Gut Check: Resolving Refractory Hypothyroidism through H. Pylori Eradication

Background/Objective Refractory hypothyroidism is often attributed to levothyroxine nonadherence, improper administration, or malabsorption, with Helicobacter pylori gastritis representing an underrecognized but reversible cause. The objective of this report is to describe a patient with coexisting autoimmune disease whose refractory hypothyroidism resolved after Helicobacter pylori eradication, highlighting the importance of considering this treatable etiology when other causes of malabsorption have been excluded. Case report A 37-year-old man with Hashimoto's thyroiditis, trisomy 21, and celiac disease presented for a second opinion regarding persistent hypothyroidism despite escalating levothyroxine doses and associated weight loss. He was taking levothyroxine 225 mcg daily despite weighing 46 kg, with confirmed medication adherence, gluten-free diet compliance, and proper dosing separation from food and supplements. Thyroid-stimulating hormone was 112 uIU/mL (0.45-5.33 uIU/mL) with free thyroxine 0.38 ng/dL (0.80-1.80 ng/dL). Upper endoscopy showed atrophic mucosa with biopsy-proven gastritis and organisms compatible with Helicobacter pylori. He completed triple therapy with clarithromycin, lansoprazole, and metronidazole, with eradication confirmed by negative stool antigen testing. Over subsequent months, thyroid-stimulating hormone became persistently low, requiring serial levothyroxine dose reductions, and he achieved sustained euthyroidism on levothyroxine 75 mcg daily. Discussion This case highlights Helicobacter pylori gastritis as a reversible cause of levothyroxine malabsorption. The dramatic biochemical response after eradication underscores the need for close endocrine monitoring to prevent iatrogenic thyrotoxicosis as absorption normalizes. Conclusion Clinicians should suspect Helicobacter pylori and other gastric disorders in patients with markedly supraphysiologic or weight-discordant levothyroxine requirements, especially in populations with autoimmune comorbidities.