[Influence Factors on Serum Thyroid Hormone Level in Healthy People]

To explore the influences of age, gender and season on serum thyroid stimulating hormone level and thyroid hormone level in healthy people.

There were 2 564 healthy volunteers enrolled in this study, whom were divided into different groups according to gender, age and the season. The levels of serum TSH, T3, T4, FT3, FT4 were measured and the data were statistically analyzed.

The level of serum TSH in both young and middle-age groups of female was higher than that in the same age groups of male. The serum levels of T3, FT3, FT4 in both young and middle-age groups of female were lower than those in the same age groups of male (P < 0.05). In female, the serum level of TSH was increasing with age. However, the serum levels of FT3, FT4 had the opposite tendency. The level of serum FT3 in young group was higher than that in elderly group of, but T4 were lower. Lower levels of TSH, T3, FT4 were found in summer instead of winter (P < 0.05) and there was no significant difference of FT3 between that two seasons. The levels of serum TSH, T3, T4 and FT4 were correlated with seasons (r = 0.079, 0.092,-0.137, 0.140).

The levels of serum TSH and thyroid hormones are influenced by age, gender and seasons, which needs to be considered for the diagnosis of thyroid diseases and evaluation of thyroid function.