When to treat subclinical hypothyroidism?

From the Guidelines

Treatment of subclinical hypothyroidism is generally recommended 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. This approach is based on expert opinion, as noted in the study by 1, which highlights the lack of clinical trial data supporting a specific treatment threshold to improve clinical outcomes. However, a TSH level greater than 10.0 mIU/L is considered the threshold for initiation of treatment due to the higher likelihood of progression to overt thyroid dysfunction.

Key Considerations for Treatment

• TSH levels: Treatment is considered when TSH levels exceed 10 mIU/L or are between 4.5-10 mIU/L with symptoms or risk factors.
• Symptoms: Presence of symptoms such as fatigue, mild depression, or cognitive issues may prompt treatment at lower TSH levels.
• Risk factors: Factors like pregnancy or planning pregnancy, presence of thyroid antibodies, goiter, dyslipidemia, or depression may also lead to treatment at lower TSH levels.

Treatment Approach

• Levothyroxine (T4) is the standard treatment, typically starting at 25-50 mcg daily for older adults or those with heart disease, and 50-75 mcg daily for younger patients.
• Dose adjustment: Every 6-8 weeks based on TSH levels, aiming for a target TSH of 0.5-3.5 mIU/L.
• Administration: Levothyroxine should be taken on an empty stomach, 30-60 minutes before breakfast or 3-4 hours after the last meal of the day, and separated from medications containing calcium, iron, or antacids by at least 4 hours.

Monitoring and Follow-Up

• Regular TSH tests every 6-12 months are necessary to ensure proper dosing and to monitor for potential progression to overt hypothyroidism, as discussed in the context of thyroid dysfunction screening by 1.

From the Research

Decision to Treat Subclinical Hypothyroidism

The decision to treat subclinical hypothyroidism should be made after careful consideration of the patient's age, the presence of symptoms, the presence of thyroid antibodies, and other risk factors such as cardiovascular disease 2.

Factors Influencing Treatment Decision

• Patient's age: Treatment may be beneficial for younger patients (<65 years) with subclinical hypothyroidism, especially those with TSH levels ≥10.0 mu/L, as it may reduce the risk of coronary heart disease 2, 3.
• Presence of symptoms: Only a small minority of patients with subclinical hypothyroidism have symptoms, and the evidence to support that levothyroxine ameliorates these symptoms is weak 2.
• Presence of thyroid antibodies: Patients with thyroid autoantibodies and higher TSH levels have a higher rate of progression to clinically overt hypothyroidism 2.
• Cardiovascular risk factors: Patients with cardiovascular-risk factors may benefit from treatment, especially younger patients 3.

TSH Levels and Treatment

• Treatment is generally not necessary unless the TSH exceeds 7.0-10 mIU/L 4.
• Levothyroxine therapy may be indicated for patients with subclinical hypothyroidism and serum TSH levels of 10 mU/L or higher 5, 3, 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 4.

Special Considerations

• Elderly patients: Treatment may be harmful in elderly patients with subclinical hypothyroidism, and caution is necessary when treating elderly subjects with levothyroxine 4, 3.
• Pregnancy and ovarian dysfunction: Introduction of substitution therapy may be considered in patients with TSH <10 mU/l in the case of pregnancy, ovarian dysfunction, and infertility 6.