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Abstract
Objectives: To assess the effect of estrogen replacement on the simultaneous blockade of the
dopaminergic (DA) and opioidergic neural control of hypothalamic-gonadotropic function
in postmenopausal women. Methods: Twenty healthy postmenopausal women, 48–55 years old were randomly assigned to receive
either a 4-h naloxone infusion at 2 mg/h (group 1, n = 7) or a 10 mg i.v. bolus of metoclopramide (group 2, n = 7) or both drugs, simultaneously (group 3, n = 6) before and after 3 weeks of transdermal estradiol (100 μg/day). Blood samples
were obtained at 30-min intervals during 4 h and duplicate determinations of serum
follicle-stimulating hormone (FSH), luteinizing hormone (LH), estradiol (E2) and prolactin (PRL) were performed in all samples. Results: In group 1 only a mild but significant LH rise after but not before estrogen replacement
was seen. In group 2 PRL had a greater rise after than before estrogen therapy, without
other hormonal changes. In group 3 a greater rise in PRL occurred after than before
estrogen administration and serum LH had a sustained rise throughout the test only
after estrogen replacement (greater than in group 1). No FSH changes were observed.
The after-estradiol PRL response was nearly similar in groups 2 and 3. Conclusions: Our results indicate that in the untreated postmenopausal women, the dopaminergic
system has little and the opioidergic system has no significant input in the control
of gonadotropin or prolactin release. However, following estrogen replacement, opioids
are involved in the inhibition of LH release and stimulating PRL release, while the
dopaminergic system acts to inhibit PRL release and modulates LH release or inhibition,
depending on the levels of circulating estrogens.
Keywords
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Article info
Publication history
Accepted:
January 20,
1997
Received in revised form:
November 18,
1996
Received:
August 13,
1996
Identification
Copyright
© 1997 Published by Elsevier Inc.
