From the Guidelines
A TSH level of 0.14 mIU/L is slightly below the normal reference range, suggesting possible hyperthyroidism, and requires follow-up testing, including free T4 and free T3 levels, to confirm diagnosis. This finding is based on the most recent and highest quality study available, which recommends that treatment is generally not recommended for patients with TSH levels between 0.1 and 0.45 mIU/L or when thyroiditis is the cause 1.
Key Considerations
- The condition could be caused by Graves' disease, thyroiditis, excessive thyroid medication, or other factors.
- Symptoms to monitor include unexplained weight loss, increased heart rate, anxiety, heat intolerance, and tremors.
- This low TSH occurs when the pituitary gland reduces TSH production in response to excess thyroid hormone in the bloodstream.
- The USPSTF found no direct evidence that treatment of thyroid dysfunction based on risk level alters final health outcomes 1.
Next Steps
- No immediate medication changes should be made based on this single value alone.
- If you're currently taking thyroid medication like levothyroxine, continue your current dose until evaluated by your healthcare provider.
- Schedule an appointment with your healthcare provider within the next few weeks for proper evaluation and management of this laboratory finding.
- The principal treatment for hypothyroidism is oral T4 monotherapy (levothyroxine sodium), and hyperthyroidism is treated with antithyroid medications (such as methimazole) or nonreversible thyroid ablation therapy (for example, radioactive iodine or surgery) 1.
Important Outcomes
- Important clinical outcomes include cardiovascular- and cancer-related morbidity and mortality, as well as falls, fractures, functional status, and quality of life 1.
- Intermediate biochemical outcomes are less important; they are not reliable evidence of treatment effectiveness, and the effects of treatment of thyroid dysfunction on important clinical outcomes may be independent of any known intermediate outcomes.
From the Research
Significance of Low TSH Level
A low Thyroid-Stimulating Hormone (TSH) level of 0.14 may indicate hyperthyroidism, rather than hypothyroidism. According to the study 2, hyperthyroidism is defined as a low or undetectable TSH level with elevated triiodothyronine (T3) or thyroxine (T4) values.
Definition of Hyperthyroidism
- Overt hyperthyroidism: low or undetectable TSH level with elevated T3 or T4 values 2
- Subclinical hyperthyroidism: low or undetectable TSH level with normal T3 and T4 values 2, 3
Management of Hyperthyroidism
- Antithyroid drugs (e.g., propylthiouracil, methimazole) or definitive therapies (e.g., radioactive iodine ablation, thyroidectomy) can be used to manage overt and subclinical hyperthyroidism 2
- Treatment for subclinical hyperthyroidism is recommended for patients 65 years or older with TSH levels lower than 0.10 mIU/L, or for symptomatic patients or those with cardiac or osteoporotic risk factors 2
Relationship Between TSH and Cortisol
- A positive relationship between TSH and cortisol levels has been found in healthy young individuals, suggesting that TSH levels > 2.0 uIU/L may be abnormal 4
Measurement of TSH
- Different automated immunoassays may produce varying TSH values, highlighting the need for harmonization of methods to meet clinical requirements and avoid misdiagnosis 5