Introduction: Hypothyroidism is usually easily treated with levothyroxine tablets. Patients who show poor response to oral therapy are usually found to have inadequate absorption of levothyroxine, or non-compliance. We report a case where intramuscular thyroxine was used successfully in treating a case of resistant hypothyroidism due to possible malabsorption. Case report: A 47 year old lady with primary hypothyroidism, diagnosed aged 34 years, was referred to the endocrine clinic as she remained profoundly hypothyroid despite treatment with escalating doses of levothyroxine. She also had recurrent iron deficiency anaemia resistant to oral iron therapy, for which no cause was found. Other diagnoses included vitamin B12 deficiency, hypertension, stable CKD stage 3 and epilepsy. Clinically she was severely hypothyroid with mental slowness, thickened skin and hair and eyebrow loss. Despite ensuring compliance with oral levothyroxine (up to 1000 mcg a day) and avoiding drug induced malabsorption of levothyroxine, she became progressively more hypothyroid (TSH = 82.4 mU/L [reference range 0.26.0 mU/L], Free T4=2.1 pmol/L [ reference range 1020 pm/L]), suggesting the possibility of malabsorption of levothyroxine. Concomitant deficiency of iron, vitamin B12 and folic acid was found, lending credibility to the diagnosis. The cause for the malabsorption was not found. She was tried sequentially on levothyroxine syrup and a combination of levothyroxine (500 mcg) and leiothyronine (20 mcg), both of which failed to achieve euthyroidism. She was subsequently commenced on imported weekly intramuscular injections of levothyroxine 500 mcg. There has been a marked response biochemically (TSH= 7.8 mU/L, Free T4 = 12.8 pmol/L) after a years therapy so far. As expected, there has been a dramatic improvement in the patients physical and mental health. Discussion: This case suggests that intramuscular thyroxine can be used with success in the treatment of refractory hypothyroidism due to malabsorption of levothyroxine.
Declaration of interest: There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.
Funding: No specific grant from any funding agency in the public, commercial or not-for-profit sector.