A large laboratory data-based have shown that there is a significant circadian variation in the TSH levels with peak levels occurring between midnight and 8 am and nadir levels between 10 am–3 pm and 9–11pm. Although the TSH secretion is pulsatile, the low amplitude of the pulses and the long half-life of TSH result in only modest variations in blood levels.

In your opinion does time of sampling or food intake alter thyroid function test?