Opioid control of LH secretion in humans: menstrual cycle, menopause and aging reduce effect of naloxone but not of morphine

Current pharmacotherapy and future directions for neuroendocrine causes of female infertility

INTRODUCTION

Infertility is recognized as a major global health issue, often associated with significant psychological distress for affected couples. Causes of female infertility include endocrine conditions leading to oligo/anovulation, in addition to structural causes such as tubal, uterine, or peritoneal disorders. Pharmacological treatments, targeting pathways in the hypothalamic-pituitary-ovarian axis, can improve rates of ovulation, conception, pregnancy, and birth. Some existing therapeutic options are hindered by limited efficacy or by a non-physiological mechanism, which can risk excessive stimulation and treatment-related adverse effects. Therefore, there is a continued need for novel therapies to improve care for patients suffering with infertility.

AREAS COVERED

In this review, the authors focus on endocrine causes of oligo/anovulation in women and on advances in assisted reproductive technology. Current pharmacological treatments and putative future therapeutic avenues in development to aid fertility in women are outlined.

EXPERT OPINION

A deeper understanding of the reproductive neuroendocrine network governing hypothalamic gonadotropin-releasing hormone release can offer novel therapeutic targets for the treatment of female subfertility, leading to improved clinical outcomes, less invasive routes of administration, and decreased treatment-related side-effects. The ultimate aim of development in female subfertility is to offer therapeutic interventions that are effective, reproducible, associated with minimal risks, and have an acceptable route of administration.

Prescription Opioid Use Among Populations of Reproductive Age: Effects on Fertility, Pregnancy Loss, and Pregnancy Complications

Prescription opioid use is common among men and women of reproductive age, including during assisted-reproduction procedures. Opioid use disorder and chronic use are associated with harms to fertility and pregnancy outcomes, but it is unclear whether these associations extend to common short-term patterns of prescription opioid use. We conducted a literature review using PubMed, Embase, Web of Science, and Scopus to identify studies of nonchronic, nondependent opioid use and reproductive endpoints including fertility, pregnancy loss, and pregnancy complications (i.e., preterm birth, birth weight, gestational diabetes, and hypertensive disorders of pregnancy). Seventeen studies were included. Although results of the studies suggest possible harms of short-term opioid use on fertility and pregnancy loss, methodologic limitations and the small number of studies make the literature inconclusive. This review highlights important data gaps that must be addressed to make conclusions about potential reproductive effects of short-term opioid use. These include the need for additional data on opioid use before clinically recognized pregnancy; accurate measurement of opioid exposure by multiple means with detailed information on the types and quantity of opioids used; assessment of important confounders, including opioid use indication, comorbidities, and use of other medications and substances; and studies of paternal opioid use, fertility, and pregnancy outcomes. A primary limitation of this review targeting studies of nonchronic opioid exposure is the possibility that selected studies included populations with unspecified chronic or dependent opioid use. Efforts to understand the impact of the prescription opioid epidemic should address potential reproductive harms of these medications among people of reproductive age.

Functional hypothalamic and drug-induced amenorrhea: an overview

BACKGROUND

Functional hypothalamic amenorrhea (FHA) is a form of chronic anovulation not due to identifiable organic causes and with adverse health consequences. The identification of women with this disorder or the precocious identification of women at risk is based on the knowledge of lifestyle risk factors or behaviors such as stress, weight loss, and excessive physical exercise that are known to negatively impact gonadal axis activity.

METHODS

In this overview, we described the most common forms of FHA, in particular stress-induced amenorrhea and overtraining-induced amenorrhea. In addition, although its mechanisms can differ from those involved in FHA, we reviewed the available literature on drug-induced amenorrhea, highlighting the clear connection between this condition and psychoactive drugs such as antipsychotics, antidepressants and anti-epilectics thus raising concern about the role that the abuse of substances such as opioids or alcohol can possibly have on the growing unexplained infertility of the female population.

Safety concerns with long-term opioid use

INTRODUCTION

The benefits of opioid therapy must be balanced by any adverse effects. In recent years, prescription opioids have been increasingly prescribed, but have also been associated with increased abuse, overdose and death.

AREAS COVERED

This review will categorize the common risks of opioid administration. Recognized adverse effects of opioid therapy include constipation, tolerance, endocrinopathies, sleep disorders, cognitive effects, respiratory depression, overdose and addiction. Studies have shown that there is increased risk of overdose and death with higher daily opioid doses, particularly above a morphine equivalent oral daily dose of 100 milligrams. Extended-release/long acting (ER/LA) opioid formulations may be beneficial for the compliant patient, yet may expose a higher risk for abuse if used inappropriately since each tablet carries a larger dose of medication.

EXPERT OPINION

Prospective, controlled one-year trials are needed to establish the efficacy and safety profile of chronic opioid therapy. In addition to the well known side effects of chronic opioid therapy, the influence and serious effect of opioids on sleep and central sleep apnea is only recently being investigated. The lowest possible daily opioid must be used to manage chronic pain, and all clinicians should be cautious in the use of daily morphine equivalent doses above 50-100 milligrams.

Effects of estrogen and opioid blockade on blood pressure reactivity to stress in postmenopausal women

Estrogen may influence coronary heart disease risk in women through the effects of endogenous opioids on autonomic control of blood pressure. In a randomized, placebo-controlled trial, we examined the combined effects of estrogen and the opioid antagonist, naltrexone, on blood pressure responses to psychological stress in 42 postmenopausal women. After 3 months of estrogen or estrogen plus progestin (hormone replacement therapy; n = 27) or placebo replacement, participants completed a mental arithmetic task after administration of .7 mg/kg oral naltrexone or placebo. Systolic blood pressure (SBP), diastolic blood pressure, mean arterial pressure and heart rate (HR) were measured at rest and during the arithmetic stressor. Stress produced significant increases in circulatory measures regardless of estrogen condition or opioid blockade (p's < .001). Interestingly, there was an estrogen by naltrexone interaction on SBP reactivity scores [F(1,38) = 4.36, p < .05], where women on estrogen with intact opioid receptors showed the largest SBP responses to stress, compared with all other conditions. This is consistent with some studies of premenopausal women, suggesting that estrogens may alter opioid function during stress. The interaction between estrogen and endogenous opioids may explain sex differences in opioid effects on stress reactivity in younger premenopausal women.

Activity anorexia: An interplay between basic and applied behavior analysis

The relationship between basic research with nonhumans and applied behavior analysis is illustrated by our work on activity anorexia. When rats are fed one meal a day and allowed to run on an activity wheel, they run excessively, stop eating, and die of starvation. Convergent evidence, from several different research areas, indicates that the behavior of these animals and humans who self-starve is functionally similar. A biobehavioral theory of activity anorexia is presented that details the cultural contingencies, behavioral processes, and physiology of anorexia. Diagnostic criteria and a three-stage treatment program for activity-based anorexia are outlined. The animal model permits basic research on anorexia that for practical and ethical reasons cannot be conducted with humans. Thus, basic research can have applied importance.

Opioid-induced biochemical alterations of the neuroendocrine axis

Exogenous opioids have been used for decades to palliate cancer-related pain and other cancer-related manifestations and, more recently, to treat patients with pain not related to oncologic disease. While the goal of opioid treatment is symptomatic relief and improved quality of life, these patients often suffer from adverse side effects, including endocrine system abnormalities, of which hypogonadism is the best known. Opioids may interact with other hypothalamic-pituitary pathways and endocrine end organs, and in most cases these interactions are subtle and the effects unclear. The long-term effects of these agents on the endocrine system are still largely unknown. This article discusses the various effects of opioid agents on the endocrine system and provides information that allows early recognition of side effects that may alter the quality of life of patients affected by pain, awareness of the potential complications in opioid addicts, and detection and treatment of side effects in participants of an opioid detoxification program.

Opioids in chronic non-cancer pain

INTRODUCTION

The use of chronic opioid therapy for chronic non-cancer pain is growing and is now accepted as an effective treatment modality.

AREAS COVERED

Although there are guidelines and reviews for chronic opioid therapy for chronic non-cancer pain patients, physicians may still have concerns and be reluctant to prescribe strong opioids for chronic non-cancer pain. Common issues and concerns when prescribing opioid for chronic pain management are reviewed and discussed. The literature search was done using Medline with key words 'chronic non-cancer pain', 'chronic opioid therapy', 'effectiveness', 'opioid tolerance', 'opioid-induced hyperalgesia', 'adverse effect', 'opioid dependency', 'addiction', 'monitoring', 'opioid contract' and various combinations with these key words. Studies from 1990 - 2010 have been included. This article helps readers to update, clarify and understand the common concerns when using opioid for chronic non-cancer pain. Clinical effectiveness and adverse effects with chronic opioid therapy, opioid tolerance and opioid-induced hyperalgesia, opioid dependency and addiction, monitoring during chronic opioid use, and opioid contact are discussed in detailed.

EXPERT OPINION

Not much strongly positive data supports the long-term use of opioids for pain relief, and the evidence for an improvement in functional activity is inconclusive. With careful selection of patients, meticulous prescription and monitoring protocol, chronic non-cancer pain patients who are likely to benefit from potent opioids should not be prevented from obtaining this treatment.

Hypothalamic amenorrhea: from diagnosis to therapeutical approach

Among secondary amenorrheas, hypothalamic amenorrhea (HA) is the one with no evidence of endocrine/systemic causal factors. HA is mainly related to various stressors affecting neuroendocrine control of the reproductive axis. In clinical practice, HA is mainly associated with metabolic, physical, or psychological stress. Stress is the adaptive response of our body through all its homeostatic systems, to external and/or internal stimuli that activate specific and nonspecific physiological pathways. HA occurs generally after severe stressed conditions/situations such as dieting, heavy training, or intense emotional events, all situations that can induce amenorrhea with or without body weight loss and HA is a secondary amenorrhea with a diagnosis of exclusion. In fact, the diagnosis is essentially based on a good anamnestic investigation. It has to be investigated using the clinical history of the patient: occurrence of menarche, menstrual cyclicity, time and modality of amenorrhea, and it has to be excluded any endocrine disease or any metabolic (i.e., diabetes) and systemic disorders. It is necessary to identify any stressed situation induced by loss, family or working problems, weight loss or eating disorders, or physical training or agonist activity. Peculiar, though not specific, endocrine investigations might be proposed but no absolute parameter can be proposed since HA is greatly dependent from individual response to stressors and/or the adaptive response to stress. This chapter aims to give insights into diagnosis and putative therapeutic strategies.

The effects of opioids and opioid analogs on animal and human endocrine systems

Opioid abuse has increased in the last decade, primarily as a result of increased access to prescription opioids. Physicians are also increasingly administering opioid analgesics for noncancer chronic pain. Thus, knowledge of the long-term consequences of opioid use/abuse has important implications for fully evaluating the clinical usefulness of opioid medications. Many studies have examined the effect of opioids on the endocrine system; however, a systematic review of the endocrine actions of opioids in both humans and animals has, to our knowledge, not been published since 1984. Thus, we reviewed the literature on the effect of opioids on the endocrine system. We included both acute and chronic effects of opioids, with the majority of the studies done on the acute effects although chronic effects are more physiologically relevant. In humans and laboratory animals, opioids generally increase GH and prolactin and decrease LH, testosterone, estradiol, and oxytocin. In humans, opioids increase TSH, whereas in rodents, TSH is decreased. In both rodents and humans, the reports of effects of opioids on arginine vasopressin and ACTH are conflicting. Opioids act preferentially at different receptor sites leading to stimulatory or inhibitory effects on hormone release. Increasing opioid abuse primarily leads to hypogonadism but may also affect the secretion of other pituitary hormones. The potential consequences of hypogonadism include decreased libido and erectile dysfunction in men, oligomenorrhea or amenorrhea in women, and bone loss or infertility in both sexes. Opioids may increase or decrease food intake, depending on the type of opioid and the duration of action. Additionally, opioids may act through the sympathetic nervous system to cause hyperglycemia and impaired insulin secretion. In this review, recent information regarding endocrine disorders among opioid abusers is presented.

Diagnostic and therapeutic approach to hypothalamic amenorrhea

Hypothalamic amenorrhea (HA) is a secondary amenorrhea with no evidence of endocrine/systemic causal factors, mainly related to various stressors affecting neuroendocrine control of the reproductive axis. In clinical practice, HA is mainly associated with metabolic, physical, or psychological stress. Stress is the adaptive response of our body through all its homeostatic systems, to external and/or internal stimuli that activate specific and nonspecific physiological pathways. HA occurs generally after severe stress conditions/situations such as dieting, heavy training, or intense emotional events, all situations that can induce amenorrhea with or without body weight loss and HA is a secondary amenorrhea with a diagnosis of exclusion. In fact, the diagnosis is essentially based on a good anamnestic investigation. It has to be investigated using the clinical history of the patient: occurrence of menarche, menstrual cyclicity, time and modality of amenorrhea, and it has to be exclude any endocrine disease or any metabolic (i.e., diabetes) and systemic disorders. It is necessary to identify any stress situation induced by loss, family or working problems, weight loss or eating disorders, or physical training or agonist activity. Peculiar, though not specific, endocrine investigations might be proposed but no absolute parameter can be proposed since HA is greatly dependent from individual response to stressors and/or the adaptive response to stress. This article tries to give insights into diagnosis and putative therapeutic strategies.

High prevalence rate of pituitary incidentaloma: is it associated with the age-related decline of the sex hormones levels?

Incidental pituitary adenoma is the common finding during brain imaging. According to multistep model of pituitary tumourigenesis genetic alterations provide the initiating event that transforms cells while hormones play a role in promoting cell proliferation. Development of pituitary adenoma in a case of excessive hypophysiotrophic hormones production or reduced feedback suppression by target gland hormones emphasizes the importance of hormonal stimulation in pituitary tumourigenesis. Pituitary hyperplasia has been reported in pregnancy, hypothyroidism and conditions such as CRH or GHRH hypersecretion. Moreover, recent study reported one case of gonadotroph macroadenoma and two cases of gonadotroph cells hyperplasia in patients with Klinefelter syndrome probably due to protracted stimulation of gonadotroph cells because of lack of androgen feedback. Significant changes of the hypothalamic-pituitary-gonadal axis occurred with aging. In females, after menopause, estradiol level decreases by 35-fold and estrone level by 20-fold that results in increased gonadotropins levels. Similarly, FSH, but not LH, level is increased with advancing age in men, too, although the age-related difference in the level is less in comparison with women. Regarding these data, we hypothesised that high prevalence rate of pituitary incidentaloma in the elderly is associated with age-related decline in sex hormones levels and subsequent lack of feedback suppression leading to permanent gonadotrophs stimulation which is the crucial step in the pituitary tumour development. According to previously mentioned multistep model of pituitary tumourigenesis, incidentaloma will develop only in persons with already present intrinsic pituitary cell defects. However, further studies have to answer the questions of whether the incidence of pituitary tumours is more frequent in elderly, whether women with late onset menopause or those taking long-term hormone replacement therapy have lower rate of pituitary incidentaloma, and finally, is there any correlation between pituitary tumours incidence and serum concentrations of LH, FSH, bioavailable testosterone or estradiol.

The aging reproductive neuroendocrine axis

It is well known that the reproductive system is one of the first biological systems to show age-related decline. While depletion of ovarian follicles clearly relates to the end of reproductive function in females, evidence is accumulating that a hypothalamic defect is critical in the transition from cyclicity to acyclicity. This minireview attempts to present a concise review on aging of the female reproductive neuroendocrine axis and provide thought-provoking analysis and insights into potential future directions for this field. Evidence will be reviewed, which shows that a defect in pulsatile and surge gonadotropin hormone-releasing hormone (GnRH) secretion exists in normal cycling middle-aged female rats, which is thought to explain the significantly attenuated pulsatile and surge luteinizing hormone (LH) secretion at middle-age. Evidence is also presented, which supports the age-related defect in GnRH secretion as being due to a reduced activation of GnRH neurons. Along these lines, stimulation of GnRH secretion by the major excitatory transmitter glutamate is shown to be significantly attenuated in middle-aged proestrous rats. Corresponding age-related defects in other major excitatory regulatory factors, such as catecholamines, neuropeptide Y, and astrocytes, have also been demonstrated. Age-related changes in hypothalamic concentrations of neurotransmitter receptors, steroid receptors, and circulating steroid hormone levels are also reviewed, and discussion is presented on the complex interrelationships of the hypothalamus-pituitary-ovarian (HPO) axis during aging, with attention to how a defect in one level of the axis can induce defects in other levels, and thereby potentiate the dysfunction of the entire HPO axis.

Risk factors for hot flashes in midlife women

OBJECTIVE

To review the scientific literature pertaining to potential risk factors for hot flashes in midlife women.

METHODS

Scientific publications reporting on risk factors for hot flashes were identified through a systematic Medline search and are summarized in this review paper.

RESULTS

Although few studies have investigated risk factors for hot flashes in midlife women, consistent evidence suggests that smoking is associated with an increased risk for hot flashes. In addition, some studies suggest that other factors, such as hormone levels, body size, tubal ligation, surgical menopause, and race/ethnicity, may be associated with the occurrence of hot flashes.

CONCLUSIONS

Future studies are needed to confirm previous findings and to identify additional risk factors for hot flashes. Such studies will increase our understanding of the etiology of hot flashes and may lead to better treatments and preventive measures for this condition.

Hypogonadism in men consuming sustained-action oral opioids

Naturally occurring opiates (endorphins) diminish testosterone levels by inhibiting both hypothalamic gonadotrophin releasing hormone production and testicular testosterone synthesis. Heroin addicts treated with a single daily dose of methadone and nonaddicts receiving continuous intrathecal opioids quickly develop low luteinizing hormone and total testosterone levels. A similar pattern was sought in men consuming commonly prescribed oral opioids. Free testosterone (FT), total testosterone (TT), estradiol (E(2)), dihydrotestosterone (DHT), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) were measured in 54 community-dwelling outpatient men consuming oral sustained-action dosage forms of opioids several times daily for control of nonmalignant pain. Hormone levels were related to the opioid consumed, dosage and dosage form, nonopioid medication use, and several personal characteristics and were compared with the hormone analyses of 27 similar men consuming no opioids. Hormone levels averaged much lower in opioid users than in control subjects in a dose-related pattern (P < .0001 for all comparisons). FT, TT, and E(2) levels were subnormal in 56%, 74%, and 74%, respectively, of opioid consumers. Forty-eight men (89%) exhibited subnormal levels of either FT or E(2). Either TT or E(2) level was subnormal in all 28 men consuming the equivalent of 100 mg of methadone daily and in 19 of 26 (73%) consuming smaller opioid doses. Eighty-seven percent (39 of 45) of opioid-ingesting men who reported normal erectile function before opioid use reported severe erectile dysfunction or diminished libido after beginning their opioid therapy. Commonly prescribed opioids in sustained-action dosage forms usually produce subnormal sex hormone levels, which may contribute to a diminished quality of life for many patients with painful chronic illness.

Pivagabine decreases stress-related hormone secretion in women with hypothalamic amenorrhea

Stress-induced neuroendocrine activities influence the regulation of endocrine glands and axes. Weight loss-related hypothalamic amenorrhea is a typical stress-induced physiopathological condition. It is characterized by increased adrenal cortex activation and by reduced GH, LH, FSH and gonadal steroid hormone levels. The aim of the present study was to investigate the effects of pivagabine, a neurotropic drug (1800 mg/day for 7 days) or placebo administration on ACTH, cortisol, GH, LH, FSH and PRL plasma levels in patients with hypothalamic amenorrhea related to weight loss. Hormonal parameters and the pulsatile release of cortisol (6-hour pulsatility, sampling every 10 minutes) were evaluated before and after 7 days of treatment. Pivagabine administration significantly reduced mean plasma ACTH (from 21.7+/-1.7 to 15.4+/-1.2 pg/ml, p<0.05) and cortisol levels (from 12.2+/-0.7 to 9.7+/-0.7 ng/ml, p<0.05) and increased GH levels (from 1.4+/-0.5 to 3.0+/-0.9 ng/ml, p<0.05). A significant reduction of cortisol pulse amplitude was observed (p<0.01) while no change in pulse frequency occurred. No changes were observed in placebo-treated subjects. LH, FSH and PRL levels were not modified by placebo or pivagabine administration. In conclusion, in patients with hypothalamic amenorrhea related to weight loss pivagabine induced a significant decrease of cortisol secretion and an increase of GH release by pivagabine administration, suggesting that this drug exerts a specific neuroendocrine modulatory role.

Older men manifest multifold synchrony disruption of reproductive neurohormone outflow

Under a working clinical hypothesis that aging putatively disrupts neuroendocrine control mechanisms, here we test a specific corollary notion that transitions in sleep stage, oscillations in nocturnal penile tumescence (NPT; a neurogenically organized signal), and the rates of instantaneous secretion of LH and/or testosterone are jointly synchronous in healthy young, but not older, men. To this end, we evaluated 10 young (aged 21-31 yr) and 8 older (aged 65-74 yr) men by intensive overnight multisite monitoring, viz. simultaneous electro-encephalogram and NPT recordings (every 30 s) and remote blood sampling (every 2.5 min) to quantitate LH and testosterone release. Waveform-independent deconvolution and cross-correlation analyses of these neurohormone outflow measures revealed that healthy young men sustain four salient physiological linkages overnight: 1) a strong inverse (confirmatory) relationship between sleep stage and NPT activity, such that deeper sleep is accompanied by suppression of NPT; 2) consistent coupling between NPT and testosterone secretion, wherein heightened NPT activity respectively precedes and follows increased testosterone secretion by 12.5-32.5 and 50-60 min; 3) evident synchrony between sleep stage and testosterone secretion, in which testosterone secretion increases over a 30-min window (-2.5 to 25 min) while sleep deepens; and 4) a close temporal linkage between instantaneous LH release and NPT oscillations, whereby LH secretion increases 55-62.5 min before and again 5-30 min after NPT declines. In contrast, older men manifested global loss of expected young adult synchrony; namely, 1) abolition of the inverse relationship between sleep stage and NPT, 2) decorrelation of NPT oscillations and testosterone secretion, 3) decoupling of testosterone release and deep sleep, and 4) abrogation of the linkage between LH secretion and penile detumescence. In summary, high intensity overnight monitoring of multiple reproductive neuroendocrine outflow measures simultaneously in young men delineates prominent neurophysiological coupling among sleep transitions and NPT activity, LH and testosterone secretion or NPT oscillations, and testosterone secretion and deepening sleep stage. In contrast, healthy older men exhibit near-universal disruption of physiological young adult synchronicity. Thus, we conclude that male reproductive aging is marked by erosion of coordinate regulation among sleep transitions, central nervous system-directed NPT activity, and hypothalamically driven episodic GnRH/LH (and thereby Leydig cell testosterone) secretion. Whether analogous multifold uncoupling of neurohormone signals emerges in the course of reproductive aging in women or in nonhuman species is not yet known.

Few oligo-amenorrheic athletes have vasomotor symptoms

OBJECTIVE

To assess whether women with athletic oligo-amenorrhea have vasomotor symptoms.

MATERIAL AND METHODS

A mailed questionnaire was sent to 252 female athletes about vasomotor symptoms. Identical questions were also mailed to 1523 peri- and postmenopausal women.

RESULTS

The prevalence of vasomotor symptoms was low in female athletes with oligo- and amenorrhea and similar to that found in athletes with regular menstruations. The prevalence was significantly lower than in menopausal women. Although more than a third of the menopausal women had hormone replacement therapy, 30% of them still had vasomotor symptoms at least every week compared with only 2% of the oligo-amenorrheic athletes.

CONCLUSION

Vasomotor symptoms are very uncommon in oligo-amenorrheic athletes, although many of them are hypoestrogenic. It was suggested that one factor contributing to these symptoms around menopause is low hypothalamic activity of beta-endorphins, which makes the thermoregulatory centre labile. On the other hand, supraphysiological activity in hypothalamic beta-endorphins may cause the oligo-amenorrhea in athletes, but may stabilise the thermoregulatory centre and thus prevent hot flushes.

The effect of estrogens and antiestrogens in a rat model for hot flush

The present studies evaluated the effect of estrogens and the selective estrogen receptor modulator (SERM) tamoxifen and raloxifene in a rat model for hot flush. In this model, ovariectomized rats were treated for 8 or 9 days either sc or po. Rats were dependent to morphine by implanting a morphine pellet (75 mg each) sc on days 3 and 5 of treatment. On the last day of treatment, a thermistor, connected to a data acquisition system, was placed on the tail of each animal and morphine addiction was withdrawn by naloxone injection (1.0 mg/kg, sc). Temperature measurements were taken for 1 h under ketamine (80 mg/kg, im) anesthesia. In general, vehicle treated rats showed a 5-6 degrees C elevation of their tail skin temperature with the peak occurring about 15 min after naloxone injection. 17 alpha-Ethinyl estradiol (EE) was evaluated both sc and po using a broad range of doses. The IC50 for inhibition of tail skin temperature rise was approximately 0.1 mg/kg, sc and 0.2 mg/kg, po. 17 beta-Estradiol and 17 alpha-estradiol were also active in this model whereas non-estrogenic steroids were inactive. Raloxifene and tamoxifen were tested for estrogen agonist and antagonist activity administered sc and po. Raloxifene did not demonstrate reproducible estrogen agonist activity at doses up to 10 mg/kg, whereas it demonstrated significant antagonistic activity at the 10 mg/kg dose regardless of the route of administration. Tamoxifen exhibited significant estrogen agonist activity at all doses tested (0.1-10.0 mg/kg) and was a significant antagonist of EE at the 1.0 mg/kg dose. Our results demonstrate the potential utility of this model to evaluate and discriminate among classes of compounds with varying degrees of estrogen agonist and antagonist activity.

Physical exercise and vasomotor symptoms in postmenopausal women

BACKGROUND

The mechanisms causing postmenopausal vasomotor symptoms are unknown, but changes in hypothalamic beta-endorphins have been suggested to be involved. beta-endorphin production may be increased by regular physical exercise.

OBJECTIVE

To assess if physically active women suffered from vasomotor symptoms to a lower extent than sedentary women.

MATERIAL AND METHODS

All women (n = 1323) in the ages ranging from 55-56 years in the community of Linköping Sweden, were included. In a questionnaire these women were asked about their physical exercise habits and their complaints from vasomotor symptoms. Only those 793 women who had reached a natural menopause were grouped into sedentary, moderately or highly active women, based on a physical activity score.

RESULTS

Only 5% of highly physically active women experienced severe hot flushes as compared with 14-16% of women who had little or no weekly exercise (P < 0.05; relative risk 0.26; CI 95%: 0.10-0.71). This was not explained by differences in body mass index, smoking habits or use of hormone replacement therapy. Women who used hormone replacement therapy were more physically active than non-users (P < 0.05).

CONCLUSION

Fewer physically active women had severe vasomotor symptoms compared with sedentary women. This may be due to a selection bias but also to the fact that physical exercise on a regular basis affects neurotransmitters which regulate central thermoregulation.

Ontogeny of the circadian rhythm in medial basal hypothalamic beta-endorphin content in female rat

The present study evaluated the possible role of estrogens in generating the circadian rhythm of medial basal hypothalamus content at the time of puberty in female rats. Accordingly, changes in medial basal hypothalamus beta-endorphin (beta-EP) content were investigated in female rats, before and at puberty. Groups of intact or ovariectomized rats were studied after estradiol-benzoate or placebo treatment. The results showed that circadian rhythm of beta-EP content of medial basal hypothalamus is absent in prepubertal rats, while it appears at puberty, associated to a significant increase of beta-EP concentration. The primary involvement of steroids in generating this circadian rhythm was supported by the finding that estradiol-benzoate treatment caused a precocious appearance of beta-EP hypothalamic diurnal changes in prepubertal rats. Moreover, estradiol-benzoate replacement restored the loss of beta-EP nocturnal increase induced by ovariectomy in pubertal animals. Therefore, these data support the significant role of estrogen in inducing the circadian rhythm of beta-EP content in medial basal hypothalamus at the time of puberty in female rats.

Altered sexual function and decreased testosterone in patients receiving intraspinal opioids

Altered sexual function has been reported in individuals addicted to opioids or on methadone maintenance, yet little literature is available regarding the effect of intraspinal opioids on libido or sex hormone levels. We evaluated sexual function and plasma sex hormone levels in six men treated with chronic intraspinal opioids. All patients had some reduction in libido and four patients had difficulty obtaining or maintaining an erection. These changes were noted within 1 month of beginning intraspinal opioid therapy. Serum testosterone levels ranged from 26 to 367 ng/dL (normal, 350-1500 ng/dL); the mean serum level was 197.7 ng/dL (SD = 119.8). Serum testosterone levels and other sex hormones, including follicle-stimulating hormone, luteinizing hormone, sex-hormone-binding globulin, and prolactin, should be measured prior to and at various points during intraspinal opioid therapy. Patients should be queried regarding sexual function and should be cautioned regarding the possibility of these adverse effects prior to initiating spinal opioids. Supplemental testosterone should be considered to treat this dysfunction.

Effects of ovariectomy, gonadal steroid replacement and photoperiod on plasma β-endorphin in the ewe

The effects of gonadectomy, photoperiod and ovarian steroid replacement on plasma beta-endorphin concentrations were studied in 2 experiments using mature ewes. In Experiment 1 ovariectomy resulted in an increased plasma beta-endorphin concentration. Changing the photoperiod from long to short daylength had little effect on beta-endorphin, but transfer from short to long photoperiod caused a fall in the beta-endorphin level. In Experiment 2 ovariectomy again caused an increase in plasma beta-endorphin. Treatment with progesterone, estradiol or a combination of both failed to reduce the level to preovariectomy values, although LH concentrations were reduced. No diurnal rhythmicity in beta-endorphin secretion was observed.

Effects of ovarian surgery on the dopaminergic and opioidergic control of gonadotropin and prolactin secretion in women with polycystic ovarian disease

Ovarian surgery has been demonstrated as an effective means to establish regular menstrual cycles and resumption of ovulation in patients with polycystic ovarian disease (PCO). We questioned whether such reinstitution of menstrual cyclicity may be associated with changes in the opioidergic and dopaminergic activity known to be aberrant in these women. Opioidergic and dopaminergic tone was therefore assessed in patients with PCO before and after ovarian laser vaporization (n = 4) or classical ovarian wedge resection (n = 4). Blood samples for the determination of luteinizing hormone (LH), follicle stimulating hormone (FSH) and prolactin were frequently obtained following opioidergic and/or dopaminergic antagonism affected by naloxone (4 mg i.v.) or metoclopramide (10 mg i.v.). In response to either surgical approach, circulating LH levels decreased (p < 0.01), while FSH concentrations remained unaltered. Further, LH and FSH concentrations did not noticeably change following challenges with naloxone or metoclopramide: this applied to conditions before and after ovarian surgery. Prolactin release in response to metoclopramide was markedly (p < 0.01) higher following ovarian surgery than before. Thus, both ovarian laser surgery and classical wedge resection can effectively restore normal menstrual cyclicity in PCO patients, although they failed to alter opioidergic and dopaminergic activity. Dopaminergic inhibition of prolactin secretion was further enhanced after ovarian surgery. These observations suggest that different modes of ovarian surgery are effective in influencing central gonadal control, but that the central opioidergic and dopaminergic control of gonadotropin and prolactin secretion remains unaffected by ovarian surgery in PCO women, even when menstrual cyclicity is resumed.

The brain as a target organ of gonadal steroids

Gonadal steroids have many effects in the central nervous system. Through a feedback mechanism, they influence the synthesis and release of hypothalamic gonadotropin-releasing hormone (GnRH) and/or pituitary gonadotropic hormones (luteinizing hormone, LH, and follicle stimulating hormone, FSH). Endogenous opioid peptides (EOPs) represent one of the key factors modulating the activity of sex steroids on the hypothalamus-pituitary-gonadal (HPG) axis. In particular, these peptides control the secretion of LH by inhibiting the activity of the hypothalamic neurons which produce GnRH. The EOP effect is dependent on the steroid hormone milieu, as shown by different responses to naloxone administration, both in animals and in humans. For the naloxone-induced increase in LH secretion to occur, relatively high levels of sex steroids are required. In humans, LH release is absent before sexual maturation. In fertile women, naloxone administration increases LH levels in the luteal phase but not in the follicular phase. In the postmenopausal period, naloxone has no effect on LH release; estrogen/progestin therapy does restore the LH response.

Relationship between cerebrospinal fluid beta-endorphin and plasma pituitary-gonadal hormone levels in women

Brain beta-endorphin (beta-EP) plays an important role in regulating the hypothalamus-pituitary-gonadal axis activity. Cerebrospinal fluid (CSF) beta-EP levels seem to reflect the central rather than pituitary secretion. With the aim to correlate the changes of plasma estradiol (E2), progesterone, luteinizing hormone (LH) and follicle-stimulating hormone with brain beta-EP, CSF levels of beta-EP were measured in 15 normally cycling and 15 postmenopausal women. CSF beta-EP levels in post-menopausal women were lower than in fertile women. A positive correlation between plasma E2 and CSF beta-EP level was found in all women. In fertile women CSF beta-EP levels were inversely correlated to plasma gonadotropin levels. These results showed that CSF beta-EP levels differ between fertile and postmenopausal women and are correlated with plasma LH and E2, suggesting a strong linkage between central beta-EP levels and pituitary-gonadal axis hormones.

Effect of pulsatile luteinizing hormone-releasing hormone administration on pituitary-gonadal function in elderly man

The effect of short-term pulsatile LHRH administration was studied in 8 healthy subjects ranging from 60 to 81 yr to see if the decrease of pituitary gonadal function could be in part due to changes in the discharge of LHRH from the hypothalamus. Gonadotropin and testosterone (T) secretion was evaluated two weeks before and during LHRH (122-160 ng/kg bw every 120 min sc) infusion. In addition, a bolus dosage of LHRH (50 mu iv) was given both at the beginning and at the end of pulsatile LHRH administration in order to test gonadotrophs sensitivity. A significant increase in gonadotropin levels from day 0 to day 4 was found, and was followed by a subsequent decrease from day 7 to day 14. A slight significant increase in T levels was observed during LHRH administration (p less than 0.01). LH pulses were identified in 5 out of 8 subjects on day 0. On day 14, all the exogenous LHRH pulses were followed by significant LH bursts. There was not a significant decrease in the pituitary LH responsiveness to LHRH test from day 0 to day 14. Our study seems to indicate that pituitary - gonadal unit in normal elderly men can be modulated by pulsatile administration of LHRH. A pulse frequency of LHRH which is probably similar to the physiological one, could induce a slight increase in T levels via qualitative changes in LH activity. We can assume that clinical changes in gonadal activity might also be connected to some disturbances in endogenous LHRH pulsar.

Opioid control of luteinizing hormone secretion in humans

The observation that heroin-addicted subjects are amenorrheic and/or hypogonadic suggested a possible role of endogenous opioid peptides (EOP) in the regulation of the hypothalamus-pituitary-gonodal axis. Because EOP are localized all through the axis, they may influence the reproductive function acting at various levels. The injection of morphine decreases plasma LH levels, abolishing the pulsatile pattern of secretion. The evidence that naloxone, an opiate receptor blockade, increases LH levels suggests a tonic inhibitory action of EOP. The naloxone-induced LH increase is not observed before pubertal maturation, in both sexes, and is absent in children with delayed or precocious puberty and in those with Klinefelter's or Turner's syndrome, suggesting a role of gonadal function on the opioid control of LH secretion. In adult women this LH response to naloxone is present during the periovulatory and the luteal phase of the menstrual cycle, suggesting a permissive role of estradiol and mainly of progesterone on the action of EOP on the LH secretion. Indeed, in amenorrheic subjects naloxone lacks to stimulate plasma LH levels and the treatment for the induction of ovulation restores this activity. An increased inhibitory action of EOP on GnRH release may explain the inefficacy of naloxone to stimulate LH secretion in hypogonadotropinic patients, while a decreased action has been hypothesized in postmenopausal women. The clinical implications of EOP in reproductive medicine appear to be promising.

Effect of oral contraceptives or dexamethasone on plasma beta-endorphin during the menstrual cycle

Several studies have showed a significant increase of plasma beta-endorphin levels during the periovulatory days of the menstrual cycle. The aim of the present study was to investigate the origin of the periovulatory changes of plasma beta-endorphin, trying to discriminate between a possible ovarian and/or pituitary origin. Daily plasma beta-endorphin, luteinizing hormone (LH), and cortisol levels were measured from the 8th to the 20th day of the menstrual cycle in healthy normal-cycling women (10 cases) before and during dexamethasone (DEX; 6 cases) or estroprogestinic treatment with monophasic (5 cases) or triphasic (5 cases) pill. In the control menstrual cycle, during the preovulatory days, a significant increase of plasma beta-endorphin was found. While oral contraceptives abolished the midcycle increase of plasma beta-endorphin, the periovulatory plasma beta-endorphin peak was present during DEX treatment. Plasma cortisol levels did not show any significant change throughout the control menstrual cycle, while they were significantly lowered by the DEX administration and significantly increased during estroprogestinic treatment. These results suggest that the increase of plasma beta-endorphin during the periovulatory days is related to the ovulatory function, and suggest a possible ovarian origin.

Effects of ovariectomy and estradiol replacement on naloxone induced LH secretion in the female rabbit

The effects of an opioid antagonist, naloxone, on the secretion of gonadotrophins were investigated in the long term ovariectomized rabbit. In the intact and acutely ovariectomized rabbit (2 days p.o.) naloxone at 10 mg/kg induced an increase of 260-300% in LH secretion at 40 min post-injection. From days 33-66 post-surgery naloxone at 10 mg/kg caused significant elevations in LH release even when animals were treated with estradiol benzoate 24 h previously. By contrast, treatment with oestradiol benzoate 3 h before naloxone abolished the LH increase. An LH surge could be elicited in these rabbits with GnRH treatment. These studies indicated that long term ovariectomy in the female rabbit does not completely remove the opioid control of GnRH release and that the LH response to naloxone is influenced by circulating estradiol levels.

Effect of morphine on hCG release by first trimester human trophoblast in vitro

Opiate synthesis by human placental cells and the presence of kappa-type opiate binding sites in the syncytiotrophoblast brush border membrane may indicate the possible role of morphine-like substances in the autocrine regulation of trophoblast cell metabolism. This study was undertaken to examine the in vitro effect of morphine on hCG (human chorionic gonadotrophin) and hPL (human placental lactogen) release by 1st and 3rd trimester placental tissue explants. The results have shown that morphine (100 nM) significantly stimulated hCG secretion by 6-8 weeks old trophoblast and was without effect on hPL. Hormone secretion by term placental tissue explants was unaffected by morphine treatment. Based on these results we assume that opiates may have a role in the local (autocrine and/or paracrine) regulation of hCG secretion in early gestation.

Adrenal steroid responses to naloxone in polycystic ovarian disease

In order to investigate the role of the adrenal gland in the pathogenesis of polycystic ovarian disease (PCOD), we evaluated the adrenal steroid response to an opiate receptor blockade. Six healthy menstruating volunteers and 6 patients with PCOD were given a saline or naloxone (4 mg i.v.) injection in the early follicular phase. Blood samples were taken prior to the injections and every 15-30 minutes in the following 2 hours. Cortisol, androstenedione (A) and dehydroepiandrosterone (DHA) plasma levels were determined by RIA after extraction (cortisol) and celite chromatography (A and DHA). While in controls naloxone increased only cortisol concentrations, in PCOD patients DHA plasma levels also were stimulated by the opiate receptor antagonist. In PCOD patients the increase of cortisol (p less than 0.05) and of DHA (p less than 0.001) levels resulted significantly higher than in controls. In both groups A plasma levels remained unchanged after naloxone administration. These data confirm that endogenous opioids exert an inhibitory control on the pituitary-adrenal axis. In PCOD patients the response to naloxone led to a hypersecretion of adrenal delta 5-androgens, which could account for the development of the syndrome.

Opioid regulation of luteinizing hormone in amenorrheic patients after therapy for induction of ovulation

This study evaluated the activity of central opiate receptors modulating luteinizing hormone (LH) secretion before and during treatment with human menopausal gonadotropin (n = 8) or purified human urinary follicle-stimulating hormone (n = 6) in 14 patients with hypogonadotropic hypogonadism (n = 6) or secondary amenorrhea (n = 8). LH response to saline infusion and naloxone administration (4 mg intravenously) was assessed. As control, 6 normal ovulating women were studied. Before therapy, all amenorrheic patients showed no LH increase after naloxone injection. Gonadotropin treatment restored the naloxone-induced LH response at preovulatory and midluteal phases in ovulating patients with secondary amenorrhea. The same response was present in spontaneously ovulating women but was absent in the hypogonadotropic hypogonad patients, despite the gonadotropin therapy's efficiency. In conclusion, when the alteration of gonadotropin-releasing hormone synthesis and/or release is reversible, the opioid system actively participates in the regulation of the hypothalamus-pituitary-gonadal axis.

Progesterone and progestins modulate beta-endorphin concentrations in the hypothalamus and in the pituitary of castrated female rats

Hypothalamic and pituitary beta-endorphin (B-EP) concentrations are modified by ovariectomy and estrogen treatments, supporting a direct interaction between this peptidergic system and gonadal steroids. Because the use of progestins is becoming even more diffuse in clinical practice, we evaluated the effect of progesterone and of the synthetic progestins medroxyprogesterone acetate (MPA), norethisterone acetate (NET) and desogestrel on the concentration of B-EP in the medial-basal hypothalamus and the anterior and neurointermediate pituitary lobes in ovariectomized rats (OVX), treated or untreated with estradiol benzoate (EB). B-EP concentrations were significantly increased by desogestrel in the anterior lobe and by progesterone, desogestrel and medroxyprogesterone acetate in the neurointermediate lobe. Progesterone and progestins significantly reduced B-EP increase induced by estradiol benzoate in the anterior lobe. Estradiol benzoate treatment did not modify the effect of progesterone and desogestrel on B-EP in the neuro-intermediate pituitary lobe. Norethisterone acetate and progesterone increased B-EP concentrations in the medial-basal hypothalamus, while the other steroids were inactive. In contrast, in the hypothalamus all progestins attenuated the increase of B-EP induced by estradiol benzoate (p less than 0.01). These data indicate that progesterone and progestins modulate the hypothalamic and pituitary B-EP concentrations in concert with estrogens. The capacity of progestins to modify the hypothalamic contents of B-EP may represent one of the mechanisms of action of these steroids in influencing brain function.