Isolated thyroxine malabsorption treated with intramuscular thyroxine injections

An 18-year-old girl with multiple autoimmune endocrinopathies was referred to the endocrinology clinic for management of hypothyroidism. She required increasing doses of thyroxine but remained hypothyroid. Daily and weekly supervised thyroxine administration strategies were unsuccessful. She was extensively investigated for malabsorption; however, all the results were normal. She was subsequently commenced on weekly intramuscular thyroxine injections and became biochemically and clinically euthyroid. Subsequent elective hospital admission and administration of thyroxine via nasogastric tube resulted in recurrence of her hypothyroidism. This case demonstrates apparent isolated true levothyroxine malabsorption existing in isolation and suggests that intramuscular thyroxine injections may be a useful therapeutic modality in these patients.