Pituitary, ovarian and endometrial effects of 300 micrograms norethisterone and 30 micrograms levonorgestrel administered on cycle days 7 to 10.

The ovarian, endometrial and pituitary effects of 300 micrograms norethisterone (NET) and 30 micrograms levonorgestrel (L-NOG) administered orally on cycle days 7-10 were investigated in two groups of 10 women each, by daily analysis of plasma estradiol (E2), progesterone (PROG), immunoreactive luteinizing hormone (LH) and follicle stimulating hormone (FSH) in a pretreatment control cycle and during NET or L-NOG administration. Endometrial biopsies were obtained for morphometric analysis on cycle day 11 in the control and treatment cycles. Treatment with 300 micrograms NET resulted in an increase in the area under the E2 peak (p less than 0.05), reduction in the number of subjects with normal progesterone profile (p less than 0.05) and a decrease in the area under the progesterone curve (p less than 0.05). The treatment suppressed the LH peak in 4 subjects and progesterone in 4 subjects. The follicular phase was prolonged in one subject. Norethisterone induced marked subnuclear vacuolation in the endometrium, while the glandular mitoses were decreased during NET treatment. Treatment with 30 micrograms L-NOG resulted in a decrease in subjects with normal progesterone profiles (p less than 0.05) and in the area under the progesterone curve (p less than 0.05). The treatment suppressed the LH peak in 3 subjects and progesterone in 4 women. The follicular phase was prolonged in one subject. L-NOG did not significantly increase the diameter of glands or induce subnuclear vacuolation in the endometrial glands.