Management of hypothyroidism after radiotherapy for nasopharyngeal carcinoma

Excerpt

A recent study in Medical Oncology advises that “Early thyroid hormone replacement therapy in patients becoming hypothyroid is important.…” [1]. We would like to respond to this statement with a caveat. Concerns regarding thyroid hormone (TH) replacement in such patients have recently been published [2, 3]. A guideline paper by the American Thyroid Association (ATA) [4] advises withholding TH replacement in asymptomatic, chemically hypothyroid patients (TSH between 5 and 10 μU/mL). In fact, some patients with TSH levels even >10 have little-to-no symptoms and, therefore, do not necessarily need TH supplementation. This consensus position may be especially relevant for individuals with a prior or current cancer diagnosis in view of the growing body of evidence that supports a permissive role for TH (l-thyroxine, [T4] and triiodothyronine, [T3]) in the growth of certain epithelial tumors. A cell membrane receptor specifically for TH [l-thyroxine] on integrin avβ3 has been identified that mediates the effect of that hormone in vitro on cancer cell proliferation, on the growth of human breast cancer xenographs, as well as on the induction of tumor angiogenesis, possibly supporting tumor growth [5‐7]. …