Endocrine Abstracts

Introduction: Primary hypothyroidism is a common condition. Its treatment is simple and consists of daily levothyroxine intake. Cases with refractory hypothyroidism despite high doses of levothyroxine were reported. Herein, we report the case of a patient with refractory hypothyroidism secondary to gastrointestinal malabsorption that was improved by L-thyroxine liquid oral substitution.

Observation: A 49-year-old woman was admitted for refractory hypothyroidism. Her past medical history included Graves ‘disease treated with radioiodine therapy, asthma, and vitamin d deficiency. The patient was treated with levothyroxine 200 µg/day (2.63 μg/kg/day) with good compliance and regular intake. She presented with persistent symptoms of hypothyroidism and a TSH level of 72 mIU/l (nr: 0.35-4.95). A levothyroxine absorption test was performed by oral administration of 300 µg of levothyroxine (3 solid tablets of 100 µg each). The LT4 absorption rate was 25%, consistent with the diagnosis of malabsorption. A second absorption test was carried out by a concomitant oral administration of 300 µg of levothyroxine and 1 g of vitamin C. The LT4 absorption rate was 3 %. Sublingual administration of levothyroxine was not associated with the increase of FT4. Etiological investigations showed negative celiac disease serology and Helicobacter pylori (HP) gastritis. HP infection was treated but symptoms of hypothyroidism and elevated TSH persisted. The levothyroxine dose was progressively adjusted from 200 µg to 400 µg once a day. Biological tests showed a TSH level of 92.4 mIU/l and a FT4 level lower than 0.42 ng/dl (nr: 0.7-1.5). The patient was put on L-thyroxine in liquid form at a dose of 80 drops per day. Two weeks later, she presented with clinical improvement with a normal FT4 level at 1.14 ng/dl.

Conclusion: Refractory hypothyroidism has a significant impact on patients. It can be caused by several conditions such as poor compliance with levothyroxine therapy, drug interferences, and malabsorption syndrome. Liquid formulations tend to have a better effect on patients with gastritis or those receiving proton pump inhibitors. This is thought to be due to increased dissolution and absorption.