What is more, such factors as medicines taken (e.g., iron, angiotensin converting enzyme inhibitors (ACE-I), angiotensin receptor blocker (ARB)), environmental factors (diet, xenobiotics) and other systemic diseases of proven oxidative stress aetiology (e.g., diabetes, heart failure, thyroid and autoimmune diseases) may also disturb total antioxidant potential. The gene discussed is ACE; the disease is thyroid gland disorder.