Is Parenteral Levothyroxine Therapy Safe in Intractable Hypothyroidism?

Alternative routes of levothyroxine administration for hypothyroidism

PURPOSE OF REVIEW

The aim of the article is to present the basics of oral levothyroxine (LT4) absorption, reasons why patients may have persistently elevated serum thyroid stimulation hormone (TSH) levels, and alternative strategies for LT4 dosing.

RECENT FINDINGS

Although oral LT4 tablets are most commonly used for thyroid hormone replacement in patients with hypothyroidism, case studies report that liquid oral LT4, intravenous, intramuscular, and rectal administration of LT4 can successfully treat refractory hypothyroidism.

SUMMARY

Hypothyroidism is one of the most common endocrine disorders encountered by primary care physicians and endocrinologists. LT4 is one of the most widely prescribed medications in the world and it is the standard of care treatment for hypothyroidism. Generally, hypothyroid patients will be treated with LT4 tablets to be taken orally, and monitoring will occur with routine serum thyroid tests, including TSH concentrations. However, many patients fail to maintain serum TSH levels in the target range while managed on oral LT4 tablets. A subset of these patients would be considered to have poorly controlled hypothyroidism, sometimes termed refractory hypothyroidism. For these patients, optimization of ingestion routines and alternative formulations and routes of administration of LT4 can be considered, including oral liquid, intravenous, intramuscular, and even rectal formulations.

Management of endocrine conditions at the end of life

An important facet to end-of-life care is deprescribing. This can be challenging when reviewing life-sustaining endocrine medications but, unlike for diabetes, there is no national guidance to support patients and clinicians faced with care planning. This article reviews the limited current evidence to highlight areas for further discussion and research with the aim of moving towards consensus opinion. Discontinuation of certain endocrine medications, including corticosteroids, desmopressin and levothyroxine, is likely to precipitate an 'endocrine-driven mechanism of death', while it may be reasonable to discontinue other endocrine medications without the risk of hastening death or causing unnecessary symptoms. However, the over-arching theme should be that early discussion with patients regarding conversion or discontinuation of endocrine medications or monitoring is central to care planning.

Treatment with Intramuscular Levothyroxine in Refractory Hypothyroidism

INTRODUCTION

Orally and daily levothyroxine (LT4) is the treatment of choice for hypothyroidism. In the majority of cases, the lack of effectiveness by this way may be due to poor adherence; however, gastrointestinal malabsorption may explain more cases of thyroxine refractoriness than previously reputed, due to the number of occult forms of these disorders.

CASE PRESENTATION

A 55-year-old white man with a diagnosis of low risk of recurrence of follicular variant of papillary thyroid carcinoma was treated with total thyroidectomy, 30 mCi iodine 131, and oral LT4. A year before he presented a gastric adenocarcinoma that required a partial gastrectomy. He evolved with multiple episodes of intestinal subocclusion that had to be treated with enterectomy in the first instance, then digestive rest and total parenteral nutrition. In spite of having made increases in oral LT4 dose (3 µg/kg), the patient persisted with a thyroid-stimulating hormone level >100 mIU/L. For this reason, we decided to administer intramuscular LT4.

CONCLUSION

Since there are no guidelines or consensus of intramuscular LT4 use, our experience and how we decided the dose and way of administration are presented in this article to contribute to future cases.

Intramuscular levothyroxine: a solution to a mental health related thyroid crisis

A 53-year-old woman was admitted with thyroid storm and severe behavioural problems. She had longstanding bipolar affective disorder. She was psychotic and obstructed in-patient medical management for thyroid storm. She required one-to-one psychiatric nursing and was placed under section 3 of the Mental Health Act meaning she could be detained in hospital for psychiatric treatment for up to 6 months. She underwent a total thyroidectomy. Due to her paranoid mental state, she refused treatment and the administration of thyroid hormone replacement was difficult. Postoperatively, intramuscular levothyroxine was used effectively to stabilise her thyroid function. There are no consensus guidelines on the use of parenteral levothyroxine and intramuscular levothyroxine is rarely used. This case uniquely illustrates its utility with bi-weekly blood tests showing a fast and stable response to intramuscular hormone replacement.