Endocrine Abstracts

Pseudomalabsorption of Levothyroxine Hypothyroidism due to non-compliance with levothyroxine therapy (pseudomalabsorption) is rare. The diagnosis is considered in patients with persistent refractory hypothyroidism despite treatment high doses of levothyroxine. Intestinal malabsorption, drug and dietary interference with levothyroxine absorption and nephrotic syndrome should be excluded. The diagnosis of pseudomalabsorption can be demonstrated by using levothyroxine absorption protocol, showing a rapid decrease in thyroid-stimulating hormone and increase in thyroxine. There are however few data on the sensitivity and specificity of the test in large cohorts of hypothyroid patients. Treatment of pseudomalabsorption is controversial, with reports using parenteral, intramuscular or single weekly oral dosing of levothyroxine.

Case: We report 46 years old women who presented with persistent clinical and biochemical signs of hypothyroidism after thyroidectomy despite treatment with levothyroxine doses in excess of weight based calculations. Digestive, liver and kidney diseases were excluded. Levothyroxine absorption test was performed and percent absorbtion was calculated, which was nonconlusive 55% (normal >≥60 %). For further diagnosis and management patient had been hospitalized in our clinic for 5 days. Daily PO Levothyroxine administration was supervised by nurse resulting in improvement of TSH and serum thyroxine compared to pre-admission and admission day results confirming pseudomalabsorption. Patient and the care givers were appropriately instructed. Patient was referred for psychiatric evaluation.

Conclusions: Non-compliance with medical therapy should be considered in patients with treatment refractory hypothyroidism. Supervised PO levothyroxine administration with pre and post admission TSH and thyroxine measurement could be considered as the tool to exclude or confirm pseudomalabsobtion. Apart from the routine diagnostic approach, there is also a need for psychiatric evaluation and care.