Refractory hypothyroidism: True malabsorption or pseudo-malabsorption?

Abstract

Hypothyroidism is one of the most common endocrinopathies. Its treatment consists of hormonal supplementation with levothyroxine. Despite the simplicity and accessibility of this treatment, cases of refractory hypothyroidism have been reported despite high doses. Our case is a new observation exposing this problem while discussing the modalities of its management. Patient aged 34, followed for 6 months for hypothyroidism post total thyroidectomy. She was taking 300 μg/day of levothyroxine. The patient reported compliance with her treatment. She did not report taking any other medications. Clinical examination revealed that the patient was profoundly hypothyroid. Biological tests showed TSH > 100 μUI/mL (0.35-4.94), FT4 less than 0.40 (0.7-1.48) and FT3< 1.07 pg/mL (1.71-3.71). After eliminating all obvious causes, an oral thyroid hormone absorption test was performed in hospital, with FT4 measurements at H0, H2, H4 and H6 after levothyroxine intake. The results showed increasing FT4 elevation, eliminating the diagnosis of malabsorption and testifying to our patient's poor compliance with treatment. We report on a case that highlights the value of the thyroid hormone absorption test, which can help distinguish between true malabsorption and pseudo-malabsorption, in which case re- education on proper compliance and possible psychological follow-up are required.