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KMID : 0381219840160040289
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Journal of RIMSK
1984 Volume.16 No. 4 p.289 ~ p.295
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β-Endorphin Variations throughout the Menstrual Cycle
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Abstract
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b-Endorphin, one of the most potent of opioids, forms part of a large multifunctional precursor molecule or prohormone, termed proopiomelanocortin(POMC).
b-Endorphin is synthesized and stored principally in the anterior pituitary, which accounts for more than 99 per cent of the b-endorphin found in the central nervous system and its connections; smaller amounts can also be found elsewhere in the brain, chiefly in the hypothalamus, pancreas, and gastric antrum; it is also synthesized in the placenta. All measurements of b-endorphin-like activity in human peripheral plasma have shown that it is elevated or depressed under the same conditions as those that elevate or depress ACTH.
Physiologic actions of b-endorphin have been reported as have a wide variety of opiatelike actions on the central nervous system and affect the secretion of all pituitary hormones, including those of the posterior pituitary.
These neuroendocrine actions are a stimulation of prolactin secretion and an inhibition of gonadotropin secretion.
Opposite actions to these are noted after the administration of naloxone, a generalized opiate antagonist, suggesting that endogenously secreted opioids do have a physiologic regulatory role on pituitary hormone secretion.
Naloxone stimulation of secretion of luteinizing hormone(LH) in the human female have been shown to be dependent on the phase of the menstrual cycle, being greatest in the late follicular and midluteal phases, when estrogen levels are relatively high.
Concentrations of b-endorphin were measured in the hypophyseal portal blood at various phases of the menstrual cycle and after ovariectomy in rhesus and pigtailed monkeys.
b-Endorphin concentrations were high during the mid-to late follicular phase and luteal phase, but were undetectable at menstruation and after ovariectomy. These results indicate that b-endorphin concentrations in hypophyseal portal blood are related to menstrual cycle events, probably changes in ovarian steroids and suggests that , b-endorphin may participate in the ovarian feedback regulation of gonadotropin secretion.
The mechanism by which endogenous opioids modulate gonadotropin secretion is unclear and further investigation must be needed.
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