Article Figures & Data
Figures
- Figure 1
Flow chart for clinical decision-making in subclinical hypothyroidism.
aRisk factors: TPOAb-positive, goiter, atherosclerotic cardiovascular disease, heart failure, or associated risk factors for these diseases.
bOral levothyroxine daily is the treatment of choice. For patients with cardiac disease, 1.5 μg/kg/day should be used. For elderly patients with cardiac disease, a dose of 25–50 μg/day is recommended. Increase dose by 12.5 to 25 μg/day every 2 to 3 weeks. Target TSH range is 0.4 to 2.5 mIU/L.
Tables
Test Advantages Disadvantages Preferred use Thyrotropin (thyroid-stimulating hormone, TSH)7 Sensitive to changes in thyroid hormone levels
Useful in diagnosing primary and secondary hypothyroidismCan be influenced by nonthyroid factors (eg, illness, medications) Primary test for diagnosing hypothyroidism and monitoring thyroid hormone replacement therapy Free thyroxine (T4)2,8 More accurate reflection of thyroid hormone levels than total T4, less influenced by changes in binding proteins Can be affected by protein-binding changes, especially in certain conditions (eg, pregnancy, liver disease) Essential for assessing thyroid hormone status, especially in conditions affecting thyroid-binding proteins Free triiodothyronine (T3)7,9 More accurate reflection of thyroid hormone activity than total T3, less influenced by changes in binding proteins Lower concentration, weaker protein binding, less precise measurement
Often normal in early and mild hypothyroidism due to mostly peripheral conversion, especially in early hypothyroidismConsider in specific clinical scenarios, such as suspected nonthyroid illness syndrome or hyperthyroidism Thyroglobulin Elevated levels may indicate residual or recurrent thyroid cancer Can be affected by thyroid inflammation and other factors Used in the management of patients with thyroid cancer Thyroid peroxidase antibodies Positive test suggests autoimmune thyroiditis; often associated with Hashimoto thyroiditis Not specific—can be positive in other autoimmune conditions Used in the diagnosis and management of autoimmune thyroid diseases Thyroid-stimulating hormone range (mIU/L) Free T4 range (ng/dL) Grade 1 4.0–10.0 Normal (0.9–1.7) Grade 2 > 10.0 Normal (0.9–1.7) Based on information from references 2 and 10.
Factor Explanation Time of day TSH levels naturally fluctuate throughout the day, peaking in the early morning hours Season of year TSH levels may be slightly higher in winter than in summer, potentially due to changes in sunlight exposure or other environmental factors Stress Can temporarily suppress TSH production Illness Infections or autoimmune diseases can disrupt the hypothalamic-pituitary-thyroid axis, leading to changes in TSH levels, depending on the severity or duration of the illness Medications Some medications, particularly those used to treat thyroid disorders or other conditions, can influence TSH levels Interindividual variation There can be significant individual differences in TSH patterns, even among healthy individuals; genetic factors and personal characteristics may play a role Age TSH levels tend to increase with age, particularly in older adults Sex Some studies suggest that there may be sex-specific differences in TSH regulation, so that women tend to have higher TSH levels than men14 Autoimmunity Autoimmune thyroid diseases such as Hashimoto thyroiditis can lead to elevated TSH levels, particularly in the early stages of the disease Based on information from references 14–21.
Organization Mild subclinical hypothyroidism (TSH 4.0–10.0 mIU/L) Severe subclinical hypothyroidism (TSH > 10.0 mIU/L) Key comments US Preventive Services Task Force (2015)1 Does not recommend routine screening or treatment Recommends treatment Insufficient evidence of benefit of treatment in patients without symptoms European Thyroid Association (2013)10 Watchful waiting, unless symptomatic
Consider treatment in younger individuals with persistent symptomsRecommends treatment Emphasizes a cautious approach, especially in older adults American Association of Clinical Endocrinology and American Thyroid Association (2012)2 Does not recommend routine screening or treatment in patients without symptoms
Consider treatment in select cases based on individual factorsRecommends treatment Highlights individualizing treatment decisions and considering factors such as age, comorbidities, and symptom burden American Thyroid Association (2014 update)3 Similar to 2012 guidelines, emphasizing individualized approach Recommends treatment, particularly in younger individuals and those with specific risk factors Reinforces the importance of considering individual factors and the potential benefits of treatment in certain cases American College of Physicians (2019)55 Does not recommend routine screening or treatment unless symptoms are present Recommends treatment Emphasizes individualizing treatment based on patient factors American Academy of Family Physicians (2021)54 Does not recommend routine screening or treatment unless symptoms are present Recommends treatment Highlights the lack of evidence for routine screening and treatment in patients without symptoms TSH = thyroid-stimulating hormone
In this issue
Jump to section
- Article
- ABSTRACT
- PRIMARILY A LABORATORY DIAGNOSIS
- COMMON IN THE ELDERLY
- MANY FACTORS AFFECT TSH LEVELS
- IS THE UPPER LIMIT OF NORMAL FOR TSH TOO HIGH?
- WHY DOES TSH RISE WITH AGE?
- IS SUBCLINICAL HYPOTHYROIDISM HARMFUL? IS TREATMENT BENEFICIAL?
- HARMS OF OVERTREATMENT
- GUIDELINES AND RECOMMENDATIONS
- MANAGEMENT CHALLENGES
- PHYSICIAN DECISION-MAKING AND ALTERNATIVES
- A PERSONALIZED APPROACH
- DISCLOSURES
- Acknowledgments
- REFERENCES
- Figures & Data
- Info & Metrics