TSH Changes With Adjustments
of Thyroxine Dosage
Adapted from a 1988 biochemical study conducted in 21 adult Caucasian patients in the United Kingdom with primary hypothyroidism who were tested on a series of different thyroxine dosages to evaluate effectiveness of measuring TSH levels to monitor thyroid function.
Following a 25 mcg Dose Change of Levothyroxine,
Most Patients Had Changes in TSH Levels6
The “optimal dose” was determined for each patient as that dosage of thyroxine being taken when the TRH response was normal (i.e., an increase in TSH between 4.7 and 25 mIU/L).
- 10 patients were dosed 25 mcg higher than their optimal dose (the dose at which each patient had a normal response to thyrotropin-releasing hormone)
- 2 patients were dosed 25 mcg lower than their optimal dose
- 9 patients were dosed 25 mcg higher and lower than their optimal dose
Biochemical assessment incorporated measurement of serum TSH, T3, and T4. TSH lower limit of quantification was 0.2 mIU/L and upper limit of normal was 5.6 mIU/L, as indicated by the shaded area. Each dot represents one patient.