) MBq and therapeutic activity of 8.04 (±1.18) GBq were administered to patients, thereby producing an average wb I effective half-time and residence time of, respectively, 13.51 (±4.05) and 23.13 (±5.98) h for tracer activities and 13.32 (±3.38) and 19.63 (±4.77) h for therapy. Radiation doses to rm and wb were, respectively, 0.0467 (±0.0208) and 0.0589 (±0.0207) mGy/MBq in tracer studies and 0.0396 (±0.0169) and 0.0500 (±0.0163) mGy/MBq in therapy. Although the differences were not considered statistically significant between averages, those between the values of effective half-times (P=0.906), residence times (P=0.145), and radiation doses to rm (P=0.393) and to wb (P=0.272), from tracer and therapy procedures, large differences of up to 80% in wb I clearance, and up to 50% in radiation doses were observed when patients were analyzed individually, thus impacting on the total amount of I activity calculated to be safe for application in individual therapy.

CONCLUSION

I biokinetics and radiation doses to rm and wb in therapy procedures are well predicted by diagnostic activities when average values of a group of patients are compared. Nonetheless, when patients are analyzed individually, significant differences may be encountered, thus implying that nuclear medicine therapy-planning requires due consideration of changes in individual patient-body status from initial tracer to final therapy procedures to thus provide appropriate adjustments in therapeutic activities.

Effects of Thyroid Hormone Withdrawal and Recombinant Human Thyrotropin on Glomerular Filtration Rate During Radioiodine Therapy for Well-Differentiated Thyroid Cancer

BACKGROUND

Renal function is related to thyroid hormonal status, and glomerular filtration rate (GFR) seems to be impaired in patients with hypothyroidism. The aim of this work was to evaluate quantitatively the effect of hypothyroidism on GFR using a (51)Cr-EDTA radioisotope assay.

METHODS

Twenty-eight patients without known renal disease or dysfunction who had been referred for radioiodine therapy (RIT) after total thyroidectomy were enrolled in this study and divided into two groups. Group A underwent thyroid hormone withdrawal (THW) resulting in hypothyroidism, while group B underwent recombinant human thyrotropin (rhTSH) stimulation and hence remained euthyroid. GFR was assessed by (51)Cr-EDTA before and after THW or rhTSH.

RESULTS

No clinical differences were observed between the two groups. The mean ± SD GFRs were 94 ± 19 mL/min/1.73 m(2) before THW and 76 ± 16 mL/min/1.73 m(2) after THW for group A (p = 0.009), and 91 ± 18 mL/min/1.73 m(2) before rhTSH and 93 ± 15 mL/min/1.73 m(2) after rhTSH for group B (p = 0.613). The percent decrease in GFR during hypothyroidism is approximately 18-22%.

CONCLUSION

GFR decreases in patients with normal kidney function during THW for RIT, and rhTSH preserves GFR in these patients. This GFR impairment following thyroidectomy is related to hypothyroidism due to a significant reduction in thyroid hormone levels and is not due to a rise in the TSH level.