At what Thyroid-Stimulating Hormone (TSH) level do you treat hypothyroidism?

From the Guidelines

Treatment for hypothyroidism is typically initiated when the thyroid stimulating hormone (TSH) level exceeds 10 mIU/L, regardless of symptoms. For TSH levels between 4.5-10 mIU/L (subclinical hypothyroidism), treatment decisions depend on individual factors such as symptoms, age, and the presence of thyroid antibodies or other health conditions 1. The standard treatment is levothyroxine (T4), starting at 1.6 mcg/kg/day for most adults, though lower doses (25-50 mcg/day) are recommended for elderly patients or those with heart disease.

Key Considerations

• Medication should be taken on an empty stomach, 30-60 minutes before breakfast or 3-4 hours after the last meal of the day, avoiding calcium, iron supplements, and certain foods that can interfere with absorption.
• TSH levels should be checked 6-8 weeks after starting treatment, with dose adjustments made to achieve a TSH level within the normal range (typically 0.4-4.5 mIU/L) 1.
• Treatment is necessary because hypothyroidism can lead to fatigue, weight gain, cold intolerance, and more serious complications like cardiovascular disease if left untreated.
• The decision of whether and when to begin therapy in patients with TSH levels between 4.5 and 10.0 mIU/L is more controversial, and the USPSTF recommends against routine screening for thyroid dysfunction in non-pregnant adults 1.

Monitoring and Adjustment

• Regular monitoring of TSH levels is crucial to adjust the dose of levothyroxine and prevent over- or under-treatment.
• Patients with subclinical hypothyroidism should be monitored annually for changes in TSH levels and symptoms.
• The goal of treatment is to achieve a TSH level within the normal range, which can help prevent long-term complications and improve quality of life 1.

From the FDA Drug Label

The general aim of therapy is to normalize the serum TSH level TSH may not normalize in some patients due to in utero hypothyroidism causing a resetting of pituitary-thyroid feedback. Failure of the serum T4 to increase into the upper half of the normal range within 2 weeks of initiation of levothyroxine sodium therapy and/or of the serum TSH to decrease below 20 IU per litre within 4 weeks may indicate the patient is not receiving adequate therapy In adult patients with primary hypothyroidism, monitor serum TSH levels after an interval of 6 to 8 weeks after any change in dosage. In patients on a stable and appropriate replacement dosage, evaluate clinical and biochemical response every 6 to 12 months and whenever there is a change in the patient’s clinical status New onset hypothyroidism (TSH ≥10 IU per liter) New onset hypothyroidism (TSH < 10 IU per liter)

Treatment of Hypothyroidism:

• The treatment aim is to normalize the serum TSH level.
• TSH levels should be monitored after an interval of 6 to 8 weeks after any change in dosage in adult patients with primary hypothyroidism.
• For new onset hypothyroidism, treatment is considered when TSH ≥10 IU per liter or TSH < 10 IU per liter, with different starting dosages.
• However, the exact TSH level at which to treat hypothyroidism is not explicitly stated, but rather to normalize the serum TSH level 2.

From the Research

Treatment of Hypothyroidism

• The treatment of hypothyroidism is based on clinical signs and symptoms, as well as measurement of thyroid-stimulating hormone (TSH) concentration 3, 4.
• Levothyroxine therapy is generally recommended for patients with overt hypothyroidism and a blood TSH concentration above 10 mIU/L 3, 4, 5.
• For subclinical hypothyroidism, treatment is usually recommended when the TSH level is above 10 mIU/L 3, 4, 6, 5.
• However, some studies suggest that treatment may not be necessary unless the TSH exceeds 7.0-10 mIU/L 6.
• TSH goals are age-dependent, with a 97.5 percentile (upper limit of normal) of 3.6 mIU/L for patients under age 40, and 7.5 mIU/L for patients over age 80 6.

Initiating Treatment

• Initiation of levothyroxine therapy depends on the level of TSH elevation, as well as other factors such as patient age, presence of pregnancy, or comorbidities 4.
• In young adults, levothyroxine is usually started at a dose of about 1.5 microg/kg per day, taken on an empty stomach 3.
• Elderly patients and those with coronary artery disease should start at a lower dose: 12.5 to 50 microg per day 3.

Monitoring Treatment

• Treatment monitoring is based mainly on blood TSH assay, and dose adjustment should only be considered after 6 to 12 weeks, given the long half-life of levothyroxine 3.
• Certain drugs, such as iron and calcium, reduce the gastrointestinal absorption of levothyroxine, and enzyme inducers reduce its efficacy 3.