Investigation of effects of myricetin on thyroid-gonadal axis of male rats at prepubertal period

• Thyroid-gonadal axis during peripubertal period to pubertal period was determined.
• Preputial separation was monitored beginning on post natal day 30, until all males showed separation.
• Hormonal, biochemical and hematological analysis were investigated.
• Incidence of exposure-related histopathologic lesions has been recorded.
• In the ethinyl estradiol dose groups and 25 mg/kg/day of myricetin dose group the age of onset of PPS was delayed.
• In testis tissue, the incidence of tubular atrophy increased in all treatment groups compared.
• In ethinyl estradiol and 50 mg/kg/day of myricetin dose groups, prostatic intraepithelial neoplasia (PIN) was observed.

The present study is to investigate the effects of myricetin on pubertal development and thyroid hormone concentrations in the male rat. The rats were exposed to 25 and 50 mg/kg/day of myricetin by gavage from post natal day (PND) 23 to 53. Preputial separation (PPS), organ weights and biochemical and hormone analysis were investigated. PPS was significantly delayed in low dose myricetin groups. Total serum thyroxine (T4) and, triiodothyronine (T3) levels increased in 25 mg/kg myricetin dose group but thyroid-stimulating hormone (TSH) level increased in 0.7 μg/kg/day ethinyl estradiol dose groups. Myricetin exposure did not significantly change androgen dependent tissue weights; however myricetin exposure caused congestion, germinal cell debris and tubular atrophy in testis colloidal and tubular degeneration in thyroid gland were observed while there was germinal cell debris in epididymis. This study demonstrated that orally gavages myricetin caused adverse effects on male thyroid-gonadal axis during peripubertal period to pubertal period.