What is the treatment for hypothyroidism using Liothyronine (Triiodothyronine)?

From the Guidelines

Liothyronine (T3) is a thyroid hormone medication used to treat hypothyroidism, though it's not typically the first-line treatment. The standard initial treatment for hypothyroidism is levothyroxine (T4), which the body converts to T3 as needed. Liothyronine may be prescribed when patients don't respond adequately to levothyroxine alone. Typical dosing starts low at 5-12.5 mcg daily and may be gradually increased to 25-75 mcg daily, divided into multiple doses due to its shorter half-life. Some patients benefit from combination therapy with both levothyroxine and liothyronine. When starting liothyronine, patients should be monitored with thyroid function tests every 4-8 weeks until stable, then every 6-12 months. Side effects of excessive dosing include heart palpitations, anxiety, insomnia, and weight loss. Liothyronine works faster than levothyroxine because it's the active form of thyroid hormone that directly affects metabolism, energy production, and body temperature regulation without requiring conversion. Patients with heart conditions should use liothyronine cautiously as it has more immediate cardiac effects than levothyroxine 1.

Some key points to consider when treating hypothyroidism with liothyronine include:

• Starting with a low dose and gradually increasing as needed
• Monitoring thyroid function tests regularly
• Being aware of the potential for side effects, particularly in patients with heart conditions
• Considering combination therapy with levothyroxine for some patients
• Understanding the natural history of subclinical hypothyroidism and the potential for progression to overt hypothyroidism 1.

It's also important to note that the evidence for the use of liothyronine in treating hypothyroidism is limited, and more research is needed to fully understand its effects and potential benefits 1.

However, based on the available evidence, the most appropriate treatment approach for hypothyroidism using liothyronine is to start with a low dose and gradually increase as needed, while monitoring thyroid function tests regularly and being aware of the potential for side effects.

From the FDA Drug Label

The dosage of thyroid hormones is determined by the indication and must in every case be individualized according to patient response and laboratory findings. Mild Hypothyroidism Recommended starting dosage is 25 mcg daily. Daily dosage then may be increased by up to 25 mcg every 1 or 2 weeks. Usual maintenance dose is 25 to 75 mcg daily Myxedema Recommended starting dosage is 5 mcg daily This may be increased by 5 to 10 mcg daily every 1 or 2 weeks. When 25 mcg daily is reached, dosage may be increased by 5 to 25 mcg every 1 or 2 weeks until a satisfactory therapeutic response is attained. Usual maintenance dose is 50 to 100 mcg daily

The treatment for hypothyroidism using Liothyronine (Triiodothyronine) is:

• Mild hypothyroidism: starting dosage is 25 mcg daily, with increases of up to 25 mcg every 1 or 2 weeks, and a usual maintenance dose of 25 to 75 mcg daily.
• Myxedema: starting dosage is 5 mcg daily, with increases of 5 to 10 mcg daily every 1 or 2 weeks, and a usual maintenance dose of 50 to 100 mcg daily. 2

From the Research

Treatment Overview

The treatment for hypothyroidism using Liothyronine (Triiodothyronine) involves a combination therapy with levothyroxine (LT4) for patients who remain symptomatic on LT4 therapy alone 3, 4, 5.

Combination Therapy

• Reducing the LT4 dose by 25 mcg/day and adding 2.5-7.5 mcg liothyronine (LT3) once or twice a day is an appropriate starting point 3.
• The LT4/LT3 ratio is typically around 13:1-20:1, with the goal of achieving a physiological ratio of free triiodothyronine/free thyroxine (FT3/FT4) and non-suppression of TSH 5.
• Desiccated thyroid extract (DTE) is a form of combination therapy with an LT4/LT3 ratio of around 4:1, but its use is not formally regulated by the FDA 3.

Efficacy and Safety

• Clinical trials have shown that combination therapy with LT4+LT3 can restore euthyroidism and improve symptoms in some patients, but the evidence is not conclusive 3, 4, 6.
• The addition of liothyronine to LT4 therapy has been shown to have minimal or no effect on fatigue, quality of life, mood, pain, cognitive function, and body weight in some studies 6.
• However, other studies suggest that combination therapy may be beneficial for patients who remain symptomatic on LT4 therapy alone, particularly those with polymorphism of the deiodinase 2 (D2) genes 5.

Patient Selection

• Newly diagnosed hypothyroid patients should be treated with LT4, and a trial of combination therapy with LT4+LT3 can be considered for those who have not benefited from LT4 alone 3, 4.
• The use of liothyronine should be individualized, and patients should be monitored closely for adverse effects and changes in thyroid function tests 3, 5.