Long-term melatonin administration does not alter pituitary-gonadal hormone secretion in normal men

My voyage in the enchanted world of sleep

In this paper, I describe my 45-year career in sleep research. I started my undergraduate studies at Tel Aviv University, where I was first introduced to the enchanted world of sleep, continued to my graduate studies with Wilse B. Webb at the University of Florida, and then to post-doctoral training with Dan Kripke at the University of California at San Diego. Then, I describe the evolution of my academic career at the Technion-Israel Institute of Technology, where I started in 1975 as an Assistant Professor and retired in 2019 as the President of the Institute. I describe the areas of research that I pursued and how the research developed, emphasizing unexpected results that guided me and my lab team in new directions. This includes my early studies on ultradian rhythms, inspired by Nathaniel Kleitman's Basic Rest Activity Cyle hypothesis, utilizing the ultrashort sleep-wake paradigm to chart the 24-hour sleep propensity function, and how these studies led us to explore the role of melatonin in sleep regulation. I also explain why we directed our attention to sleep apnea, and how clinical observations led to the provocative hypothesis that sleep apnea-typically seen as a disorder-may also play a protective role. Under the leadership of my research partner and wife, Lena, we confirmed this hypothesis. Also in this article, I describe my enthusiasm for the history of our field and, as derived from my experience as a Dean of Medicine and President of a university, I share my philosophy about the role of members of academia in society. I emphasize that none of my achievements could have been accomplished without the hard work and motivation of my students and research partners, who shared my enthusiasm and passion for the enchanted world of sleep. This paper is part of the Living Legends in Sleep Research series, which is sponsored by Idorsia Pharmaceuticals and Jazz Pharmaceuticals.

Protective effects of exogenous melatonin therapy against oxidative stress to male reproductive tissue caused by anti-cancer chemical and radiation therapy: a systematic review and meta-analysis of animal studies

Background

Male testicular dysfunction is a considerable complication of anti-cancer therapies, including chemotherapy and radiotherapy, partly due to the increased oxidative stress caused by these treatments. Melatonin is an effective antioxidant agent that protects testicles against physical and toxic chemical stressors in animal models. This study aims to systematically review the melatonin's protective effects against anti-cancer stressors on rodential testicular tissue.

Materials and Method

An extensive search was conducted in Web of Science, Scopus, and PubMed for animal studies investigating exogenous melatonin's protective effects on rodent testicles exposed to anti-cancer chemicals and radiotherapeutic agents. Using the DerSimonian and Laird random-effect model, standardized mean differences and 95% confidence intervals were estimated from the pooled data. The protocol was prospectively registered in the International Prospective Register of Systematic Reviews (PROSPERO: CRD42022355293).

Results

The meta-analysis included 38 studies from 43 studies that were eligible for the review. Rats and mice were exposed to radiotherapy (ionizing radiations such as gamma- and roentgen radiation and radioactive iodine) or chemotherapy (methotrexate, paclitaxel, busulfan, cisplatin, doxorubicin, vinblastine, bleomycin, cyclophosphamide, etoposide, Taxol, procarbazine, docetaxel, and chlorambucil). According to our meta-analysis, all outcomes were significantly improved by melatonin therapy, including sperm quantity and quality (count, motility, viability, normal morphology, number of spermatogonia, Johnsen's testicular biopsy score, seminiferous tubular diameter, and seminiferous epithelial height), serum level of reproductive hormones (Follicle-Stimulating Hormone and testosterone), tissue markers of oxidative stress (testicular tissue malondialdehyde, superoxide dismutase, glutathione peroxidase, catalase, glutathione, caspase-3, and total antioxidant capacity), and weight-related characteristics (absolute body, epididymis, testis, and relative testis to body weights). Most SYRCLE domains exhibited a high risk of bias in the included studies. Also, significant heterogeneity and small-study effects were detected.

Conclusion

In male rodents, melatonin therapy was related to improved testicular histopathology, reproductive hormones, testis and body weights, and reduced levels of oxidative markers in testicular tissues of male rodents. Future meticulous studies are recommended to provide a robust scientific backbone for human applications.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022355293, identifier CRD42022355293.

Gut Bless Your Pain—Roles of the Gut Microbiota, Sleep, and Melatonin in Chronic Orofacial Pain and Depression

Background. Increased attention has been paid to the gut–brain axis recently, but little is known so far regarding how this translates into pain susceptibility. Aim. The aim of this review is to determine whether gastroenterological disorders and sleep disorders (directly or indirectly) contribute to an increased susceptibility to depression and chronic orofacial pain. Method. A search was performed in the U.S. National Library of Medicine (PubMed) database in order to find studies published before 19 December 2021. We used the following terms: gut microbiome, OR sleep quality, OR melatonin, OR GERD, OR IBS, AND: depression OR chronic pain, in different configurations. Only papers in English were selected. Given the large number of papers retrieved in the search, their findings were described and organized narratively. Results. A link exists between sleep disorders and gastroenterological disorders, which, by adversely affecting the psyche and increasing inflammation, disturb the metabolism of tryptophan and cause excessive microglial activation, leading to increased susceptibility to pain sensation and depression. Conclusions. Pain therapists should pay close attention to sleep and gastrointestinal disorders in patients with chronic pain and depression.

What do we really know about the safety and efficacy of melatonin for sleep disorders?

Melatonin is a hormonal product of the pineal gland, a fact that is often forgotten. Instead it is promoted as a dietary supplement that will overcome insomnia, as an antioxidant and as a prescription only drug in most countries outside the United States of America and Canada. The aim of this review is to step back and highlight what we know about melatonin following its discovery 60 years ago. What is the role of endogenous melatonin; what does melatonin do to sleep, body temperature, circadian rhythms, the cardiovascular system, reproductive system, endocrine system and metabolism when administered to healthy subjects? When used as a drug/dietary supplement, what safety studies have been conducted? Can we really say melatonin is safe when it has not been systematically studied and many studies show interactions with a wide range of physiological processes? Finally the results of studies investigating the efficacy of melatonin as a drug to alleviate insomnia are critically evaluated. In summary, melatonin is an endogenous pineal gland hormone with specific physiological functions in animals and humans, with its primary role in humans to maintain synchrony of sleep with the day/night cycle. When administered as a drug it affects a wide range of physiological systems and has clinically important drug interactions. With respect to efficacy for treating sleep disorders, melatonin can advance the time of sleep onset but the effect is modest and variable. In children with neurodevelopmental disabilities melatonin appears to have the greatest impact on sleep onset but little effect on sleep efficiency.

The Crosstalk between Melatonin and Sex Steroid Hormones

Melatonin, an indolamine mainly released from the pineal gland, is associated with many biological functions, namely, the modulation of circadian and seasonal rhythms, sleep inducer, regulator of energy metabolism, antioxidant, and anticarcinogenic. Although several pieces of evidence also recognize the influence of melatonin in the reproductive physiology, the crosstalk between melatonin and sex hormones is not clear. Here, we review the effects of sex differences in the circulating levels of melatonin and update the current knowledge on the link between sex hormones and melatonin. Furthermore, we explore the effects of melatonin on gonadal steroidogenesis and hormonal control in females. The literature review shows that despite the strong evidence that sex differences impact on the circadian profiles of melatonin, reports are still considerably ambiguous, and these differences may arise from several factors, like the use of contraceptive pills, hormonal status, and sleep deprivation. Furthermore, there has been an inconclusive debate about the characteristics of the reciprocal relationship between melatonin and reproductive hormones. In this regard, there is evidence for the role of melatonin in gonadal steroidogenesis brought about by research that shows that melatonin affects multiple transduction pathways that modulate Sertoli cell physiology and consequently spermatogenesis, and also estrogen and progesterone production. From the outcome of our research, it is possible to conclude that understanding the correlation between melatonin and reproductive hormones is crucial for the correction of several complications occurring during pregnancy, like preeclampsia, and for the control of climacteric symptoms.

Optogenetic sleep enhancement improves fear-associated memory processing following trauma exposure in rats

Sleep disturbances are commonly found in trauma-exposed populations. Additionally, trauma exposure results in fear-associated memory impairments. Given the interactions of sleep with learning and memory, we hypothesized that increasing sleep duration following trauma exposure would restore overall function and improve trauma-induced fear-associated memory dysfunction. Here, we utilized single prolonged stress, a validated rodent model of post-traumatic stress disorder, in combination with optogenetic activation of hypothalamic melanin-concentrating hormone containing cells to increase sleep duration. The goal of this work was to ascertain if post-trauma sleep increases are sufficient to improve fear-associated memory function. In our laboratory, optogenetic stimulation after trauma exposure was sufficient to increase REM sleep duration during both the Light and Dark Phase, whereas NREM sleep duration was only increased during the Dark Phase of the circadian day. Interestingly though, animals that received optogenetic stimulation showed significantly improved fear-associated memory processing compared to non-stimulated controls. These results suggest that sleep therapeutics immediately following trauma exposure may be beneficial and that post-trauma sleep needs to be further examined in the context of the development of post-traumatic stress disorder.

Adverse Events Associated with Melatonin for the Treatment of Primary or Secondary Sleep Disorders: A Systematic Review

BACKGROUND

Melatonin is widely available either on prescription for the treatment of sleep disorders or as an over-the-counter dietary supplement. Melatonin has also recently been licensed in the UK for the short-term treatment of jetlag. Little is known about the potential for adverse events (AEs), in particular AEs resulting from long-term use. Concern has been raised over the possible risks of exposure in certain populations including pre-adolescent children and patients with epilepsy or asthma.

OBJECTIVES

The aim of this systematic review was to assess the evidence for AEs associated with short-term and longer-term melatonin treatment for sleep disorders.

METHODS

A literature search of the PubMed/Medline database and Google Scholar was conducted to identify randomised, placebo-controlled trials (RCTs) of exogenous melatonin administered for primary or secondary sleep disorders. Studies were included if they reported on both the types and frequencies of AEs. Studies of pre-term infants, studies of < 1 week in duration or involving single doses of melatonin and studies in languages other than English were excluded. Findings from open-label studies that raised concerns relating to AE reports in patients were also examined. Studies were assessed for quality of reporting against the Consolidated Standards of Reporting Trials (CONSORT) checklist and for risk of bias against the Cochrane Collaboration risk-of-bias criteria.

RESULTS

37 RCTs met criteria for inclusion. Daily melatonin doses ranged from 0.15 mg to 12 mg. Subjects were monitored for up to 29 weeks, but most studies were of much shorter duration (4 weeks or less). The most frequently reported AEs were daytime sleepiness (1.66%), headache (0.74%), other sleep-related AEs (0.74%), dizziness (0.74%) and hypothermia (0.62%). Very few AEs considered to be serious or of clinical significance were reported. These included agitation, fatigue, mood swings, nightmares, skin irritation and palpitations. Most AEs either resolved spontaneously within a few days with no adjustment in melatonin, or immediately upon withdrawal of treatment. Melatonin was generally regarded as safe and well tolerated. Many studies predated publication of the CONSORT checklist and consequently did not conform closely to the guidelines. Similarly, only eight studies were judged 'good' overall with respect to the Cochrane risk-of-bias criteria. Of the remaining papers, 16 were considered 'fair' and 13 'poor' but publication of almost half of the papers preceded that of the earliest version of the guidelines.

CONCLUSION

Few, generally mild to moderate, AEs were associated with exogenous melatonin. No AEs that were life threatening or of major clinical significance were identified. The scarcity of evidence from long-term RCTs, however, limits the conclusions regarding the safety of continuous melatonin therapy over extended periods. There are insufficient robust data to allow a meaningful appraisal of concerns that melatonin may result in more clinically significant adverse effects in potentially at-risk populations. Future studies should be designed to comply with appropriate quality standards for RCTs, which most past studies have not.

Seasonal Changes of Serum Gonadotropins and Testosterone in Men Revealed by a Large Data Set of Real-World Observations Over Nine Years

Environmental rhythmicity is able to affect the hypothalamic-pituitary-gonadal axis in several animals to achieve reproductive advantages. However, conflicting results were obtained when assessing the environmental-dependent rhythmicity on reproductive hormone secretion in humans. This study was designed to evaluate seasonal fluctuations of the main hormones involved in the hypothalamic-pituitary-gonadal axis in men, using a big data approach. An observational, retrospective, big data trial was carried out, including all testosterone, luteinizing hormone (LH) and follicle-stimulating hormone (FSH) measurements performed in a single laboratory between January 2010 and January 2019 using Chemiluminescent Microparticle Immunoassay. Subjects presenting any factor interfering with the hypothalamic-pituitary-gonadal axis were excluded. The trend and seasonal distributions were analyzed using autoregressive integrated moving average (ARIMA) models. A total of 12,033 data, accounting for 7,491 men (mean age 47.46 ± 13.51 years, range 18-91 years) were included. Testosterone serum levels (mean 5.34 ± 2.06 ng/dL, range 1.70-15.80 ng/dL) showed a seasonal distribution with higher levels in summer and a direct correlation to environmental temperatures and daylight duration. LH levels (mean 4.64 ± 2.54 IU/L, range 1.00-15.00 IU/L) presented 2 peaks of secretion in autumn and spring, independently from environmental parameters. FSH levels (mean 5.51 ± 3.24 IU/L) did not show any seasonal distribution. A clear seasonal fluctuation of both LH and testosterone was demonstrated in a large cohort of adult men, although a circannual seasonality of hypothalamic-pituitary-gonadal hormones in humans could be not strictly evolutionarily required. Testosterone seasonality seems independent from LH fluctuations, which could be regulated by cyclic central genes expression, and more sensible to environmental temperatures and daylight duration.

Seasonal Reproduction in Vertebrates: Melatonin Synthesis, Binding, and Functionality Using Tinbergen's Four Questions

One of the many functions of melatonin in vertebrates is seasonal reproductive timing. Longer nights in winter correspond to an extended duration of melatonin secretion. The purpose of this review is to discuss melatonin synthesis, receptor subtypes, and function in the context of seasonality across vertebrates. We conclude with Tinbergen's Four Questions to create a comparative framework for future melatonin research in the context of seasonal reproduction.

Multiple signaling pathways convey central and peripheral signals to regulate pituitary function: Lessons from human and non-human primate models

The anterior pituitary gland is a key organ involved in the control of multiple physiological functions including growth, reproduction, metabolism and stress. These functions are controlled by five distinct hormone-producing pituitary cell types that produce growth hormone (somatotropes), prolactin (lactotropes), adrenocorticotropin (corticotropes), thyrotropin (thyrotropes) and follicle stimulating hormone/luteinizing hormone (gonadotropes). Classically, the synthesis and release of pituitary hormones was thought to be primarily regulated by central (neuroendocrine) signals. However, it is now becoming apparent that factors produced by pituitary hormone targets (endocrine and non-endocrine organs) can feedback directly to the pituitary to adjust pituitary hormone synthesis and release. Therefore, pituitary cells serve as sensors to integrate central and peripheral signals in order to fine-tune whole-body homeostasis, although it is clear that pituitary cell regulation is species-, age- and sex-dependent. The purpose of this review is to provide a comprehensive, general overview of our current knowledge of both central and peripheral regulators of pituitary cell function and associated intracellular mechanisms, focusing on human and non-human primates.

Melatonin regulates somatotrope and lactotrope function through common and distinct signaling pathways in cultured primary pituitary cells from female primates

Melatonin (MT) is secreted by the pineal gland and exhibits a striking circadian rhythm in its release. Depending on the species studied, some pituitary hormones also display marked circadian/seasonal patterns and rhythms of secretion. However, the precise relationship between MT and pituitary function remains controversial, and studies focusing on the direct role of MT in normal pituitary cells are limited to nonprimate species. Here, adult normal primate (baboons) primary pituitary cell cultures were used to determine the direct impact of MT on the functioning of all pituitary cell types from the pars distalis. MT increased GH and prolactin (PRL) expression/release in a dose- and time-dependent fashion, a response that was blocked by somatostatin. However, MT did not significantly affect ACTH, FSH, LH, or TSH expression/release. MT did not alter GHRH- or ghrelin-induced GH and/or PRL secretions, suggesting that MT may activate similar signaling pathways as ghrelin/GHRH. The effects of MT on GH/PRL release, which are likely mediated through MT1 receptor, involve both common (adenylyl cyclase/protein kinase A/extracellular calcium-channels) and distinct (phospholipase C/intracellular calcium-channels) signaling pathways. Actions of MT on pituitary cells also included regulation of the expression of other key components for the control of somatotrope/lactotrope function (GHRH, ghrelin, and somatostatin receptors). These results show, for the first time in a primate model, that MT directly regulates somatotrope/lactotrope function, thereby lending support to the notion that the actions of MT on these cells might substantially contribute to the define daily patterns of GH and PRL observed in primates and perhaps in humans.

The effectiveness of melatonin for promoting healthy sleep: a rapid evidence assessment of the literature

A systematic review was conducted using Samueli Institute’s Rapid Evidence Assessment of the Literature (REAL^©) process to determine the evidence base for melatonin as an agent to optimize sleep or improve sleep quality, and generalize the results to a military, civilian, or other healthy, active, adult population. Multiple databases were searched yielding 35 randomized controlled trials (RCTs) meeting the review’s inclusion criteria, which were assessed for methodological quality as well as for melatonin effectiveness. The majority of included studies were high quality (83.0%). Overall, according to Grading Recommendations, Assessment Development and Evaluation (GRADE) methodology, weak recommendations were made for preventing phase shifts from jet lag, for improving insomnia in both healthy volunteers and individuals with a history of insomnia, and for initiating sleep and/or improving sleep efficacy. Based on the literature to date, no recommendations for use in shift workers or to improve hormonal phase shift changes in healthy people can be made at this time. Larger and longer-duration RCTs utilizing well characterized products are needed to warrant melatonin recommendations in young, healthy adults.

Opposite influence of light and blindness on pituitary-gonadal function

Some environmental factors may influence the pituitary-gonadal function. Among these, light plays an important role in animals and in humans. The effect of light on the endocrine system is mediated by the pineal gland, through the modulation of melatonin secretion. In fact, melatonin secretion is stimulated by darkness and suppressed by light, thus its circadian rhythm peaks at night. Light plays a favorable action on the hypothalamic-pituitary axis likely inhibiting melatonin secretion, while the exogenous melatonin administration does not seem to impair the hormonal secretions of this axis. The basal and rhythmic pituitary-gonadal hormone secretions are regulated by a central clock gene and some independent clock genes in the peripheral tissues. Light is able to induce the expression of some of these genes, thus playing an important role in regulating the hormonal secretions of pituitary-gonadal axis and the sexual and reproductive function in animals and humans. The lack of light stimulus in blind subjects induces increase in plasma melatonin concentrations with a free-running rhythm of secretion, which impairs the hormonal secretions of pituitary-gonadal axis, causing disorders of reproductive processes in both sexes.

Melatonin reduces lung oxidative stress in patients with chronic obstructive pulmonary disease: a randomized, double-blind, placebo-controlled study

Chronic obstructive pulmonary disease (COPD), a major cause of death and disability, is attributed to an abnormal inflammatory response by the lungs to noxious substances, primarily from cigarette smoke. Although oxidative stress is regarded as central to the pathogenesis of COPD, very few studies have examined the effects of antioxidants in this condition. This was a randomized, double-blind, placebo-controlled study on the effects of melatonin in COPD. Thirty-six consecutive patients with clinically stable moderate to very severe COPD (30 men; mean±S.D.=66.6±7.8yr) were randomized to receive 3mg melatonin (N=18) or placebo for 3 months. Oxidative stress was evaluated by 8-isoprostane levels in exhaled breath condensate at baseline (T0) and after one (T1), two (T2), and three months (T3) of treatment. Additionally, exhaled breath condensate levels of IL-8, dyspnea severity (Medical Research Council scale), lung function (spirometry), and functional exercise capacity (six min walk test) were compared at baseline and after treatment. Patients receiving melatonin showed a decrease in 8-isoprostane (T0: mean±S.E.M.=20.41±2.92pg/mL; T1: 18.56±2.68pg/mL; T2: 12.68±2.04pg/mL; T3: 12.70±2.18pg/mL; P=0.04; repeated measures ANOVA) with significant differences from baseline after 2 (P=0.03) and 3months (P=0.01). Dyspnea was improved by melatonin (P=0.01), despite no significant changes in lung function or exercise capacity. Placebo-treated patients, but not those who were given melatonin, showed an increase in IL-8 (P=0.03). In summary, melatonin administration reduced oxidative stress and improved dyspnea in COPD. Further studies are necessary to determine the potential role for melatonin in the long-term management of these patients.

Melatonin improves sleep and reduces nitrite in the exhaled breath condensate in cystic fibrosis--a randomized, double-blind placebo-controlled study

Cystic fibrosis (CF) is a chronic progressive disorder characterized by repeated episodes of respiratory infection. Impaired sleep is common in CF leading to reduced quality of life. Melatonin, a secretory product of the pineal gland, has an important function in the synchronization of circadian rhythms, including the sleep-wake cycle, and has been shown to possess significant anti-oxidant properties. To evaluate the effects of exogenous melatonin on sleep and inflammation and oxidative stress markers in CF, a randomized double-blind, placebo-controlled study initially involving 20 patients with CF was conducted. One individual failed to conclude the study. All subjects were clinically stable when studied and without recent infectious exacerbation or hospitalization in the last 30 days. Groups were randomized for placebo (n = 10; mean age 12.1 +/- 6.0) or 3 mg melatonin (n = 9; mean age 16.6 +/- 8.26) for 21 days. Actigraphy was performed for 6 days before the start of medication and in the third week (days 14-20) of treatment. Isoprostane and nitrite levels were determined in exhaled breath condensate (EBC) at baseline (day 0) and after treatment (day 21). Melatonin improved sleep efficiency (P = 0.01) and tended to improve sleep latency (P = 0.08). Melatonin reduced EBC nitrite (P = 0.01) but not isoprostane. In summary, melatonin administration reduces nitrite levels in EBC and improves sleep measures in clinically stable CF patients. The failure of melatonin to reduce isoprostane levels may have been a result of the low dose of melatonin used as a treatment.

Long-term follow-up of melatonin treatment in children with ADHD and chronic sleep onset insomnia

We conducted this study to assess long-term melatonin treatment course, effectiveness and safety in children with attention-deficit/hyperactivity disorder (ADHD) and chronic sleep onset insomnia (CSOI). This was conducted by means of a structured questionnaire for the parents. The subjects of this study consisted of participants who previously participated in a randomised clinical trial on melatonin efficacy. The response rate was 93% (94/101). The mean time to follow up was 3.7 yr. No serious adverse events or treatment related co-morbidities were reported. Sixty-five percent of the children still used melatonin daily and 12% occasionally. Temporal discontinuation of treatment resulted in a delay of sleep onset in 92% of the children. Nine percent of the children could discontinue melatonin completely because of improvement of sleep onset insomnia. Long-term melatonin treatment was judged to be effective against sleep onset problems in 88% of the cases. Improvement of behaviour and mood was reported in 71% and 61% respectively. We conclude that melatonin remains an effective therapy on the long term for the treatment of CSOI in children with ADHD and has no safety concerns regarding serious adverse events or treatment related co-morbidity. Discontinuation of melatonin treatment usually leads to a relapse of sleep onset insomnia and in resuming melatonin treatment, even after several years of treatment.

New approaches in the management of insomnia: weighing the advantages of prolonged-release melatonin and synthetic melatoninergic agonists

Hypnotic effects of melatonin and melatoninergic drugs are mediated via MT(1) and MT(2) receptors, especially those in the circadian pacemaker, the suprachiasmatic nucleus, which acts on the hypothalamic sleep switch. Therefore, they differ fundamentally from GABAergic hypnotics. Melatoninergic agonists primarily favor sleep initiation and reset the circadian clock to phases allowing persistent sleep, as required in circadian rhythm sleep disorders. A major obstacle for the use of melatonin to support sleep maintenance in primary insomnia results from its short half-life in the circulation. Solutions to this problem have been sought by developing prolonged-release formulations of the natural hormone, or melatoninergic drugs of longer half-life, such as ramelteon, tasimelteon and agomelatine. With all these drugs, improvements of sleep are statistically demonstrable, but remain limited, especially in primary chronic insomnia, so that GABAergic drugs may be indicated. Melatoninergic agonists do not cause next-day hangover and withdrawal effects, or dependence. They do not induce behavioral changes, as sometimes observed with z-drugs. Despite otherwise good tolerability, the use of melatoninergic drugs in children, adolescents, and during pregnancy has been a matter of concern, and should be avoided in autoimmune diseases and Parkinsonism. Problems and limits of melatoninergic hypnotics are compared.

Mechanisms of Disease: late-onset hypogonadism

Late-onset hypogonadism (formerly called the andropause) is a clinical and biochemical syndrome associated with advancing age, which is characterized by typical signs and symptoms and a deficiency in serum testosterone levels. Age-related hypoandrogenism in the male is a result of the interaction of hypothalamopituitary and testicular factors. The hypothalamic pulsatile secretion of gonadotropin-releasing hormone is blunted, due to increased hypothalamic sensitivity to inhibition by steroids, but the responsiveness of the pituitary gonadotrophs seems to be intact. In addition, testicular volume as well as Leydig cell mass and reserve function are diminished. Taken together, these mechanisms result in reduced testosterone secretion and the loss of nycthemeral variability.

Testosterone Replacement Therapy for Treatment Refractory Cluster Headache

OBJECTIVES

To describe the clinical characteristics and laboratory findings of cluster headache patients whose headaches responded to testosterone replacement therapy.

BACKGROUND

Current evidence points to hypothalamic dysfunction, with increased metabolic hyperactivity in the region of the suprachiasmatic nucleus, as being important in the genesis of cluster headaches. This is clinically borne out in the circadian and diurnal behavior of these headaches. For years it has been recognized that male cluster headache patients appear overmasculinized. Recent neuroendocrine and sleep studies now point to an association between gonadotropin and corticotropin levels and hypothalamically entrained pineal secretion of melatonin.

RESULTS

Seven male and 2 female patients, seen between July 2004 and February 2005, and between the ages of 32 and 56, are reported with histories of treatment resistant cluster headaches accompanied by borderline low or low serum testosterone levels. The patients failed to respond to individually tailored medical regimens, including melatonin doses of 12 mg a day or higher, high flow oxygen, maximally tolerated verapamil, antiepileptic agents, and parenteral serotonin agonists. Seven of the 9 patients met 2004 International Classification for the Diagnosis of Headache criteria for chronic cluster headaches; the other 2 patients had episodic cluster headaches of several months duration. After neurological and physical examination all patients had laboratory investigations including fasting lipid panel, PSA (where indicated), LH, FSH, and testosterone levels (both free and total). All 9 patients demonstrated either abnormally low or low, normal testosterone levels. After supplementation with either pure testosterone in 5 of 7 male patients or combination testosterone/estrogen therapy in both female patients, the patients achieved cluster headache freedom for the first 24 hours. Four male chronic cluster patients, all with abnormally low testosterone levels, achieved remission.

CONCLUSIONS

Abnormal testosterone levels in patients with episodic or chronic cluster headaches refractory to maximal medical management may predict a therapeutic response to testosterone replacement therapy. In the described cases, diurnal variation of attacks, a seasonal cluster pattern, and previous, transient responsiveness to melatonin therapy pointed to the hypothalamus as the site of neurological dysfunction. Prospective studies pairing hormone levels and polysomnographic data are needed.

Melatonin effects on luteinizing hormone in postmenopausal women: a pilot clinical trial NCT00288262

BACKGROUND

In many mammals, the duration of the nocturnal melatonin elevation regulates seasonal changes in reproductive hormones such as luteinizing hormone (LH). Melatonin's effects on human reproductive endocrinology are uncertain. It is thought that the same hypothalamic pulse generator may both trigger the pulsatile release of GnRH and LH and also cause hot flashes. Thus, if melatonin suppressed this pulse generator in postmenopausal women, it might moderate hot flashes. This clinical trial tested the hypothesis that melatonin could suppress LH and relieve hot flashes.

METHODS

Twenty postmenopausal women troubled by hot flashes underwent one week of baseline observation followed by 4 weeks of a randomized controlled trial of melatonin or matched placebo. The three randomized treatments were melatonin 0.5 mg 2.5-3 hours before bedtime, melatonin 0.5 mg upon morning awakening, or placebo capsules. Twelve of the women were admitted to the GCRC at baseline and at the end of randomized treatment for 24-hour sampling of blood for LH. Morning urine samples were collected twice weekly to measure LH excretion. Subjective responses measured throughout baseline and treatment included sleep and hot flash logs, the CESD and QIDS depression self-ratings, and the SAFTEE physical symptom inventory.

RESULTS

Urinary LH tended to increase from baseline to the end of treatment. Contrasts among the 3 randomized groups were statistically marginal, but there was relative suppression combining the groups given melatonin as contrasted to the placebo group (p < 0.01 one-tailed, Mann-Whitney U = 14). Similar but not significant results were seen in blood LH. There were no significant contrasts among groups in hot flashes, sleep, depression, or side-effect measures and no significant adverse effects of any sort.

CONCLUSION

The data are consistent with the hypothesis that melatonin suppresses LH in postmenopausal women. An effect related to the duration of nocturnal melatonin elevation is suggested. Effects of melatonin on reproductive endocrinology should be studied further in younger women and in men. Larger studies of melatonin effects on postmenopausal symptoms would be worthwhile.

Altered melatonin secretion in hypogonadal men: clinical evidence

The pineal gland, through the rhythmic production of melatonin, seems to play an important role in the control of the reproductive function of many vertebrate species. In contrast, the effects of the pineal gland in humans and the relationship between gonadotropins and melatonin secretion are not yet clarified. On the basis of these considerations, the aim of the present study was to clarify whether melatonin serum concentrations were altered in males with different hypothalamo-pituitary-gonadal disturbances, in comparison to normal individuals. We have studied 36 individuals divided into three groups according to their gonadotropin status: normals, hypogonadotropic hypogonadism and hypergonadotropic hypogonadism. They were submitted to blood sample withdrawal at 03.00, 11.00 and 19.00 h for melatonin determination according to a radioimmunological method, without extraction of the sample. The results obtained in the present study suggest the existence of an interaction between the pituitary and the pineal gland. In fact, in the case of hypersecretion of gonadotropins, nocturnal melatonin release is reduced, while night melatonin secretion is increased in the opposite situation (hypogonadotropic hypogonadism). Both these endocrine pathologies are characterized by a reduced sexual steroid secretion; for that reason, this reduction cannot be regarded as responsible for the two opposite dysfunctions of melatonin release. In conclusion, our study shows that darkness-dependent release of melatonin in males with hypogonadotropic hypogonadism is significantly higher in comparison with the healthy men, while it is significantly reduced in patients with hypergonadotropic hypogonadism. A strong significant negative correlation is also found between gonadotropins and melatonin release.

Could seasonal variation in testosterone levels in men be related to sleep?

We have previously reported seasonal variations in both total and free testosterone in men living in north Norway. The aim of this cross-sectional study was to determine whether seasonal variation in testosterone also occurs in men living in geographical areas with less extreme seasonal variation in sunlight and temperature. In 915 men aged 24-91 years from Rancho Bernardo, a suburb of San Diego in southern California, we found that neither total nor bioavailable testosterone varied by season, with or without adjustments for age and anthropometric measurements. Of all examined covariates, only physical activity showed a seasonal variation, with a peak in August (p < 0.001), and adjusting for physical activity did not change the lack of seasonal variation in testosterone. In addition, there was no association between testosterone and mean air temperature, or testosterone and possible hours of sunshine. We conclude that men living in southern California show no seasonal variation in testosterone levels. One possible explanation, besides the difference in climate, for the diverging findings between our previous study and the present study is different sleep patterns.

Seasonal variation of testosterone and waist to hip ratio in men: the Tromsø study

Studies of seasonal variation in male testosterone levels show contradictory results. We report here a cross-sectional study of the seasonal variation in total and free testosterone, LH, and SHBG levels in 1548 men living in north Norway, a population exposed to a wide seasonal variation in temperature and daylight. Total testosterone showed a bimodal seasonal variation (P < 0.001) with a small peak in February, the nadir in June, and a more prominent peak in October and November. Free testosterone also showed a significant seasonal pattern (P < 0.001), with the peak in December and the nadir in August. These patterns persisted after adjusting for age and waist to hip ratio (P < 0.001). Lowest testosterone levels occurred in months with the highest temperatures and longest hours of daylight. Waist to hip ratio paralleled the change in daylight and temperature, with the highest values during the summer and was thus inversely related to the seasonal testosterone variation. The variations in hormone levels were large, with a 31% difference between the lowest and highest monthly mean level of free testosterone. Prospective studies are needed to establish the direction of the association and its etiology.

Seminal plasma melatonin and gonadal steroids concentrations in normal men

The authors determined semen quality and the concentrations of estradiol, testosterone, and melatonin in blood and seminal plasma of 8 normal men. To investigate the reproducibility of these parameters, semen analysis and hormone concentrations were determined on 3 occasions, 6 weeks apart. All 8 men had normal semen analysis. Blood melatonin (9.7-45.4 pg/mL) and testosterone (3.5-12.3 ng/mL) levels were significantly higher than the comparable seminal plasma levels (0.6-5.0 pg/mL, p <.02; 0.1-0.9 ng/mL, p <.0001, respectively). Seminal plasma estradiol levels (46.9-91.3 pg/mL) were significantly higher than the blood levels (13.3-44.7 pg/mL) (p <.0001). The intraindividual variations in seminal plasma estradiol levels ranged between 8.7 and 13.8%. There was no correlation between sperm concentration, motility or morphology and blood or seminal plasma hormone levels. Also, blood and seminal plasma hormone levels were not correlated. These results indicate that in normospermic men seminal plasma estradiol levels are higher than blood hormone levels, suggesting local production of estradiol. This may imply that estrogen and/or the balance andorgen/estrogen is important in normal human spermatogenesis.

Increased 6-sulfatoxymelatonin excretion in women with polycystic ovary syndrome

OBJECTIVE

To determine melatonin production in hyperandrogenic women.

DESIGN

Controlled prospective study.

SETTING

Outpatients in an academic medical center.

PATIENT(S)

Twenty-two women with polycystic ovary syndrome (PCOS), 20 women with idiopathic hirsutism, and 15 age-matched individuals who had similar body mass indexes as controls.

INTERVENTION(S)

Fasting blood samples and 24-hour urinary samples were obtained from all participants.

MAIN OUTCOME MEASURE(S)

All participants provided serum samples for the measurement of LH, FSH, testosterone, E(2), DHEAS, 17 alpha-hydroxyprogesterone (17-OHP), and insulin levels, as well as urinary 6-sulfatoxymelatonin (aMT6s).

RESULT(S)

Women with PCOS had higher aMT6s, testosterone, LH/FSH ratio, and insulin values than either women with idiopathic hirsutism or control women. Testosterone inversely correlated with aMT6s in PCOS. Regression analysis revealed that only testosterone was an important determinant of aMT6s in PCOS.

CONCLUSION(S)

Women with PCOS have increased melatonin production.

Photoperiodism in humans and other primates: evidence and implications

Most of the anatomical and molecular substrates of the system that encodes changes in photoperiod in the duration of melatonin secretion, and the receptor molecules that read this signal, have been shown to be conserved in monkeys and humans, and the functions of this system appear to be intact from the level of the retina to the level of the melatonin-duration signal of change of season. While photoperiodic seasonal breeding has been shown to occur in monkeys, it remains unclear whether photoperiod and mediation of photoperiod's effects by melatonin influence human reproduction. Epidemiological evidence suggests that inhibition of fertility by heat in men in summer contributes to seasonal variation in human reproduction at lower latitudes and that stimulation of fertility by lengthening of the photoperiod in spring contributes to the variation at higher latitudes. Parallels between the seasonality of human reproduction and seasonal affective disorder suggest that they may be governed by common biological processes. Historical and experimental evidence indicates that human responses to seasonal changes in the natural photoperiod may have been more robust prior to the Industrial Revolution and that subsequently they have been increasingly suppressed by alterations of the physical environment.