Effect of domestically-made levonorgestrel-releasing intrauterine device on the endocrine system and menstruation in monkeys.

Effect of domestically-made levonorgestrel-releasing intrauterine device (LNG, release rate, 6 micrograms/day) on the endocrine system and menstruation in monkeys was investigated. The results showed that the Estradiol (E2) and progesterone (P) levels were significantly decreased 2 ovulatory cycles after insertion of the devices as compared with those before insertion in 3 monkeys (P > 0.001), suggesting an evident ovulation-suppressing effect. In 1 monkey, the E2 and P levels were the same before and after insertion, and expulsion of device was found in the monkey later. The plasma LNG concentration in 3 animals was 493.69-454.60 pg/ml and plasma LNG was not detected in 1 monkey. The hormone level returned to normal level after removal of the devices.