Managing Levothyroxine Malabsorption in Refractory Hypothyroidism: A Case Report.

Levothyroxine malabsorption is a rare but important cause of refractory hypothyroidism that necessitates alternative therapeutic approaches. We present the case of a 55-year-old woman with long-standing hypothyroidism who continued to experience persistent symptoms despite being on high-dose oral levothyroxine (1500 mcg daily). Laboratory investigations revealed an elevated thyroid-stimulating hormone (TSH) level of 14.160 mIU/L, along with positive anti-gliadin and anti-parietal cell antibodies. A supervised thyroxine (T4) absorption test confirmed true levothyroxine malabsorption. The patient was subsequently transitioned to a liquid levothyroxine formulation at a reduced dose of 600 mcg, which led to significant clinical improvement and normalization of thyroid function. Levothyroxine malabsorption can be attributed to underlying gastrointestinal conditions such as celiac disease and atrophic gastritis. The T4 malabsorption test is a valuable tool in distinguishing true malabsorption from non-adherence or pseudo-malabsorption. In cases of confirmed malabsorption, liquid or parenteral formulations may help improve absorption and lead to better clinical outcomes. This case highlights the importance of identifying thyroid hormone malabsorption in patients with refractory hypothyroidism to ensure optimal management and therapeutic success.