Endocrine Abstracts

Introduction: Treatment of hypothyroidism with levothyroxine is effective and simple; however, international guidelines advise starting with low doses in case of severe hypothyroidism, cardiac illness and aged population. Interestingly, and in contradiction to this dogma, high doses of levothyroxine have been given to patients with myxedema coma without untoward effects. The difference between myxedema coma, which deserves an intensive treatment, and longstanding severe hypothyroidism is often a matter of precipitating event or time.

Material and methods: Retrospective analysis of clinical evolution of 70 patients (49 females) with ages between 21 and 92 years (mean: 52.8) with severe hypothyroidism (mean TSH levels of 104.1 mUI/L (± 34.6), ranging 52.63 mUI/L to 239.53 mUI/L) treated from 2004 to 2018 at our institution with intravenous levothyroxine at variable doses (most frequently 500 micrograms (divided in 400 and 100 micrograms the next day) with a mean dose of 433.3 micrograms and 2.1 (+0.5) days of treatment. Hormonal profile and cardiac safety were assessed daily with electrocardiogram studies. Data were analyzed with the Statistical Package for Social Science (SPSS), version 20.0.

Results: Free T4 became normal in 6.33 days, free T3 in 8.4 days and TSH in 33.5 days. No statistical differences after treatment were observed in blood pressure or electrocardiogram studies after analyzing heart rate, PR, QRS and QT intervals Analysis of data in patients aging more than 65 years or with a previous history of cardiac illness did not differ from the entire population. No serious adverse effects were observed (palpitations, angina pectoris, or other cardiac events) despite 17.14% of patients had some kind of previous heart disease. Up to 97.1% of patients described a sudden non-specific improvement of symptoms during admission,and no new admissions or visits to the emergency room were recorded for one month after treatment.

Conclusions: Intravenous intensive levothyroxine treatment in patients with severe hypothyroidism provides a fast and safe relief in clinical symptoms and biochemical alterations with no evidence of serious events. Moreover, our study also provides evidence that it is safe to treat patients older than 65 years with hypothyroidism with a full replacement dose of levothyroxine.