Endocrine Abstracts

Several preparations of thyroxine are available nowadays but is a great challenge for every clinician when the oral and intramuscular administration is failing and has to consider long term intravenous administration. This is a 42 years old lady who had a total thyroidectomy for Graves thyrotoxicosis. She commenced on multiple oral preparations of thyroxine and liothyroxine with no biochemical response. This is not a case of pseudomalabsorption as oral absorption studies of high dose of Thyroxine have shown a flat plasma T₄ level. Further gastroenterological investigations failed to reveal any cause of malabsorption. Alternative option was the intramuscular thyroxine. She required twice weekly intramuscular thyroxine to maintain her euthyroid status but in two occasions she has been admitted with severe hypothyroidism complicated by bradycardia and polymorphic ventricular tachycardia. The cardiological complications, the distressing symptoms and the irregular/erratic absorption made this preparation not suitable, as well. Marked increased sensitivity to the effect of catecholamines has been identified as evidenced by the effects of isoprenaline during the Electrophysiology study. The last option in order to achieve effective and controlled administration was the intravenous thyroxine. She is currently on intravenous Levothyroxine in order to maintain a TSH between 10 and 20 mU/l. A subclavian port-a-cath system is currently required which unfortunately in several times has been infected. Being profoundly hypothyroid for some time has made her sympathetic system very sensitive to changes in the level of serum T₃. The above TSH range is important in order to prevent significant bradycardia and ventricular tachycardia but also to maintain a reasonable satisfactory thyroid status. This is a rare case of hypothyroidism requiring long term intravenous thyroxine with endocrinological and cardiological interest. There is no similar case previously reported in the literature.