Opposite influence of light and blindness on pituitary-gonadal function

Association of screen exposure/sedentary behavior and precocious puberty/early puberty

Background

In recent years, with the development of society, children's daily exposure to screen time has gradually increased. Screen exposure and sedentary behavior have brought a host of harms to children's lives. The aim of this study was to explore the effects of screen exposure and sedentary behavior on precocious puberty and early development.

Methods

This is a cross-sectional study in the school-based population. A total of 3,560 children were recruited from Qufu City, Shandong province using multistage stratified cluster random sampling. All study subjects had a physical examination by professional pediatricians in October 2019, and were investigated with health questionnaires. Precocious puberty is defined as development of secondary sexual signs in boys before 9 years or in girls before 8 years. Screen time was calculated as the average of screen time on weekdays and weekend days, and sedentary time was calculated as the average of sedentary time on weekdays and weekend days. After adjusting for potential confounders, logistic regression was used to examine the association between screen exposure and sedentary behavior and early puberty and precocious puberty.

Results

Sedentary time was a risk factor for precocious puberty and early development (OR = 1.428, 95% CI = 1.087-1.876) in girls without adjustment. No significant association was found between screen exposure and early puberty and early development both in girls and boys.

Conclusions

Excessive sedentary behavior was associated with an increased risk of early puberty, especially in girls, while there was no significant association between screen exposure and early puberty and early development. In addition, further longitudinal investigations are needed to determine the causal relationship between screen exposure, sedentary behavior and precocious puberty.

Chrono-Endocrinology in Clinical Practice: A Journey from Pathophysiological to Therapeutic Aspects

This review was aimed at collecting the knowledge on the pathophysiological and clinical aspects of endocrine rhythms and their implications in clinical practice, derived from the published literature and from some personal experiences on this topic. We chose to review, according to the PRISMA guidelines, the results of original and observational studies, reviews, meta-analyses and case reports published up to March 2024. Thus, after summarizing the general aspects of biological rhythms, we will describe the characteristics of several endocrine rhythms and the consequences of their disruption, paying particular attention to the implications in clinical practice. Rhythmic endocrine secretions, like other physiological rhythms, are genetically determined and regulated by a central hypothalamic CLOCK located in the suprachiasmatic nucleus, which links the timing of the rhythms to independent clocks, in a hierarchical organization for the regulation of physiology and behavior. However, some environmental factors, such as daily cycles of light/darkness, sleep/wake, and timing of food intake, may influence the rhythm characteristics. Endocrine rhythms are involved in important physiological processes and their disruption may cause several disorders and also cancer. Thus, it is very important to prevent disruptions of endocrine rhythms and to restore a previously altered rhythm by an early corrective chronotherapy.

Fluctuations in Seminal Quality throughout the Year: How do Temperature, Humidity and Atmospheric Pressure Impact on Human Sperm Quality?

Background

Most studies evaluating the possible seasonal variation of semen quality have considered temperature as the only causal factor.

Aims

To assess possible seasonality in sperm quality and associations between semen parameters and several meteorological variables (temperature, humidity, apparent temperature and atmospheric pressure) in a large cohort of andrological patients.

Settings and Design

This was a retrospective, cross-sectional and correlational/descriptive study.

Materials and Methods

Patients (n: 15665) were categorised into four groups (summer, winter, spring and autumn) according to the date of assistance at the fertility centre. Daily values of temperature, apparent temperature, humidity and atmospheric pressure were provided by the National Weather System and were calculated as the average of the 74 days previous to semen collection (spermatogenic cycle).

Statistical Analysis Used

As appropriate, the results were analysed by analysis of variance/Kruskal-Wallis, Chi-square test, t-test/Mann-Whitney, forward conditional regression model and Spearman/Pearson's correlations.

Results

We detected seasonality effects on sperm count, total sperm count and total motile sperm count, with the highest values in winter and the lowest in summer. Correlation analysis showed that temperature, apparent temperature and humidity negatively correlated with semen parameters, being humidity the most powerful predictive meteorological variable.

Conclusion

Sperm quality is influenced by seasons; increased environmental temperature and humidity negatively affect semen quality.

Daytime Lipid Metabolism Modulated by CLOCK Gene Is Linked to Retinal Ganglion Cells Damage in Glaucoma

Lipid metabolism is intimately linked to circadian mechanisms and light signaling. Deteriorated photic transduction because of retinal ganglion cell (RGC) loss occurring with glaucoma progression reduces perceived light amplitude, causing circadian disruption. To investigate associations with RGCs, total cholesterol (TC), its low-density (LDL-C) and high-density (HDL-C) fractions, and triglycerides (TG) were measured, under a controlled meal regimen, during daytime hours in 114 patients diagnosed with primary open-angle glaucoma (POAG). RGC damage was assessed by high-definition optical coherence tomography (HD-OCT). Analysis of eight clock, clock-related, and melatonin receptor gene polymorphisms was performed on 19 patients. RGC loss was associated with changes in lipid metabolism in a time-dependent manner. Morning (08:00) values of HDL-C (r = 0.613, p < 0.0001) and TG (r = 0.568, p < 0.0001) correlated positively with RGC global loss, while LDL-C at 08:00 had a weak correlation (r = 0.235; p = 0.012) but showed a strong correlation in the evening (20:00) (r = 0.533, p < 0.0001). The morning–evening gradients (MEGs, changes at 20:00 versus 08:00) in TC and LDL-C changed sign from a negative to a positive association in patients exceeding the 15% two-eye mean GLV threshold. MEG (LDL-C higher in the evening than in the morning) was positive only in POAG patients with the CLOCK_3111 TT genotype.

Early menarche in visually impaired girls: evidence and hypothesis of light-dark cycle disruption and blindness effect on puberty onset

Puberty onset is tightly regulated by a broad spectrum of neuroendocrine signals and peripheral stimuli which coordinate the hypothalamic-pituitary-gonadal (HPG) axis activation. Numerous studies suggest that light stimulation influences HPG axis function; however, the effect of blindness on puberty timing remains controversial. Given that menarche is a suitable marker for sexual development initiation, the evaluation of the age at which blind girls attain it allows to indirectly assess the effect of light-dark cycle disruption on pubertal development. The present investigation aimed to review the evidence regarding menarcheal age drift in visually impaired girls, as well as to discuss the findings based on the existing hypotheses of the physiological mechanisms linking the light-dark cycle and photic sensitivity loss to the onset of puberty. Eleven studies were retrieved from a literature search conducted in PubMed, Scopus, ScienceDirect, SpringerLink, and Google Scholar databases. Eight studies concluded that light perception impairment is related to a moderately earlier age at menarche. Moreover, the evidence gathered in this review suggests a positive association between the degree of light perception loss and precocious menarcheal onset; yet, no conclusive outcomes were found regarding menarche advancement in acquired versus congenital blindness. We encourage further research aiming to elucidate the physiological mechanism underlying photosensitive regulation and blindness effect on the neuroendocrine pathways involved in human sexual maturation.

The effect of light on follicular development in laying hens

OBJECTIVE

The oxidative stress status and changes of chicken ovary tissue after shading were studied, to determine the mechanism of the effect of shading on follicular development.

METHODS

Twenty healthy laying hens (40 weeks old) with uniform body weight and the same laying rate were randomly divided into two groups (the shading group and normal light group). In the shading group, the cage was covered to reduce the light intensity inside the cage to 0 without affecting ventilation or food intake. The normal lighting group received no additional treatment. After 7 days of shading, oxidative stress related indicators and gene expression were detected.

RESULTS

Analysis of paraffin and ultrathin sections showed that apoptosis of ovarian granulosa cells (GCs) increased significantly after light shading. Enzyme linked immunosorbent assay results revealed that the levels of total antioxidant capacity, malondialdehyde, superoxide dismutase (SOD), glutathione, catalase (CAT), and other substances in the sera, livers, ovaries, and follicular GCs of laying hens increased significantly after shading for 7 days; and reactive oxygen species (ROS) levels in the livers of laying hens also increased significantly. ROS in the serum, ovarian and GCs also increased. After shading for 7 days, the levels of 8-hydroxy-2 deoxyguanosine in the sera and ovarian tissues of laying hens increased significantly. Cell counting kit-8 detection showed that the proliferation activity of GCs in layer follicles decreased after shading for 7 days; the expression level of the anti-apoptotic gene B-cell lymphoma-2 in ovarian tissue and follicular GCs was significantly reduced, and the expression levels of pro-apoptotic caspase 3 (casp3), and SOD, glutathione peroxidase 2 (GPX2), and CAT were all significantly increased.

CONCLUSION

Oxidative stress induced by shading light has a serious inhibitory effect on follicular development during reproduction in laying hens.

Effect of a health education program on puberty knowledge among visually impaired female adolescent students

Background: One of the most important aspects of life is reproductive health, which receives less attention in public policy considerations because of its sociopolitical sensitivities. The aim of this study was to evaluate the effect of a designed health education program on knowledge about puberty health among visually impaired female adolescent students during 2011 and 2015.

Methods: This quasi-experimental study was conducted on 100 visually impaired female students aged 10 to 19 years. Data collection tool was a researcher-made questionnaire. Participants were recruited using convenience sampling method from Narjes educational center in Tehran. The educational needs assessments survey was used to learn about important issues and problems faced by this group to design effective educational programs. The effectiveness of the designed program was assessed by comparing the students' knowledge at the baseline and at 1-month follow-up. Data were analyzed in SPSS V.21 by using parametric descriptive statistics. The significant level was set as p<0.05

Results: The results showed that the puberty knowledge of participants was increased in all educational domains after intervention compared to the baseline (p<0.05). The knowledge about the onset of puberty changes showed the highest increase (from 2.02 at baseline to 7.51 at follow-up) and the knowledge about personal hygiene had the least change after the intervention (from 6.67 to 8.23). The majority of students did not have any information resources regarding puberty health, and about one quarter of them reported their mother as the main resource of puberty information.

Conclusion: Providing educational programs during puberty has a crucial role in young girls’ knowledge increase. Providing a continuous health educational program that is tailored to the needs of this group of students using suitable strategies is recommended.

Chronothyroidology: Chronobiological Aspects in Thyroid Function and Diseases

Chronobiology is the scientific discipline which considers biological phenomena in relation to time, which assumes itself biological identity. Many physiological processes are cyclically regulated by intrinsic clocks and many pathological events show a circadian time-related occurrence. Even the pituitary–thyroid axis is under the control of a central clock, and the hormones of the pituitary–thyroid axis exhibit circadian, ultradian and circannual rhythmicity. This review, after describing briefly the essential principles of chronobiology, will be focused on the results of personal experiences and of other studies on this issue, paying particular attention to those regarding the thyroid implications, appearing in the literature as reviews, metanalyses, original and observational studies until 28 February 2021 and acquired from two databases (Scopus and PubMed). The first input to biological rhythms is given by a central clock located in the suprachiasmatic nucleus (SCN), which dictates the timing from its hypothalamic site to satellite clocks that contribute in a hierarchical way to regulate the physiological rhythmicity. Disruption of the rhythmic organization can favor the onset of important disorders, including thyroid diseases. Several studies on the interrelationship between thyroid function and circadian rhythmicity demonstrated that thyroid dysfunctions may affect negatively circadian organization, disrupting TSH rhythm. Conversely, alterations of clock machinery may cause important perturbations at the cellular level, which may favor thyroid dysfunctions and also cancer.

Endocrine rhythms and sport: it is time to take time into account

BACKGROUND

Studies of time-related biological phenomena have contributed to establishing a new scientific discipline, the chronobiology, which considers biological phenomena in relation to time. Sports activity profoundly affects the temporal organization of the organism and endocrine rhythms play a key role in the chronoorganization of individuals and are particularly important for correct physical activity. Correctly reading rhythmic hormonal variations of the human organism opens new horizons to sports medicine.

OBJECTIVE

This review is aimed at clarifying the relationship between endocrine rhythms and sports activities on the basis of the latest data in the literature.

METHOD

Data acquisition was obtained from three databases (PubMed, Scopus and SPORTDiscus), paying particular attention to reviews, meta-analysis, original and observational studies on this issue.

RESULTS

After the description of the general characteristics and parameters of biological rhythms, the main endocrine rhythms will be described, highlighting in particular the interrelationships with sports activity and focusing on the factors which can affect negatively their characteristics and consequently the psychophysical performances of the athletes.

CONCLUSION

Knowledge of this issue may allow establishing the best form of competitive or amateur activity, through the collaboration of an informed athlete and a sports physician attentive to biological rhythms. By taking into account that alteration of physiological rhythmic temporal organization can favour the onset of important diseases, including cancer, this will lead to the expected performances without impairing the correct chronoorganization of the athlete.

How much does obesity affect the male reproductive function?

Obesity is considered a worldwide epidemic disease. Many pathological conditions have been associated to obesity but the evidence relating to impaired fertility in males with obesity are contrasting. The aim of this review was to evaluate the interplay between obesity and male fertility, analyzing evidence from in vitro and in vivo studies to clinical trials. Obesity seems to be responsible of secondary hypogonadism. Here, we propose a new classification including central, peripheral and testicular factors that may affect the hypothalamic-pituitary-gonadal axis. Moreover, some studies demonstrated a direct action of obesity on sperm count and sperm characteristics, mediated by impaired Sertoli cells function, increased scrotal temperature, oxidative stress and accumulation of toxic substances and liposoluble endocrine disruptors in fat tissue. Recent studies have explored obesity-related epigenetic effects in sperm cells which may cause diseases in offspring. Moreover, not only in females but also males, obesity has been linked to reduced outcomes of in vitro fertilization, with a reduction of pregnancy rate and an increase of pregnancy loss. Finally, we reviewed the effects of weight modifications through diet or bariatric surgery on obesity-related reproductive dysfunction. In this regard, several studies have demonstrated that weight loss has been associated with a restoration of gonadal hormones levels.

Integration of Circadian and Metabolic Control of Reproductive Function

Optimal fertility in humans and animals relies on the availability of sufficient metabolic fuels, information about which is communicated to the brain via levels of the hormones leptin and insulin. The circadian clock system is also critical; this input is especially evident in the precise timing of the female-specific surge of GnRH and LH secretion that triggers ovulation the next day. Chronodisruption and metabolic imbalance can both impair reproductive activity, and these two disruptions exacerbate each other, such that they often occur simultaneously. Kisspeptin neurons located in the anteroventral periventricular nucleus of the hypothalamus are able to integrate both circadian and metabolic afferent inputs and use this information to modulate the timing and magnitude of the preovulatory GnRH/LH surge. In an environment in which exposure to high caloric diets and chronodisruptors such as artificial night lighting, shift work, and transmeridian travel have become the norm, the implications of these factors for couples struggling to conceive deserve closer attention and more public education.

Nutritional status and the gonadotrophic response to a polar expedition

Polar expeditions have been associated with changes in the hypothalamic–pituitary–testicular axis consistent with central hypogonadism (i.e., decreased testosterone, luteinising hormone (LH), and follicle stimulating hormone (FSH)). These changes are typically associated with body mass loss. Our aim was to evaluate whether maintenance of body mass during a polar expedition could mitigate against the development of central hypogonadism. Male participants (n = 22) from a 42-day expedition (British Services Antarctic Expedition 2012) volunteered to take part in the study. Body mass, body composition, and strength data were recorded pre- and postexpedition in addition to assessment of serum testosterone, LH, FSH, thyroid hormones, insulin-like growth factor 1 (IGF-1), and trace elements. Energy provision and energy expenditure were assessed at mid- and end-expedition. Daily energy provision was 6335 ± 149 kcal·day−1. Estimated energy expenditure midexpedition was 5783 ± 1690 kcal·day−1. Body mass and percentage body fat did not change between pre- and postexpedition. Total testosterone (nmol·L−1) (14.0 ± 4.9 vs. 17.3 ± 4.0, p = 0.006), calculated free testosterone (pmol·L−1) (288 ± 82 vs. 350 ± 70, p = 0.003), and sex hormone binding globulin (nmol·L−1) (33 ± 12 vs. 36 ± 11, p = 0.023) concentrations increased. LH and FSH remained unchanged. Thyroid stimulating hormone (TSH; IU·L−1) (2.1 ± 0.8 vs. 4.1 ± 2.1, p < 0.001) and free triiodothyronine (FT3; IU·L−1) (5.4 ± 0.4 vs. 6.1 ± 0.8, p < 0.001) increased while free thyroxine, IGF-1, and trace elements remained unchanged. Hand-grip strength was reduced postexpedition but static lift strength was maintained. Maintenance of body mass and nutritional status appeared to negate the central hypogonadism previously reported from polar expeditions. The elevated TSH and free FT3 were consistent with a previously reported “polar T3 syndrome”.