From the Guidelines
A TSH level of 150 mIU/L can be treated orally with levothyroxine (T4) as the principal treatment for hypothyroidism, according to the U.S. Preventive Services Task Force recommendation statement 1. The typical starting dose for adults with severe hypothyroidism is 50-100 mcg daily, with gradual increases every 6-8 weeks based on TSH monitoring. For elderly patients or those with cardiovascular disease, a lower starting dose of 12.5-25 mcg daily is recommended to avoid cardiac complications. Full replacement doses typically range from 1.6-1.8 mcg/kg of body weight daily. The medication should be taken on an empty stomach, 30-60 minutes before breakfast, and separated from other medications that may interfere with absorption (like calcium, iron supplements, or antacids) by at least 4 hours. Some key considerations in treating hypothyroidism include:
- Monitoring TSH levels 6-8 weeks after starting treatment or changing doses, with a goal of bringing TSH into the normal range (typically 0.4-4.0 mIU/L) 1.
- Being aware that while oral levothyroxine is effective for treating hypothyroidism, the evidence for its benefit in asymptomatic persons with abnormal TSH levels is lacking 1.
- Understanding that the natural history of subclinical hypothyroidism and the small but definite risk of progression to overt hypothyroidism should be considered when deciding on treatment 1. Oral levothyroxine is effective because it gets converted to the active hormone T3 in the body's tissues, normalizing metabolism and reversing hypothyroid symptoms.
From the FDA Drug Label
The FDA drug label does not answer the question.
From the Research
Treatment of High TSH Levels
- A TSH level of 150 is considered high and requires treatment to normalize the level and alleviate symptoms of hypothyroidism.
- According to the study by 2, normalizing serum TSH in hypothyroid patients can reduce the risk of death, and the implementation of a policy of normalizing serum TSH is estimated to reduce the risk of death of 28.3 million people in the USA and Europe alone.
Oral Treatment Options
- Levothyroxine (LT4) is the standard treatment for hypothyroidism, and it can be taken orally to normalize TSH levels 3.
- Some patients may not respond to LT4 alone and may require combination therapy with liothyronine (LT3) 4.
- The study by 5 suggests that estimating residual thyroid function (RTF) can help optimize combination LT4 + LT3 therapy, and provides an algorithm for estimating RTF and optimizing patient dosing.
- A recent feasibility trial by 6 found that LT4/LT3 combination therapy may prevent changes in weight and cholesterol associated with LT4 replacement alone in post-surgical hypothyroidism.
Considerations for Treatment
- The decision to start treatment with LT3 should be a shared decision between patient and clinician, and individual clinicians should not feel obliged to start LT3 or continue LT3 medication if they judge it not to be in the patient's best interest 4.
- The study by 3 suggests that 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 for combination therapy.
- The study by 5 provides recommended once-daily starting doses for combination LT4 + LT3 therapy based on estimated RTF.