Is prophylactic anti-resorptive therapy required in thyroid cancer patients receiving TSH-suppressive treatment with thyroxine?

Excerpt

Thyroid stimulating hormone (TSH) acts via its G-protein coupled receptor (TSHR) to stimulate proliferation of thyroid follicular cells, iodine uptake, and the synthesis and secretion of thyroglobulin, thyroxine (T4) and 3,5,3′-l-triiodothyronine (T3). Thyroid cancer cells express the TSHR and, following initial management with surgery and radioiodine, retrospective studies indicate that treatment of patients with doses of T4 that suppress the circulating TSH concentration reduces cancer recurrence and disease-specific mortality. A prospective non-randomized study further indicates that a lesser degree of TSH suppression is an independent predictor of disease progression in patients at high risk of disease recurrence [1]. Nevertheless, in the majority of patients at low risk following initial treatment, the benefit of TSH suppression is questionable as it may result in a wide range of adverse effects particularly affecting the cardiovascular system and skeleton [2]. Thus, the most recent guidelines for management of differentiated thyroid cancer advocate stratification of TSH suppression according to the risk of recurrent disease [3, 4]. In patients with an excellent response to initial treatment and at low risk, TSH suppression is not indicated and the concentration should be maintained in the low-normal range between 0.3 and 2.0 mU/L. In those with an indeterminate response and at intermediate risk, the T4 dose should be adjusted to maintain TSH between 0.1 and 0.5 mU/L for a period of 5–10 years. In patients with an incomplete response and at high risk of recurrence, TSH should be suppressed below 0.1 mU/L indefinitely. Furthermore, TSH suppression below 0.1 mU/L for 5–10 years followed by clinical re-evaluation is recommended for historical patients who did not have dynamic risk stratification after initial treatment. Thus, although the vast majority of patients with thyroid cancer respond well to initial treatment and do not require TSH suppression because of a low risk of disease recurrence [3, 4], there remain significant numbers of patients in long-term follow-up who do. …