Effect of post-ovulatory administered oestrogens on corpus luteum function

Area of Science:

• Reproductive endocrinology
• Pharmacology

Background:

• The menstrual cycle is regulated by complex hormonal interactions, including progesterone.
• Synthetic estrogens can influence reproductive hormone profiles.

Purpose of the Study:

• To investigate the effects of diethystilboestrol (DES) and 17alpha-ethinyl-oestradiol-3-methylether (EEM) on plasma progesterone levels during the luteal phase.
• To determine if the timing of administration influences the hormonal effects.

Main Methods:

• Five women with normal menstrual cycles received daily oral doses of DES (60 mg) or EEM (30 mg) for 5 days.
• Plasma samples were collected daily for radioimmunoassay (RIA) of progesterone, estrogens, and luteinizing hormone (LH).
• Treatments were administered during specific cycles, interspersed with control cycles.

Main Results:

• DES administration lowered plasma progesterone when initiated on the day of the LH surge, but did not alter the corpus luteum phase length.
• EEM suppressed corpus luteum function in the late luteal phase if started on the LH surge day; effects were less pronounced if started later.
• Neither DES nor EEM shortened the interval between ovulation and the subsequent menstrual bleeding; EEM even delayed it.

Conclusions:

• Both DES and EEM impact luteal phase hormone levels, with effects dependent on the timing of administration relative to the LH surge.
• DES primarily affects progesterone levels, while EEM can suppress corpus luteum function and potentially delay menstruation.
• These synthetic estrogens do not shorten the luteal phase but can alter its hormonal milieu.