Suppression of luteal phase, but not midcycle, prolactin levels by chronic follicular phase opiate antagonism.
OBJECTIVE
To investigate whether establishment and maintenance of chronic opioid blockade throughout the follicular phase of the menstrual cycle influences midcycle and luteal phase prolactin levels.


METHODS
Randomized, double-blind, crossover study.


METHODS
Academic research environment.


METHODS
Volunteers, aged 21-35 years, with regular menstrual cycles.


METHODS
Naltrexone (50 mg) or placebo were administered on cycle days 2-14. Blood samples were obtained in the early follicular phase and in the periovulatory and midluteal phases of the menstrual cycle.


METHODS
Serum prolactin levels.


RESULTS
In the early follicular phase, serum prolactin levels were equivalent in naltrexone (12.0 +/- 2.7 microgram/L; mean +/- SE) and placebo (12.1 +/- 2.9 micrograms/L) cycles. A statistically significant increase in serum prolactin was observed on the day of the LH surge (naltrexone: 22.6 +/- 3.7 micrograms/L; placebo: 21.7 +/- 2.7 micrograms/L; P < 0.05 versus early follicular phase), but no difference between treatments was observed. However, midluteal prolactin levels were statistically significantly lower in naltrexone cycles compared with placebo cycles (12.6 +/- 3.3 versus 15.4 +/- 3.0 micrograms/L; P < 0.05).


CONCLUSIONS
Chronic blockade of opioid activities during the follicular phase does not affect midcycle prolactin increments, but withdrawal of opioid blockade may enhance opioid effects on prolactin levels in the luteal phase.
Brzyski
R G
RG
Howard and Georgeanna Jones Institute for Reproductive Medicine, Department of Obstetrics and Gynecology, Eastern Virginia Medical School, Norfolk, USA.
Viniegra
A
A
Archer
D F
DF
D000328:Adult; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005260:Female; D005498:Follicular Phase / Q000187:drug effects*; D006801:Humans; D008183:Luteal Phase / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000378:metabolism; D009271:Naltrexone / Q000008:administration & dosage / Q000494:pharmacology*; D009292:Narcotic Antagonists / Q000008:administration & dosage / Q000494:pharmacology*; D010919:Placebos; D011388:Prolactin / Q000097:blood*; D012016:Reference Values
D009292:Narcotic Antagonists; D010919:Placebos; D009271:Naltrexone; D011388:Prolactin; D007986:Luteinizing Hormone