Suppression of ovarian function by Microgynon 30 in day 1 and day 5 "starters".

The suppression of ovulation during the first treatment cycle with Microgynon 30 (150 micrograms levonorgestrel and 30 micrograms ethinyl oestradiol) for nine subjects starting the "pill" on day 1 of their cycle and five subjects on day 5 was investigated. Serum oestradiol and progesterone levels throughout the cycle and midcycle urinary LH levels were reliably suppressed in all day 1 "starters". Serum progesterone levels and urinary LH levels were also suppressed in day 5 "starters" but one subject produced oestradiol levels within the normal range of ovulatory cycles. Mean oestradiol levels of day 5 "starters" were found to be significantly higher than those of day 1 "starters" (p less than 0.05).