Effect of T-shaped progesterone-releasing system on contraceptive efficacy and menstrual cycle regularity in Japanese monkeys.

Twenty-seven sexually mature Japanese monkeys (Macaca fuscata fuscata) weighing 6 to 8 kg were used to evaluate and characterize the local and systemic effects of a T-shaped progesterone-releasing system (UTS) following transabdominal insertion into the uterus. None of five experimental animals conceived, while four of five sham-operated control animals and all intact animals conceived. The general physical appearance, behavior, and clinical blood chemical titer of animals receiving the UTS were comparable with those of the sham-operated group. The UTS also had no significant effect on the cyclic vaginal smear pattern and serum luteinizing hormone (LH) surge during the ovulatory interval. The time course of radioactivity, determined in serum obtained serially following intrauterine insertion of a tritiated UTS, revealed the immediated appearance of 3H in serum, and the levels increased rapidly and remained high for 1 to 1.5 months. The LH release pattern in peripheral blood induced by the intravenous injection of 100 mug of LH-releasing hormone was not affected by the device in utero. The UTS did not appear to interfere with systemic function; when placed in the uterine cavity, the UTS appears to release steroid locally and to exert its antifertility effect without affecting the hypothalamic-pituitary-ovarian axis. A characteristic of the UTS is its effectiveness, since it has both mechanical and hormonal contraceptive properties.