Endocrine Abstracts

Background: Refractory hypothyroidism poses a clinical dilemma, with great difficulty to treat. Novel cases have targeted intramuscular (IM) levothyroxine (LT4) as a potential treatment for cases resistant to oral LT4. We discuss a patient who became intolerant of IM LT4 after 18 years of treatment, thus SC LT4 was initiated as alternative management.

Case Presentation: 35-year-old female with diagnosed Schmidt’s Syndrome and refractory hypothyroidism, was developing worsening side effects associated with IM LT4. She was initially diagnosed with hypothyroidism at 13-years-old, and remained hypothyroid despite escalating doses of oral LT4. Patient compliance was ensured, and common causes of resistant hypothyroidism excluded. Nasogastric investigation confirmed thyroxine malabsorption. She finally achieved euthyroid status at age of 18 with titrating regime of fortnightly IM LT4. This was maintained for 18 years. Unfortunately, scar tissue developed around injection sites, resulting in increased pain and difficulty of continued IM administration. An alternative management was thus sought. SC LT4 injections were trialled with success, and she has remained euthyroid on SC LT4 1200 micrograms every 12 days, for the last six years with minimal side effects.

Discussion: First-line treatment for hypothyroidism is oral LT4. Most patients require 1.6-1.8 microgram/kg dose to maintain euthyroid state. However, many cases in the literature note resistance to oral treatment ie. ‘refractory hypothyroidism’. The most reported treatment for refractory hypothyroidism is IM LT4, however IV LT4 is also recognised. Very few cases note the success of subcutaneous thyroxine to treat refractory hypothyroidism, and only one discusses its efficacy and safety over multiple (two) years. Our case highlights the benefit of SC LT4 injections over longer duration, which include ease of self-administration, safety, efficacy and reduced pain after chronic intramuscular injection use.

Conclusion: We wish to highlight SC LT4 as a safe, effective and alternative chronic treatment for refractory hypothyroidism.