Abstract
OBJECTIVE: Nutrition and exposure to various chemicals, including environmental pollution, insecticides, and plant phytoestrogens (having oestrogen-like effects), are environmental factors that affect puberty onset. The aim of this study was to identify the effects of propolis, which has been reported to have oestrogenic effects, on precocious puberty and the reproductive system in prepubertal female rats (ovary, endometrium, breast). METHODS: Thirty-four 25-day-old, prepubertal, female Sprague-Dawley rats were included. Rats were randomly divided into the propolis (n=17) and control groups (n=17). The primary endpoint was the number of rats that developed vaginal opening, a sign of puberty, at 12-day follow-up. In addition, the effect of propolis on ovary, uterus and breast tissue was evaluated histologically. RESULTS: Vaginal patency occurred earlier (about 7.5 days sooner) in the propolis group and all animals in the propolis group had vaginal patency by day 12. The number of ovarian follicles (in all follicles), endometrial thickness, and mammary gland secretory gland area were significantly higher in the propolis group than in the control group (all p<0.001). In addition, Ki-67 activity in the endometrium, breast tissue and ovary was more intense in the propolis group compared to the control group (all p<0.001). CONCLUSION: Propolis triggers precocious puberty in female rats, possibly by interacting with the oestrogen receptor. The mechanism of action of propolis should be considered before prescribing it. In addition, further studies are needed to explore the mechanism of action of propolis and to determine the component of propolis that triggers puberty.