The effects of safflower (Carthamus tinctorius) extract on thyroid gland activity in rats

Safflower (Carthamus tinctorius) has a long history in traditional medicine. It contains a wide range of useful compounds such as flavonoids. In this study, the effect of safflower extract on thyroid gland activity was investigated.
60 male Wistar rats were studied in four groups. The negative control was left untreated while three experimental groups intra-peritoneally received 100, 200 and 300 mg/kg B.W. of safflower hydroalcoholic extract for 28 days. The serum levels of T3, T4, FT3, FT4 and TSH were measured by radioimmunoassay method on 14th and 28th days of study.   
The findings showed that short-term use of the extract directly affects thyroid function as the levels of thyroid hormones are decreased significantly, whereas it has no significant effect on TSH since its mean serum concentration remained unchanged. The long-term use of this extract did not show any significant effect, confirming that during the long run, the negative feedback on the thyroid is removed and this gland becomes adapted to some effective compound (s) present in Safflower.
The continuous short-term use of the safflower can decrease the level of thyroid hormones temporarily, while in the long term, it does not show the same effect.