Interpretation of Thyroid Function Tests in a 31-Year-Old Female
These thyroid function test results are completely normal and require no intervention. 1, 2
Understanding Your Test Results
Your thyroid function tests show:
- TSH 0.894 mIU/L - This falls well within the normal reference range of 0.45-4.5 mIU/L, with a geometric mean of 1.4 mIU/L in healthy populations 1
- T4 11.3 - Assuming this is in µg/dL (typical units), this is within the normal range of approximately 4.5-12 µg/dL 3
- T3 uptake 20% - This is an older test that measures binding protein capacity, not actual T3 hormone levels; when combined with T4, it helps calculate the free T4 index 3
Clinical Significance
The combination of normal TSH with normal T4 definitively excludes both overt and subclinical thyroid dysfunction. 1 Your TSH value of 0.894 mIU/L is close to the population geometric mean of 1.4 mIU/L, indicating optimal thyroid function 1.
Why TSH is the Key Test
- TSH is the most sensitive screening test for thyroid dysfunction, with sensitivity above 98% and specificity greater than 92% 1
- TSH responds with logarithmically amplified variation to even minor changes in thyroid hormone levels, making it an extremely sensitive marker 4
- A normal TSH effectively rules out primary hypothyroidism and hyperthyroidism in the vast majority of cases 3
Individual Variation Considerations
While your results are normal by population standards, it's important to understand that each person has their own unique thyroid "set point" 4:
- Individual 95% confidence intervals for thyroid tests are approximately half the width of population reference ranges 4
- Your personal normal TSH range may be narrower than the laboratory reference range of 0.45-4.5 mIU/L 4
- However, a TSH of 0.894 mIU/L with normal T4 indicates you are currently euthyroid (normal thyroid function) 1, 4
When to Recheck Thyroid Function
You do not need routine thyroid screening if you remain asymptomatic. 1 Recheck thyroid function only if you develop:
- Unexplained fatigue or weakness 1
- Unintentional weight changes 1
- Temperature intolerance (feeling too hot or too cold) 1
- Changes in heart rate or palpitations 1
- Hair loss, skin changes, or menstrual irregularities 1
- New risk factors such as pregnancy planning 1
Important Caveats
- TSH values can be transiently affected by acute illness, certain medications, recent iodine exposure (such as from CT contrast), or stress 1, 2
- If thyroid testing was performed during illness or hospitalization, results may not reflect your true baseline thyroid status 1
- A single set of normal results does not require confirmation testing unless symptoms develop 1
In summary, your thyroid function is normal, and no treatment or further testing is needed at this time unless symptoms develop. 1, 3