FMO5 and Primary hypothyroidism: An alternative explanation to be excluded could be that in the setting of primary hypothyroidism caused by a failure of secreted TG (despite active thyroid hormone synthesis machinery, ref. 12, including NADPH oxidase-mediated H2O2 generation, refs. 39, 40, and thyroid peroxidase-mediated iodination, ref. 17), thyroid cell death might emerge as a secondary consequence of these potentially cytotoxic TSH-stimulated enzymatic activities, as has been previously suggested (41).