From the Guidelines
Subclinical hypothyroidism should be treated with levothyroxine if TSH levels are consistently above 10 mIU/L or if symptoms are present, as this approach has been shown to improve clinical outcomes in certain patient populations 1. For most patients with TSH between 4.5-10 mIU/L, a watch-and-wait approach is recommended, as the evidence for treatment in this range is less clear 1. If treatment is initiated:
- Start with levothyroxine 25-50 mcg daily, taken on an empty stomach
- Adjust dose every 6-8 weeks based on TSH levels
- Target TSH level: 0.5-2.5 mIU/L
- Monitor annually once stable Additional considerations:
- Pregnancy: Treat if TSH > 2.5 mIU/L in first trimester
- Elderly: Higher TSH threshold for treatment (>7-8 mIU/L)
- Check TPO antibodies to assess risk of progression to overt hypothyroidism It is essential to note that the decision to treat subclinical hypothyroidism should be individualized, taking into account the patient's symptoms, medical history, and laboratory results, as the current evidence does not support a one-size-fits-all approach 1. The goal of treatment is to prevent progression to overt hypothyroidism and potentially improve subtle symptoms like fatigue or mild cognitive impairment, while minimizing the risk of overtreatment and iatrogenic hyperthyroidism 1. In patients with subclinical hypothyroidism, careful monitoring of TSH levels and clinical symptoms is crucial to ensure that treatment is effective and safe, and to adjust the treatment plan as needed 1.
From the Research
Diagnosis of Subclinical Hypothyroidism (SCH)
- Subclinical hypothyroidism is defined as an elevated Thyroid-Stimulating Hormone (TSH) concentration in the presence of normal serum free thyroxine (T4) and triiodothyronine (T3) concentrations 2, 3, 4, 5
- 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 6
- The likelihood of progression to overt hypothyroidism increases with greater TSH elevations and detectable antithyroid antibodies 2, 4
Treatment of Subclinical Hypothyroidism (SCH)
- All patients with overt hypothyroidism and subclinical hypothyroidism with TSH >10 mIU/L should be treated 2
- There is consensus on the need to treat subclinical hypothyroidism of any magnitude in pregnant women and women who are contemplating pregnancy, to decrease the risk of pregnancy complications and impaired cognitive development of the offspring 2, 3
- Treatment should be considered in symptomatic patients, patients with infertility, and patients with goitre or positive anti-thyroid peroxidase (TPO) antibodies 2, 3
- Levothyroxine (LT4) monotherapy remains the current standard for management of primary, as well as central, hypothyroidism 2
- Treatment can be started with the full calculated dose for most young patients, but should be initiated at a low dose in elderly patients, patients with coronary artery disease and patients with long-standing severe hypothyroidism 2
- In primary hypothyroidism, treatment is monitored with serum TSH, with a target of 0.5-2.0 mIU/L 2
- 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
Special Considerations
- Limited evidence suggests that treatment of subclinical hypothyroidism in patients with serum TSH of up to 10 mIU/L should probably be avoided in those aged >85 years 2
- Other pituitary hormones should be evaluated in patients with central hypothyroidism, especially assessment of the hypothalamic-pituitary-adrenal axis, since hypocortisolism, if present, needs to be rectified prior to initiating thyroid hormone replacement 2
- Combined treatment with levothyroxine and liothyronine may be preferred in some hypothyroid patients who are dissatisfied with treatment, especially those with a polymorphism in type 2 deiodinase 6