Oral contraceptives and pituitary response to GnRH: comparative study of progestin-related effects

Progesterone receptor ligands for the treatment of endometriosis: the mechanisms behind therapeutic success and failure

BACKGROUND

Despite intense research, it remains intriguing why hormonal therapies in general and progestins in particular sometimes fail in endometriosis.

OBJECTIVE AND RATIONALE

We review here the action mechanisms of progesterone receptor ligands in endometriosis, identify critical differences between the effects of progestins on normal endometrium and endometriosis and envisage pathways to escape drug resistance and improve the therapeutic response of endometriotic lesions to such treatments.

SEARCH METHODS

We performed a systematic Pubmed search covering articles published since 1958 about the use of progestins, estro-progestins and selective progesterone receptor modulators, to treat endometriosis and its related symptoms. Two reviewers screened the titles and abstracts to select articles for full-text assessment.

OUTCOMES

Progesterone receptor signalling leads to down-regulation of estrogen receptors and restrains local estradiol production through interference with aromatase and 17 beta-hydroxysteroid dehydrogenase type 1. Progestins inhibit cell proliferation, inflammation, neovascularisation and neurogenesis in endometriosis. However, progesterone receptor expression is reduced and disrupted in endometriotic lesions, with predominance of the less active isoform (PRA) over the full-length, active isoform (PRB), due to epigenetic abnormalities affecting the PGR gene transcription. Oxidative stress is another mechanism involved in progesterone resistance in endometriosis. Among the molecular targets of progesterone in the normal endometrium that resist progestin action in endometriotic cells are the nuclear transcription factor FOXO1, matrix metalloproteinases, the transmembrane gap junction protein connexin 43 and paracrine regulators of estradiol metabolism. Compared to other phenotypes, deep endometriosis appears to be more resistant to size regression upon medical treatments. Individual genetic characteristics can affect the bioavailability and pharmacodynamics of hormonal drugs used to treat endometriosis and, hence, explain part of the variability in the therapeutic response.

WIDER IMPLICATIONS

Medical treatment of endometriosis needs urgent innovation, which should start by deeper understanding of the disease core features and diverse phenotypes and idiosyncrasies, while moving from pure hormonal treatments to drug combinations or novel molecules capable of restoring the various homeostatic mechanisms disrupted by endometriotic lesions.

Omitting the first oral contraceptive pills of the cycle does not automatically lead to ovulation

OBJECTIVE

Our purpose was to test the hypothesis that omitting the first three pills of the contraceptive cycle leads to ovulation.

STUDY DESIGN

Ninety-nine women, randomly assigned to 1 of 3 treatments of combined oral contraceptives, completed the study. Treatments contained ethinyl estradiol and either monophasic gestodene, triphasic gestodene, or monophasic desogestrel. Pituitary-ovarian activity was monitored by ultrasonography of the ovaries and assay of serum concentrations of estradiol, progesterone, and follicle-stimulating hormone over 1 normal cycle (study period 1) and 1 cycle after an extended pill-free interval of 10 days (study period 2).

RESULTS

None of the women experienced normal ovulation as evaluated by ultrasonography and serum progesterone concentrations. However, follicle-stimulating hormone reached a maximal serum concentration in most women during the first 7 pill-free days, indicating complete pituitary recovery, and increases in serum estradiol concentrations were seen in each woman although with marked interindividual variation. During study period 2 we found follicles of >18 mm in 24%, 24%, and 40% of the monophasic gestodene, triphasic gestodene, and monophasic desogestrel groups, respectively.

CONCLUSIONS

Follicular growth up to preovulatory size is common in women missing the first one to three pills of their contraceptive cycle. Although this creates the prerequisite for ovulation, normal ovulation did not occur when pill omissions were limited to only 3 days.

The response of the pituitary-ovarian axis to pulsatile administration of gonadotropin-releasing hormone in long-term oral contraceptive users

OBJECTIVE

Our purpose was to differentiate between pituitary and hypothalamic feedback effects of oral contraceptives.

STUDY DESIGN

Twenty micrograms of gonadotropin-releasing hormone was administered intravenously at 90-minute intervals for 4 days to 14 long-term users of a combined oral contraceptive (30 micrograms of ethinyl estradiol and 150 micrograms of levonorgestrel), starting at different moments in the pill cycle. On the fourth day of administration the pulsatile release of luteinizing hormone was determined by blood sampling every 10 minutes for 6 hours. The sensitivity of the pituitary was determined before, during, and after treatment with gonadotropin-releasing hormone by a 100 micrograms gonadotropin-releasing hormone challenge test. On each sampling day serum estradiol, progesterone, and prolactin levels were measured, and ovarian ultrasonography was performed.

RESULTS

After 4 days of pulsatile gonadotropin-releasing hormone administration every exogenous gonadotropin-releasing hormone bolus was followed by an endogenous luteinizing hormone pulse of high amplitude (median 3.30 U/L). Both serum luteinizing hormone and follicle-stimulating hormone levels increased significantly (p < 0.001). The increase in follicle-stimulating hormone levels was accompanied by an increase in serum estradiol (p < 0.01). The luteinizing hormone response to a 100 micrograms bolus of gonadotropin-releasing hormone decreased during gonadotropin-releasing hormone treatment (p < 0.01), whereas the follicle-stimulating hormone response did not change.

CONCLUSION

Pituitary sensitivity is not impaired during oral contraceptive use, suggesting that oral contraceptives exert their negative feedback effects predominantly at the hypothalamic level.