From the Guidelines
Treatment for subclinical hypothyroidism should be considered when TSH levels exceed 10 mIU/L, regardless of symptoms, or when TSH is between 4.5-10 mIU/L with symptoms of hypothyroidism or certain risk factors, as evidenced by recent guidelines 1, 2.
Key Considerations
- The decision to treat subclinical hypothyroidism should be based on individual patient factors, including symptoms, risk factors, and quality of life considerations.
- Levothyroxine is the standard treatment, typically starting at 25-50 mcg daily for most adults, with lower doses (12.5-25 mcg) for elderly patients or those with cardiac disease.
- The goal of treatment is to normalize TSH levels to 0.5-4.5 mIU/L, with dose adjustments made every 6-8 weeks based on TSH measurements.
Patient-Specific Factors
- Treatment should be considered for pregnant women or those planning pregnancy (target TSH <2.5 mIU/L), patients with positive thyroid antibodies, goiter, dyslipidemia, or cardiovascular risk factors.
- Younger patients (<65 years) with symptoms are more likely to benefit from treatment than asymptomatic elderly patients.
- Regular monitoring is essential, with TSH checks 6-8 weeks after starting therapy or changing doses, then annually once stable, as recommended by the U.S. Preventive Services Task Force 1.
Evidence-Based Recommendations
- The evidence does not show important benefits of treatment of subclinical thyroid dysfunction on blood pressure, BMI, lipid levels, cognitive function, or quality of life, but treatment may have long-term benefits on final health outcomes, such as reduced bone fractures and cardiovascular- and cancer-related morbidity and mortality 2.
- Long-term observational studies are needed to better understand the natural history of untreated, asymptomatic thyroid dysfunction and outcomes in persons with common but nonspecific symptoms.
From the Research
Treatment of Subclinical Hypothyroidism
- Subclinical hypothyroidism is a biochemical condition defined by elevated serum thyroid-stimulating hormone (TSH) levels with normal levels of peripheral thyroid hormones, thyroxine and triiodothyronine 3.
- The diagnosis of subclinical hypothyroidism should be confirmed by repeat thyroid function tests, as 62% of elevated TSH levels may revert to normal spontaneously 4.
- Generally, treatment is not necessary unless the TSH exceeds 7.0-10 mIU/L 4, with most studies suggesting treatment should be initiated in patients with a TSH >10 mIU/L 5, 6, 7.
Indications for Treatment
- Treatment may be indicated for patients with subclinical hypothyroidism and serum TSH levels of 10 mU/L or higher 6, 7.
- Young and middle-aged individuals with subclinical hypothyroidism and symptoms consistent with mild hypothyroidism may also benefit from treatment 7.
- Patients with cardiovascular risk factors, especially younger patients, may benefit from levothyroxine therapy 5, 3.
- Caution is necessary when treating elderly subjects with levothyroxine, as it may be harmful in this population 4, 7.
Considerations for Treatment
- 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 4.
- Levothyroxine therapy may be associated with iatrogenic thyrotoxicosis, especially in elderly patients 7.
- The introduction of substitution therapy in patients with TSH <10 mU/L should be considered in the presence of general symptoms, anti-thyroid antibodies, increased lipids, and other risk factors 6.