Diabetes impairs thyroid function by changing thyroid-stimulating hormone (TSH) levels and by disturbing the conversion of thyroxine (T4) to triiodothyronine (T3) in peripheral tissues [27]. In euthyroid diabetic patients, the nocturnal TSH peak can be absent or diminished and the TSH response to thyrotropin-releasing hormone (TRH) can be compromised. This evidence concerns the gene TRH and diabetes mellitus.