Nelson et al1 report that the development of hypothyroidism in patients with advanced head and neck cancer may be associated with improved survival and highlight the issue of L-thyroxine supplementation in patients diagnosed as having chemical hypothyroidism. Because thyroid hormone supplementation is invariably prescribed for chemical but clinically asymptomatic hypothyroidism, as was the case in the patients in Nelson and colleagues' retrospective study, it is of note that the American Thyroid Association2 consensus statement advises that thyroid hormone replacement therapy may not be indicated in subclinical hypothyroidism, ie, in asymptomatic individuals with a serum thyroid-stimulating hormone (TSH) concentration that is mildly elevated (up to 10.0 mIU/L). 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 thyroid hormone (L-thyroxine, thyroxine, and triiodothyronine) in the growth of certain solid tumors.
Hercbergs A, Davis P. Hypothyroidism in the Patient With Cancer: How Much Thyroid Supplementation Is “Safe”?. Arch Otolaryngol Head Neck Surg. 2007;133(6):625-626. doi:10.1001/archotol.133.6.625-c