On the mechanism of the positive feedback action of estradiol on luteinizing hormone secretion in the rhesus monkey.
Level 5 - mechanism / opinion, no new human data
Animal model experimental study (rhesus monkeys)
PubMed 9814490 · doi:10.1210/jcem.83.11.5230
What was done
Researchers tested whether the positive feedback LH surge triggered by estradiol (E2) is simply an escape from negative feedback due to gonadotrope desensitization. They administered a pure estrogen receptor antagonist (ZM 182,780) to 14 rhesus monkeys during the midfollicular phase of the menstrual cycle at a dose confirmed in separate experiments to block both negative and positive feedback actions of exogenous E2 on pituitary LH secretion.
What was found
The abstract reports no numerical values. Administration of the estrogen antagonist failed to induce a surge-like increase in serum LH concentrations. Additionally, ZM 182,780 inhibited E2-induced LH surges but failed to block the inhibitory effect of E2 on hypothalamic GnRH pulse generator activity.
Why it matters
These results clarify primate neuroendocrine physiology, showing that the preovulatory LH surge requires an active, distinct mechanism rather than passive release or desensitization from estradiol-mediated negative feedback.
Limits
The study was performed entirely in non-human primates (rhesus monkeys, n = 14), limiting direct clinical application. Specific hormone concentrations, confidence intervals, and statistical measures were not reported in the abstract.
Cited by
- supports An estrogen level sustained at 200 picograms for 50 hours signals the brain to release an LH surge.