Stimulation test in the follow-up of thyroid cancer: Plasma rhTSH levels are dependent on body weight, not endogenously stimulated TSH values

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.

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.

Absence of thyrotropin-induced increase in leptin levels in patients with history of differentiated thyroid carcinoma undergoing recombinant human thyrotropin testing

BACKGROUND

Some extra-thyroid effects of TSH have been described in vitro and in vivo. TSH has recently been suggested to induce interleukin-6 secretion by adipocytes. Leptin is the main protein secreted by adipose tissue.

OBJECTIVE

The aim of our study was to evaluate the acute effect of the recombinant human TSH (rhTSH)-induced TSH surge on serum leptin levels in thyroidectomized patients undergoing levothyroxine (L-T4) suppressive therapy for differentiated thyroid carcinoma (DTC).

DESIGN

A cohort of 15 female DTC patients was evaluated. Standard rhTSH testing was performed. Leptin, TSH, thyroid hormones, and thyroglobulin were measured before and 3, 6, and 9 days after rhTSH testing. Some metabolic parameters were also evaluated at the baseline.

RESULTS

Baseline leptin levels were 12.2+/-3.2 microg/l. Only body mass index (BMI) correlated significantly (p<0.05) with leptin levels. After rhTSH administration, TSH levels increased significantly (p<0.001), while thyroid hormones remained unchanged. Twenty hours after the last rhTSH administration, leptin (11.8+/-3.0 microg/l) levels were unchanged. The maximal TSH level was negatively related with BMI (p<0.05), but no correlation between maximal TSH and leptin levels after rhTSH was noted.

CONCLUSIONS

Our in vivo experimental model suggests that an acute TSH increase after rhTSH testing is ineffective in changing circulating leptin levels.