From the Guidelines
Subclinical hypothyroidism should be treated with levothyroxine in patients with TSH levels above 10 mIU/L or those with TSH between 4.5-10 mIU/L who have symptoms of hypothyroidism, are pregnant, or have other risk factors like positive thyroid antibodies or cardiovascular disease. The decision to treat subclinical hypothyroidism is based on the potential benefits of preventing progression to overt hypothyroidism, reducing cardiovascular risk, and improving quality of life by alleviating symptoms like fatigue, cold intolerance, and cognitive difficulties that may be present even in subclinical disease 1.
Key Considerations
- The standard treatment is levothyroxine (synthetic T4), typically starting at 25-50 mcg daily for older adults or those with heart disease, and 50-75 mcg daily for younger, otherwise healthy individuals.
- Dosage should be adjusted every 6-8 weeks based on TSH levels, with the goal of achieving a TSH within the reference range (typically 0.4-4.0 mIU/L) 1.
- 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.
- Regular monitoring is essential, with TSH checks every 6-12 months once stable.
Potential Harms
- Overdiagnosis and overtreatment are potential harms of screening for thyroid dysfunction, particularly in asymptomatic individuals with mildly elevated TSH levels 1.
- The harms of treatment of thyroid dysfunction have not been well-studied, but may include false-positive results, labeling, and overdiagnosis and overtreatment 1.
Evidence Summary
The evidence suggests that treatment of subclinical hypothyroidism can improve symptoms and quality of life, but the decision to treat should be individualized based on the presence of symptoms, risk factors, and TSH levels 1. The potential harms of overdiagnosis and overtreatment should also be considered, particularly in asymptomatic individuals with mildly elevated TSH levels 1.
From the FDA Drug Label
The FDA drug label does not answer the question.
From the Research
Definition and Diagnosis of Subclinical Hypothyroidism
- Subclinical hypothyroidism is a biochemical condition defined by elevated serum thyroid-stimulating hormone (TSH) levels in the setting of normal levels of the peripheral thyroid hormones, thyroxine and triiodothyronine 2.
- The diagnosis of subclinical hypothyroidism should be confirmed by repeat thyroid function tests ideally obtained at least 2 months later, as 62% of elevated TSH levels may revert to normal spontaneously 3.
Treatment of Subclinical Hypothyroidism
- Generally, treatment is not necessary unless the TSH exceeds 7.0-10 mIU/L 3.
- Levothyroxine, in a dosage that maintains serum TSH levels within the normal range, is the preferred therapy in patients with definite and persistent TSH elevation 4.
- Treatment with levothyroxine may only provide benefit in certain subgroups, such as patients who are younger or at higher risk of cardiovascular disease 2.
- Current research supports that levothyroxine should be initiated in patients with a TSH >10 mIU/L 5.
Effects of Treatment on Symptoms and Cardiovascular Disease
- Symptoms related to vitality, weight, and quality of life in subclinical disease often persist with levothyroxine treatment, and other causes should be explored 5.
- Patients with cardiovascular-risk factors may benefit from treatment, especially younger patients 5.
- Caution is necessary when treating elderly subjects with levothyroxine, as treatment may be harmful in elderly patients with subclinical hypothyroidism 3.
- While cardiovascular events may be reduced in patients under age 65 with subclinical hypothyroidism who are treated with levothyroxine, the use of levothyroxine in subclinical hypothyroidism to reduce cardiovascular disease risk is not clearly beneficial 2.
Alternative Treatments
- For patients who remain symptomatic on levothyroxine therapy, clinical guidelines recommend, on a trial basis, therapy with levothyroxine and liothyronine (LT3) 6.
- Desiccated thyroid extract (DTE) is a form of combination therapy in which the LT4/LT3 ratio is ∼4:1, but the consistency of T4 and T3 contents is monitored by the manufacturers only 6.