since enhanced T4 to T3 conversion maintains normal T3 concentrations until hypothyroidism becomes severe. Patients with NTI or caloric deprivation typically have low total and free T3 values.

In people with subclinical hyperthyroidism, the thyroid produces normal levels of T4 and T3. Yet, the person will have lower-than-normal TSH levels. This imbalance of hormones leads to the condition.