Hello. Hypothyroidism, uv damage, ageing process lead to dull and patchy facial skin. You should use a gel based sunscreen with at least 30 spf everyday. Use a cream containing Kojic acid twice a day( in morning before sunscreen) . Drink plenty of water. Keep your thyroid under control. You can get chemical peeling done by your nearest dermatologist. It will remove dullness and will also give glow to your skin.