Mercury (Hg), particularly in its organic methylmercury form, is a potent toxicant that disrupts thyroid function through a specific molecular attack. The activation and regulation of thyroid hormones rely heavily on a family of enzymes called deiodinases (D1, D2, D3). These enzymes convert the less active thyroxine (T4) into the potent triiodothyronine (T3) or break down hormones when necessary. Crucially, deiodinases are selenoenzymes, meaning they contain the rare amino acid selenocysteine at their active site. Mercury has an extremely high affinity for selenium and selenol (-SeH) groups. By binding irreversibly to the selenocysteine in deiodinases, mercury inactivates these enzymes. This disrupts the local conversion of T4 to T3 in tissues like the brain, leading to a functional hypothyroidism even if blood levels appear normal.

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Zambia

• ivwananji siwale – 29 pts

• Visual Pathway Lesions
• Positive and Negative Symptoms
• Hallucinations and Delusions
• Antipsychotic Medications
• Emergency: Environmental Emergencies