A 50-year-old woman who is known case of hypothyroidism and is taking treatment for the same, was diagnosed with endometrial fibroids and staed on iron recently. She repoed excessive fatigue & constipation in her follow up visit. Her BP & cholesterol levels have been stable. A TSH is checked, and it is found to be elevated. What is the most likely cause of her elevated TSH?
High-Yield Explanation
Ferrous sulfate interferes with absorption of levothyroxine thus leading to low levels of thyroid hormone & elevated levels of TSH In patients with normal body weight taking >200 mg of levothyroxine per day, an elevated TSH strongly suggests noncompliance Malabsorption syndrome (celiac disease)- leads to elevated TSH & increased requirement of thyroxine