Area under the curve of TSH after levothyroxine withdrawal versus administration of recombinant human TSH (rhTSH): possible implications for tumor growth

Abstract

OBJECTIVE: The levothyroxine withdrawal (L-T4) for some weeks results in prolonged exposure to elevated TSH. In contrast, administration of recombinant human TSH (rhTSH) promotes a short period of hyperthyrotropinemia. The objective of this study was to compare the area under the curve (AUC) of TSH obtained after L-T4 withdrawal versus administration of rhTSH. METHODS: Thirty patients received 0.9 mg rhTSH for two consecutive days, and 64 were prepared by L-T4 withdrawal for four weeks, with the latter being reintroduced 48 hour after 131I. Measurement of TSH were performed before the first rhTSH ampoule; immediately before and seven and 14 days after 131I; before L-T4 withdrawal; and, weekly, up to two months after 131I. RESULTS: The AUC obtained after rhTSH was 4.6 times smaller than that obtained after L-T4 withdrawal (532 versus 2,423 mIU/L per day). It should be emphasized that, on average, in the latter group, 58.5% of the AUC corresponded to the period after reintroduction of hormone therapy. CONCLUSIONS: Surprising difference in the TSH AUC was demonstrated between rhTSH administration versus L-T4 withdrawal.

Incidence and implications of negative serum thyroglobulin but positive I‐131 whole‐body scans in patients with well‐differentiated thyroid cancer prepared with rhTSH or thyroid hormone withdrawal

“…This may possibly relate to differences in the physiology of Tg stimulation between the two methods. Preparation with rhTSH results in a rapid peak and drop off in TSH levels over a 5‐day period, whereas preparation with thyroid hormone withdrawal results in a more prolonged and sustained period of elevated TSH levels over several weeks which is associated with approximately twice the peak concentration of Tg compared to preparation with rhTSH 21–23 …”

Thyroid nodules and differentiated thyroid cancer: update on the Brazilian consensus

“…Even when none such condition is present, recombinant TSH is preferable when it is available in patients with complete tumor resection and no apparent metastasis after thyroidectomy because it is known to be efficacious in such cases (108)(109)(110)(111)(112). Furthermore, recombinant TSH exhibits advantages over discontinuation of T4: the quality of life of the patients is not affected; it eliminates the symptoms and eventual risk of hypothyroidism; and it is associated with shorter leaves of absence, less extrathyroidal radiation, and shorter exposure to high TSH levels (103,108,109,111,113). In the remainder of patients (incomplete tumor resection or persistent metastases), discontinuation of T4 over 3 or 4 weeks is still the most proper indication in the absence of clinical contraindications.…”

“…I ablation/therapy is preceded by discontinuation of T4, hormone replacement must be restarted early, i.e., 48 hours after the administration of RAI, and at the full dose to promote rapid TSH reduction (113).…”

Response Prediction of Altered Thyroglobulin Levels After Radioactive Iodine Therapy Aided by Recombinant Human Thyrotropin in Patients with Differentiated Thyroid Cancer

“…I-131 is usually administered on the day after the second injection of rhTSH, according to the conventional schedule. Serum Tg levels should be measured 72 h after the final injection of rhTSH, which corresponds to peak serum Tg levels [9]. rhTSH-stimulated Tg has been studied as a prognostic marker in DTC patients [7,8].…”

“…In DTC patients who received RAI therapy prepared with recombinant human thyrotropin (rhTSH), stimulated Tg measured before or after RAI therapy (72 h after the final injection of rhTSH) could be also used as a prognostic marker [7,8]. However, rhTSH-stimulated Tg levels before RAI therapy could be underestimated because 72 h after the second injection of rhTSH corresponds to peak serum Tg levels [9]. rhTSH-stimulated Tg levels checked 72 h after the second injection could be overestimated through the addition of Tg released from damaged residual thyroid tissues after RAIinduced cellular injury [10][11][12][13].…”