Why are internal medicine doctors hesitant to adjust thyroid medications, such as levothyroxine (Synthroid) or liothyronine (Cytomel), in hospitalized patients?

From the FDA Drug Label

Patients with underlying cardiovascular disease - Exercise caution when administering levothyroxine to patients with cardiovascular disorders and to the elderly in whom there is an increased risk of occult cardiac disease In these patients, levothyroxine therapy should be initiated at lower doses than those recommended in younger individuals or in patients without cardiac disease If cardiac symptoms develop or worsen, the levothyroxine dose should be reduced or withheld for one week and then cautiously restarted at a lower dose Overtreatment with levothyroxine sodium may have adverse cardiovascular effects such as an increase in heart rate, cardiac wall thickness, and cardiac contractility and may precipitate angina or arrhythmias

Internal medicine doctors may be hesitant to adjust thyroid medications, such as levothyroxine, in hospitalized patients due to the potential for adverse cardiovascular effects. This is particularly concerning in patients with underlying cardiovascular disease, as overtreatment with levothyroxine can precipitate angina or arrhythmias. Therefore, it is recommended to exercise caution when administering levothyroxine to these patients and to initiate therapy at lower doses than those recommended for younger individuals or patients without cardiac disease 1.

From the Research

Internal medicine doctors are hesitant to adjust thyroid medications like levothyroxine (Synthroid) or liothyronine (Cytomel) in hospitalized patients primarily because acute illness can temporarily alter thyroid function test results without reflecting true thyroid status. During hospitalization, patients often experience "sick euthyroid syndrome" or "non-thyroidal illness syndrome," where TSH and T3/T4 levels may be abnormal due to the stress response rather than actual thyroid dysfunction, as noted in a study published in the Pakistan journal of medical sciences 2. Levothyroxine has a long half-life of 7 days, meaning any dose changes take 5-6 weeks to reach steady state and show their full effect. Making adjustments based on tests during acute illness could lead to inappropriate dosing once the patient recovers. Additionally, many factors in the hospital setting can affect thyroid medication absorption, including NPO status, medication timing relative to food, and interactions with other drugs like antacids, calcium, or iron supplements. Some key points to consider include:

• The potential for patient requests to impact physician management of hypothyroidism, as reported in a study published in the Thyroid journal 3
• The importance of considering the individual patient's circumstances, such as age, sex, and special circumstances like pregnancy, when interpreting thyroid function tests, as highlighted in a recent review published in the Lancet 4
• The need for careful evaluation of thyroid function tests and clinical presentation to determine the best course of treatment, as illustrated in a case report published in the European journal of case reports in internal medicine 5 Unless the patient shows clear signs of severe hypothyroidism or thyrotoxicosis requiring immediate intervention, the standard approach is to continue the patient's home dose and schedule follow-up thyroid function testing 6-8 weeks after discharge when the patient has returned to their baseline health status. This approach is supported by the most recent and highest quality evidence, including a review published in the Lancet in 2024 4.