Interpretation of Thyroid Function Tests
Your Results Are Normal
Your thyroid function tests show completely normal thyroid status that requires no intervention. Your TSH of 1.7 mIU/L sits comfortably in the middle of the normal reference range (0.45-4.5 mIU/L), and both your T4 (15.5 µg/dL) and T3 (240 ng/dL) are within normal limits 1.
Understanding Your Individual Thyroid Set Point
Each person has a unique thyroid "set point" where their TSH, T4, and T3 naturally settle, and your values indicate you are functioning at your personal optimal level 2, 3.
Your TSH of 1.7 mIU/L is very close to the geometric mean TSH of 1.4 mIU/L found in healthy, disease-free populations, which is the most physiologically normal value 1.
Individual variations in thyroid function are remarkably narrow—your personal normal range is approximately half the width of the laboratory reference range 2. This means your current values likely represent your stable baseline.
Why No Action Is Needed
TSH has 98% sensitivity and 92% specificity for detecting thyroid dysfunction, making a normal TSH result highly reliable for excluding both overt and subclinical thyroid disease 1.
The combination of normal TSH with normal T4 and T3 definitively excludes both hypothyroidism and hyperthyroidism 1.
Your T3/T4 ratio falls within the expected range for euthyroid individuals (normal ratio ≈15.89), further confirming normal thyroid function 4.
When to Recheck
Asymptomatic individuals with normal thyroid function tests do not require routine screening intervals—recheck only if symptoms develop 1.
Symptoms warranting repeat testing include unexplained fatigue, significant weight changes, temperature intolerance, palpitations, or cognitive changes 1.
If you remain asymptomatic, there is no need for follow-up thyroid testing unless clinical circumstances change 1.
Important Context
TSH values naturally fluctuate by up to 40-50% due to pulsatile secretion, time of day, and physiological factors—this is completely normal 1, 2.
Transient TSH changes can occur with acute illness, certain medications, or recent iodine exposure, but your stable mid-range value suggests none of these factors are present 1.