Blankstein, J., Reyes, F. I., Winter, J. P. D., & Faiman, C. (1981). Endorphins and the regulations of the human menstrual cycle. Clinical endocrinology, 14(3), 287-294. https://doi.org/10.1111/j.1365-2265.1981.tb00197.x
Blankstein J, Reyes FI, Winter JPD, Faiman C. Endorphins and the regulations of the human menstrual cycle. Clin Endocrinol (Oxf). 1981;14(3):287-294. doi:10.1111/j.1365-2265.1981.tb00197.x
Blankstein, Josef, et al. "Endorphins and the regulations of the human menstrual cycle." Clinical endocrinology, vol. 14, no. 3, 1981, pp. 287-294.
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In order to assess a possible influence of endogenous opioids upon gonadotrophin secretion in women, we examined the effects of i.v. administration of 10 mg naloxone, a specific opiate antagonist, in ten normal menstruating women, in thirteen women with amenorrhoea and/or hyperprolactinaemia and in two women with putative deficiency of gonadotrophin-releasing hormone (GnRH). In thirteen subjects, a saline vehicle control study (randomized order of administration) was also performed. In the normal women, naloxone failed to elicit changes in serum gonadotrophin levels when administered during the early follicular phase of the menstrual cycle. However, significant increments of LH were observed from 30 to 165 min following naloxone administration during the late follicular phase. Similar LH responses occurred in the amenorrhoeic and hyperprolactinaemic women. There was a tendency towards a concomitant increment in FSH levels, which reached statistical significance variably from 60 to 105 min post-naloxone. The LH response to naloxone in individual subjects showed a significant (P less than 0.01) quadratic (U-shaped) relationship to the log basal oestradiol concentration. No response to naloxone was observed in the two patients with GnRH deficiency despite a brisk response to an exogenous GnRH bolus. Taken together, these data suggest that central nervous system inhibitory opioid pathways may be involved in the regulation of LH secretion in normal women and that excessive production of endogenous opioids may play a role in the pathophysiology of some amenorrhoeic conditions.
One hundred fifty-six women with cycle disorders presenting as absence or infrequency of ovulation and with luteal phase deficiency (group II, according to the World Health Organization classification) received clomiphene citrate (CC) for ovulation induction. The administered dosage ranged from 50 to 250 mg/d. The follicular development in terms of numbers of small (less than 8 mm), intermediate (9 to 15 mm), and large (greater than 15 mm) follicles and their distribution in either one or both ovaries on the day of assumed ovulation was related to the dosage of CC. A statistically significant increase was found in the total number of follicles in relation to the dosage of CC (P less than 0.003). In view of the development of the mature follicles, the gradual increase in CC daily dosage was thought to be associated with additional mature follicles before ovulation. However, this increased follicular recruitment was not regarded as statistically significant. Treatment with low doses of CC resulted in follicular development in only one ovary, whereas increased follicular recruitment after high CC dosage was found in association with follicular development in both ovaries.
A prospective study of six unselected couples diagnosed as having unexplained infertility was done. In three of six patients, subtle abnormalities in follicular development were detected. In the first case poor follicular growth was observed. There was a premature small rise of luteinizing hormone (LH) with subsequent low levels of estradiol (E2) in the late follicular phase and unusual wide LH peak. This was followed by low progesterone levels in the luteal phase. In the second case follicular growth was abrupted by premature LH surge. This surge was triggered by early rise of E2 level while the follicle was still small in size. In the third case luteinized unruptured follicle syndrome was diagnosed, on ultrasound examination. All of the abnormalities were repetitive.
The possibility that beta-endorphin, an endogenous opiate, is involved in the regulation of the menstrual cycle was examined. Daily serum beta-endorphin levels, in conjunction with luteinizing hormone, progesterone, and 17 beta-estradiol were measured during 26 hormonally normal menstrual cycles. Twenty-one cycles showed a preovulatory peak and postovulatory trough of beta-endorphin, 2 cycles had a postovulatory peak, and 3 had a postovulatory peak with sustained elevation. The raw data were standardized by conversion to "Z-scores," and the composite values were computed for each of the three classes described above. Significance within these three classes was assessed using a one-way analysis of variance with an F-ratio at 95% confidence limits. The composite plot of the 26 cycles showed a statistically significant preovulatory peak occurring 2 days prior to the luteinizing hormone surge and a postovulatory trough of beta-endorphin 5 days later. These results suggest that beta-endorphins play a significant role in the neurochemical mechanisms of gonadotropin release.
To test the postulate that endogenous opioid peptides may be involved in the neuroendocrine mechanisms controlling the frequency and amplitude of LH pulses, saline and an opioid receptor antagonist, naloxone, were infused sequentially, each for 6-h intervals, in six normal cycling women during the luteal phase of the menstrual cycle. During naloxone infusion (1.6 mg/h), there was a significant (P less than 0.01) increase in both the frequency and amplitude of LH pulses compared to those in saline controls. FSH pulses were not discernible in individual subjects; however, a significant increment in FSH levels occurred concomitantly with the increase in LH. These data strongly suggest that endogenous opiates, through an inhibition of hypothalamic LRF, participate in the endocrine events leading to the low frequency of episodic LH secretion characteristic of the luteal phase of the human menstrual cycle.
Substantial evidence now exists to indicate that the endogenous hypothalamic opioidergic mechanism(s) represents one of the important controlling systems for release of gonadotropin-releasing hormone. Modulations of frequency and amplitude of the secretory activity of gonadotropin-releasing hormone appears to be mediated through an inhibitory action of endogenous opioids, and the functional coupling of the opioidergic and gonadotropin-releasing hormone systems is an ovarian steroid-dependent event. There is also evidence to implicate suprahypothalamic mechanism(s) that enhance endogenous opioid inhibition of secretion of gonadotropin-releasing hormone. Although exogenous opioid peptides and their synthetic analogs consistently induce the secretion of prolactin, blockade of opioid receptors in humans by naloxone failed to elicit a decrement in the levels of prolactin under a variety of conditions. On the contrary, naloxone induced a remarkable increment in the secretion of prolactin via an increased frequency of pulsatile release which is synchronized with pulses of luteinizing hormone. These observations suggest that a common neuroendocrine mechanism is involved in the opioidergic control of the secretion of both luteinizing hormone and prolactin in women.
beta-Endorphin has a role in the regulation of the normal menstrual cycle and possibly in the onset of puberty. We have reviewed the evidence pointing to an alteration in this neuropeptide that may contribute to the pathogenesis of various reproductive dysfunctions. Elevated or high levels of beta-endorphin have been associated with exercise-associated amenorrhea, stress-associated amenorrhea, and polycystic ovarian syndrome. Depressed or low levels of beta-endorphin have been associated with PMS and menopause. Alterations in the levels of beta-endorphin may change the pulsatile release of GnRH via noradrenergic and/or dopaminergic pathways. We have primarily focused on beta-endorphin as representative of the endogenous opioid peptides, but other opioid peptides may also contribute to the pathogenesis of various types of reproductive dysfunction. Perhaps it will become possible to characterize and hone our understanding of the function of beta-endorphin and the other substances composing the endogenous opioid peptides. A better understanding of their role in physiological as well as pathophysiological processes may allow for the development of rational approaches to the treatment of specific disorders pertaining to reproduction. Many questions remain unanswered. Among the most relevant are: what is the precise mechanism of action by which beta-endorphin exerts its influence on pulsatile GnRH release? Is there a functional relationship between CNS and peripheral (serum) levels of beta-endorphin? Are the detected changes in beta-endorphin levels merely associated, or are they a cause of a particular disorder? Since it took almost 40 years between the time prostaglandins were first discovered and eventual realization of their clinical application, it may take some time before the beta-endorphin story is complete.
PMID 6790206 6790206 DOI 10.1111/j.1365-2265.1981.tb00197.x 10.1111/j.1365-2265.1981.tb00197.x Blankstein et al. 1981, Blankstein 1981
Cite this article
Blankstein, J., Reyes, F. I., Winter, J. P. D., & Faiman, C. (1981). Endorphins and the regulations of the human menstrual cycle. Clinical endocrinology, 14(3), 287-294. https://doi.org/10.1111/j.1365-2265.1981.tb00197.x
Blankstein J, Reyes FI, Winter JPD, Faiman C. Endorphins and the regulations of the human menstrual cycle. Clin Endocrinol (Oxf). 1981;14(3):287-294. doi:10.1111/j.1365-2265.1981.tb00197.x
Blankstein, Josef, et al. "Endorphins and the regulations of the human menstrual cycle." Clinical endocrinology, vol. 14, no. 3, 1981, pp. 287-294.
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