امرأة عمرها ٤٩ سنة مصابة بقصور الدرقية، تأخذ ليفوثيروكسين ١٠٠ ميكروغرام. بدأت مؤخراً حبوب كالسيوم وحديد مع الفطور، وتأخذ الليفوثيروكسين معها. صار TSH مرتفعاً بعد ما كان طبيعياً، وتشعر بالتعب. ما التفسير الأرجح؟

A 49-year-old woman with hypothyroidism on levothyroxine 100 mcg recently started calcium and iron tablets at breakfast, taking them with her levothyroxine. Her TSH is now high after being normal, and she feels tired. What is the most likely explanation?

1. Her thyroid has stopped entirely and needs surgery
2. The levothyroxine suddenly expired
3. Calcium and iron reduced levothyroxine absorption
4. She has developed hyperthyroidism

Answer: C) Calcium and iron reduced levothyroxine absorption. Calcium and iron bind levothyroxine and reduce absorption; separate them by 4 hours and recheck TSH after 6–8 weeks.