Somatotropic and gonadotropic axes linkages in infancy, childhood, and the puberty-adult transition

A review of complex hormone regulation in thyroid cancer: novel insights beyond the hypothalamus-pituitary-thyroid axis

Like the ovaries and prostate, the thyroid exhibits characteristic hormone secretion and regulation. Thyroid cancer (TC), especially differentiated thyroid carcinoma, has typical sex-specific and age-specific hormone-driven clinical features. Previous research has primarily focused on the effects of thyroid stimulating hormone, thyroid hormones, and estrogens on the onset and progression of TC, while the roles of growth hormone (GH), androgens, and glucocorticoids have largely been overlooked. Similarly, few studies have investigated the interactions between hormones and hormone systems. In fact, numerous studies of patients with acromegaly have shown that serum levels of GH and insulin-like growth factor-1 (IGF-1) may be associated with the onset and progression of TC, although the influences of age, sex, and other risk factors, such as obesity and stress, remain unclear. Sex hormones, the GH/IGF axis, and glucocorticoids are likely involved in the onset and progression of TC by regulating the tumor microenvironment and metabolism. The aim of this review was to clarify the roles of hormones and hormone systems in TC, especially papillary thyroid carcinoma, as references for further investigations.

Mini-Puberty, Physiological and Disordered: Consequences, and Potential for Therapeutic Replacement

There are 3 physiological waves of central hypothalamic-pituitary-gonadal (HPG) axis activity over the lifetime. The first occurs during fetal life, the second-termed "mini-puberty"-in the first months after birth, and the third at puberty. After adolescence, the axis remains active all through adulthood. Congenital hypogonadotropic hypogonadism (CHH) is a rare genetic disorder characterized by a deficiency in hypothalamic gonadotropin-releasing hormone (GnRH) secretion or action. In cases of severe CHH, all 3 waves of GnRH pulsatility are absent. The absence of fetal HPG axis activation manifests in around 50% of male newborns with micropenis and/or undescended testes (cryptorchidism). In these boys, the lack of the mini-puberty phase accentuates testicular immaturity. This is characterized by a low number of Sertoli cells, which are important for future reproductive capacity. Thus, absent mini-puberty will have detrimental effects on later fertility in these males. The diagnosis of CHH is often missed in infants, and even if recognized, there is no consensus on optimal therapeutic management. Here we review physiological mini-puberty and consequences of central HPG axis disorders; provide a diagnostic approach to allow for early identification of these conditions; and review current treatment options for replacement of mini-puberty in male infants with CHH. There is evidence from small case series that replacement with gonadotropins to mimic "mini-puberty" in males could have beneficial outcomes not only regarding testis descent, but also normalization of testis and penile sizes. Moreover, such therapeutic replacement regimens in disordered mini-puberty could address both reproductive and nonreproductive implications.

Appetite- and Weight-Regulating Neuroendocrine Circuitry in Hypothalamic Obesity

Since hypothalamic obesity (HyOb) was first described over 120 years ago by Joseph Babinski and Alfred Fröhlich, advances in molecular genetic laboratory techniques have allowed us to elucidate various components of the intricate neurocircuitry governing appetite and weight regulation connecting the hypothalamus, pituitary gland, brainstem, adipose tissue, pancreas, and gastrointestinal tract. On a background of an increasing prevalence of population-level common obesity, the number of survivors of congenital (eg, septo-optic dysplasia, Prader-Willi syndrome) and acquired (eg, central nervous system tumors) hypothalamic disorders is increasing, thanks to earlier diagnosis and management as well as better oncological therapies. Although to date the discovery of several appetite-regulating peptides has led to the development of a range of targeted molecular therapies for monogenic obesity syndromes, outside of these disorders these discoveries have not translated into the development of efficacious treatments for other forms of HyOb. This review aims to summarize our current understanding of the neuroendocrine physiology of appetite and weight regulation, and explore our current understanding of the pathophysiology of HyOb.

Mechanisms and predictors of menses resumption once normal weight is reached in anorexia nervosa

BACKGROUND

In cases of Anorexia Nervosa (AN), achieving weight gain recovery beyond the lower limits set by the World Health Organization and normalizing classical nutritional markers appears to be essential for most patients. However, this is not always adequate to restore menstrual cycles. This discrepancy can cause concern for both patients and healthcare providers, and can impact the medical management of these individuals. Thus, the purpose of this study was to assess the ability of anthropometric and hormonal factors to predict the resumption of menstrual cycles in individuals with anorexia nervosa upon reaching a normal body weight.

METHOD

Patients with AN who had achieved a normal Body Mass Index but had not yet resumed their menstrual cycles (referred to as ANRec) were evaluated on two occasions: first at visit 1 and then again 6 months later, provided their body weight remained stable over this period (visit 2). Among the 46 ANRec patients who reached visit 2, they were categorized into two groups: 20 with persistent amenorrhea (PA-ANRec) and 26 who had regained their menstrual cycles (RM-ANRec). Anthropometric measurements, several hormone levels, Luteinizing Hormone (LH) pulsatility over a 4-h period, and LH response to gonadotropin-releasing hormone injection (LH/GnRH) were then compared between the two groups at visit 1.

RESULTS

Patients in the RM-ANRec group exhibited higher levels of follicular stimulating hormone, estradiol, inhibin B, LH/GnRH, and lower levels of ghrelin compared to those in the PA-ANRec group. Analysis of Receiver Operating Characteristic curves indicated that having ≥ 2 LH pulses over a 4-h period, LH/GnRH levels ≥ 33 IU/l, and inhibin B levels > 63 pg/ml predicted the resumption of menstrual cycles with a high degree of specificity (87%, 100%, and 100%, respectively) and sensitivity (82%, 80%, and 79%, respectively).

CONCLUSIONS

These three hormonal tests, of which two are straightforward to perform, demonstrated a high predictive accuracy for the resumption of menstrual cycles. They could offer valuable support for the management of individuals with AN upon achieving normalized weight. Negative results from these tests could assist clinicians and patients in maintaining their efforts to attain individualized metabolic targets.

TRIAL REGISTRATION

IORG0004981.

Effects of Growth Hormone on Adult Human Gonads: Action on Reproduction and Sexual Function

Growth hormone (GH), which is commonly considered to be a promoter of growth and development, has direct and indirect effects on adult gonads that influence reproduction and sexual function of humans and nonhumans. GH receptors are expressed in adult gonads in some species including humans. For males, GH can improve the sensitivity of gonadotropins, contribute to testicular steroidogenesis, influence spermatogenesis possibly, and regulate erectile function. For females, GH can modulate ovarian steroidogenesis and ovarian angiogenesis, promote the development of ovarian cells, enhance the metabolism and proliferation of endometrial cells, and ameliorate female sexual function. Insulin-like growth factor-1 (IGF-1) is the main mediator of GH. In vivo, a number of the physiological effects of GH are mediated by GH-induced hepatic IGF-1 and local IGF-1. In this review, we highlight the roles of GH and IGF-1 in adult human gonads, clarify potential mechanisms, and explore the efficacy and the risk of GH supplementation in associated deficiency and assisted reproductive technologies. Besides, the effects of excess GH on adult human gonads are discussed as well.

Precocious puberty under stressful conditions: new understanding and insights from the lessons learnt from international adoptions and the COVID-19 pandemic

Neuro-biological variations in the timing of sexual maturation within a species are part of an evolved strategy that depend on internal and external environmental conditions. An increased incidence of central precocious puberty (CPP) has been described in both adopted and "covid-19 pandemic" children. Until recently, it was hypothesised that the triggers for CPP in internationally adopted children were likely to be better nutrition, greater environmental stability, and improved psychological wellbeing. However, following data collected during and after the coronavirus (COVID-19) global pandemic, other possibilities must be considered. In a society with high levels of child wellbeing, the threat to life presented by an unknown and potentially serious disease and the stressful environment created by lockdowns and other public health measures could trigger earlier pubertal maturation as an evolutionary response to favour early reproduction. The main driver for increased rates of precocious and rapidly progressive puberty during the pandemic could have been the environment of "fear and stress" in schools and households. In many children, CPP may have been triggered by the psychological effects of living without normal social contact, using PPE, being near adults concerned about financial and other issues and the fear of getting ill. The features and time of progression of CPP in children during the pandemic are similar to those observed in adopted children. This review considers the mechanisms regulating puberty with a focus on neurobiological and evolutionary mechanisms, and analyses precocious puberty both during the pandemic and in internationally adopted children searching for common yet unconsidered factors in an attempt to identify the factors which may have acted as triggers. In particular, we focus on stress as a potential factor in the early activation of the hypothalamic-pituitary-gonadal axis and its correlation with rapid sexual maturation.

Higher Prepubertal IGF-1 Concentrations Associate to Earlier Pubertal Tempo in Both Sexes

INTRODUCTION

Pubertal onset is triggered by multiple neuroendocrine interactions. The role of prepubertal IGF-1 in this process has not been explored in both sexes. Our objective was to analyze the association of prepubertal IGF-1 concentration with age at thelarche (B2) and menarche (M) in girls and age at gonadarche (G2) in boys.

METHODS

This is a longitudinal study (n = 1,196 boys and girls) within the Growth and Obesity Chilean Cohort Study (GOCS). At age ≈ 6.7 years, blood sample was taken for IGF-1. Subjects were divided into 4 groups according to the onset age of the pubertal event.

RESULTS

Higher prepubertal IGF-1 levels were observed at earlier ages of B2 (p = 0.003) and M onset (p = 0.041). A taller prepubertal height was observed at younger ages of B2 and M (p=<0.001 and 0.002, respectively). The hazard proportional regression models (HR) showed that with an increase of 1 SD in IGF-1, the HR of presenting B2 at younger ages was 1.25, and this association was maintained when adjusted for confounding variables. Similarly, the HR of presenting M at earlier ages was 1.21. This association was maintained only when adjusting for body mass index but not using further confounders. In boys, prepubertal IGF-1 showed a tendency to be significantly higher in children with earlier G2 and taller height (both p < 0.001). The HR of presenting G2 at younger ages was 1.22, and this association was maintained after adjusting for confounders.

CONCLUSIONS

Higher IGF-1 levels in mid-childhood are associated with earlier puberty onset. The role of IGF-1 in the onset of puberty requires further investigation.

Important Hormones Regulating Lipid Metabolism

There is a wide variety of kinds of lipids, and complex structures which determine the diversity and complexity of their functions. With the basic characteristic of water insolubility, lipid molecules are independent of the genetic information composed by genes to proteins, which determine the particularity of lipids in the human body, with water as the basic environment and genes to proteins as the genetic system. In this review, we have summarized the current landscape on hormone regulation of lipid metabolism. After the well-studied PI3K-AKT pathway, insulin affects fat synthesis by controlling the activity and production of various transcription factors. New mechanisms of thyroid hormone regulation are discussed, receptor α and β may mediate different procedures, the effect of thyroid hormone on mitochondria provides a new insight for hormones regulating lipid metabolism. Physiological concentration of adrenaline induces the expression of extrapituitary prolactin in adipose tissue macrophages, which promotes fat weight loss. Manipulation of hormonal action has the potential to offer a new therapeutic horizon for the global burden of obesity and its associated complications such as morbidity and mortality.

Involvement of IGF-1R-PI3K-AKT-mTOR pathway in increased number of GnRH3 neurons during androgen-induced sex reversal of the brain in female tilapia

The neuroplastic mechanism of sex reversal in the fish brain remains unclear due to the difficulty in identifying the key neurons involved. Mozambique tilapia show different reproductive behaviours between sexes; males build circular breeding nests while females hold and brood fertilized eggs in their mouth. In tilapia, gonadotropin-releasing hormone 3 (GnRH3) neurons, located in the terminal nerve, regulate male reproductive behaviour. Mature males have more GnRH3 neurons than mature females, and these neurons have been indicated to play a key role in the androgen-induced female-to-male sex reversal of the brain. We aimed to elucidate the signalling pathway involved in the androgen-induced increase in GnRH3 neurons in mature female tilapia. Applying inhibitors to organotypic cultures of brain slices, we showed that the insulin-like growth factor (IGF)-1 receptor (IGF-1R)/PI3K/AKT/mTOR pathway contributed to the androgen-induced increase in GnRH3 neurons. The involvement of IGF-1 and IGF-1R in 11-ketotestosterone (11-KT)-induced development of GnRH3 neurons was supported by an increase in Igf-1 mRNA shortly after 11-KT treatment, the increase of GnRH3 neurons after IGF-1 treatment and the expression of IGF-1R in GnRH3 neurons. Our findings highlight the involvement of IGF-1 and its downstream signalling pathway in the sex reversal of the tilapia brain.

Common Pathogenetic Mechanisms Underlying Aging and Tumor and Means of Interventions

Recently, there has been an increase in the incidence of malignant tumors among the older population. Moreover, there is an association between aging and cancer. During the process of senescence, the human body suffers from a series of imbalances, which have been shown to further accelerate aging, trigger tumorigenesis, and facilitate cancer progression. Therefore, exploring the junctions of aging and cancer and searching for novel methods to restore the junctions is of great importance to intervene against aging-related cancers. In this review, we have identified the underlying pathogenetic mechanisms of aging-related cancers by comparing alterations in the human body caused by aging and the factors that trigger cancers. We found that the common mechanisms of aging and cancer include cellular senescence, alterations in proteostasis, microbiota disorders (decreased probiotics and increased pernicious bacteria), persistent chronic inflammation, extensive immunosenescence, inordinate energy metabolism, altered material metabolism, endocrine disorders, altered genetic expression, and epigenetic modification. Furthermore, we have proposed that aging and cancer have common means of intervention, including novel uses of common medicine (metformin, resveratrol, and rapamycin), dietary restriction, and artificial microbiota intervention or selectively replenishing scarce metabolites. In addition, we have summarized the research progress of each intervention and revealed their bidirectional effects on cancer progression to compare their reliability and feasibility. Therefore, the study findings provide vital information for advanced research studies on age-related cancers. However, there is a need for further optimization of the described methods and more suitable methods for complicated clinical practices. In conclusion, targeting aging may have potential therapeutic effects on aging-related cancers.

The critical BMI hypothesis for puberty initiation and the gender prevalence difference: Evidence from an epidemiological survey in Beijing, China

BACKGROUND

Although previous studies suggested that there is a certain level of body fat mass before puberty can be initiated, most studies have focused on girls.

OBJECTIVE

To investigate the relationship between precocious puberty and physical growth in school-aged children in Beijing, China.

METHODS

7590 Chinese children (3591 girls and 3999 boys) aged 6-11 years were recruited in Beijing, China. Body mass index (BMI) categories were defined by WHO Child Growth Standards and central obesity were defined by sex-specific waist-to-height ratio cut-offs (≥0.46 for girls, ≥0.48 for boys). Sexual development was assessed using Tanner criteria.

RESULTS

The prevalence of general obesity and central obesity among boys was higher than that in girls. Girls had a significantly higher precocious puberty rate than boys (5.93% vs. 0.87%), particularly in those aged 7 years old (9.20%). Children in the general obesity and central obesity groups have a higher prevalence of precocious puberty and earlier median ages for the attainment of Tanner B₂/T₂. For girls with Tanner stages≥II at 6-year-old and 7-year-old, the mean BMI was equivalent to the 50th centile of a normal 9.9-year-old and 11.9-year-old girl, respectively. The mean BMI of boys with Tanner stages≥II at 7-year-old and 8-year-old was correspondent to the 50th centile of a normal 14-year-old and 15.3-year-old boy, respectively. For girls, general obesity appears to contribute to the risk of the development of precocious puberty to a greater extent than central obesity does. For boys, central obesity, but not general obesity, was an independent risk factor for precocious puberty.

CONCLUSIONS

The prevalence of childhood obesity and precocious puberty was high in China. Precocious puberty was correlated with a large BMI. Boys had a higher threshold of BMI for puberty development than girls. Children with precocious puberty, particularly those with central obesity, should be aware of adverse cardiovascular events.

Growth Hormone/Insulin Growth Factor Axis in Sex Steroid Associated Disorders and Related Cancers

To date, almost all solid malignancies have implicated insulin-like growth factor (IGF) signalling as a driver of tumour growth. However, the remarkable level of crosstalk between sex hormones, the IGF-1 receptor (IGF-1R) and its ligands IGF-1 and 2 in endocrine driven cancers is incompletely understood. Similar to the sex steroids, IGF signalling is essential in normal development as well as growth and tissue homoeostasis, and undergoes a steady decline with advancing age and increasing visceral adiposity. Interestingly, IGF-1 has been found to play a compensatory role for both estrogen receptor (ER) and androgen receptor (AR) by augmenting hormonal responses in the absence of, or where low levels of ligand are present. Furthermore, experimental, and epidemiological evidence supports a role for dysregulated IGF signalling in breast and prostate cancers. Insulin-like growth factor binding protein (IGFBP) molecules can regulate the bioavailability of IGF-1 and are frequently expressed in these hormonally regulated tissues. The link between age-related disease and the role of IGF-1 in the process of ageing and longevity has gained much attention over the last few decades, spurring the development of numerous IGF targeted therapies that have, to date, failed to deliver on their therapeutic potential. This review will provide an overview of the sexually dimorphic nature of IGF signalling in humans and how this is impacted by the reduction in sex steroids in mid-life. It will also explore the latest links with metabolic syndromes, hormonal imbalances associated with ageing and targeting of IGF signalling in endocrine-related tumour growth with an emphasis on post-menopausal breast cancer and the impact of the steroidal milieu.

Temporal characterization of the insulin resistance during puberty in mice

Objectives. The onset of puberty in humans is followed by an increase in insulin resistance and this transient phenomenon decreases at the end of the puberty. However, the insulin resistance during puberty has not been described in mice. Thus, in the present study we performed a temporal characterization of the development of insulin resistance during puberty in male and female C57BL/6 mice.Methods. From the fourth week of life male (n=18) and female (n=32) C57BL/6 wild-type mice were weekly subjected to insulin tolerance tests until the seventh week of life. Blood glucose levels were determined using a glucose meter through samples collected from the tail tip. Vaginal opening was assessed daily in female mice. Preputial separation was determined in a subgroup of males.Results. We observed a transient increase in the area under the curve of the insulin tolerance tests and in basal glycemia in female mice at the time of vaginal opening (between the fourth and fifth week of life) compared with previous and subsequent weeks of pubertal development. In contrast, male mice show no changes in insulin sensitivity during puberty.Conclusions. Our findings demonstrate that the insulin resistance at puberty can also be observed in female mice and this peak occurs at the time of vaginal opening. Our temporal characterization can be used as a reference for future studies that aim to study glucose homeostasis during puberty in rodents.

Growth Hormone Receptor Regulation in Cancer and Chronic Diseases

The GHR signaling pathway plays important roles in growth, metabolism, cell cycle control, immunity, homeostatic processes, and chemoresistance via both the JAK/STAT and the SRC pathways. Dysregulation of GHR signaling is associated with various diseases and chronic conditions such as acromegaly, cancer, aging, metabolic disease, fibroses, inflammation and autoimmunity. Numerous studies entailing the GHR signaling pathway have been conducted for various cancers. Diverse factors mediate the up- or down-regulation of GHR signaling through post-translational modifications. Of the numerous modifications, ubiquitination and deubiquitination are prominent events. Ubiquitination by E3 ligase attaches ubiquitins to target proteins and induces proteasomal degradation or starts the sequence of events that leads to endocytosis and lysosomal degradation. In this review, we discuss the role of first line effectors that act directly on the GHR at the cell surface including ADAM17, JAK2, SRC family member Lyn, Ubc13/CHIP, proteasome, βTrCP, CK2, STAT5b, and SOCS2. Activity of all, except JAK2, Lyn and STAT5b, counteract GHR signaling. Loss of their function increases the GH-induced signaling in favor of aging and certain chronic diseases, exemplified by increased lung cancer risk in case of a mutation in the SOCS2-GHR interaction site. Insight in their roles in GHR signaling can be applied for cancer and other therapeutic strategies.

Relationship Between Age at Adult Height and Knee Mechanics During a Drop Vertical Jump in Men

Background:

Anterior cruciate ligament (ACL) injuries are relatively common among younger athletes, with significant physical, psychological, and financial consequences. Research has largely focused on female athletes by identifying specific risk factors for an ACL injury, including variation in pubertal growth timing. There is less known about risk factors in males, and little is known about the effects of pubertal development on ACL injury risk in men.

Purpose/Hypothesis:

The purpose of this study was to analyze the relationship between an indicator of pubertal growth timing (age at adult height) and biomechanical risk for ACL injuries in men. We hypothesized that earlier age at adult height is correlated with riskier landing biomechanics during a drop vertical jump (DVJ) in men.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

A total of 21 recreationally active male students (age range, 20-33 years) were included. Participants completed a questionnaire on age at adult height and limb dominance, and anthropometric measurements were taken. There were 6 DVJ tests performed, with participants landing on a force plate while digital cameras recorded kinematic data from retroreflective markers placed according to the Helen Hayes marker system. Primary outcomes were sagittal and frontal plane knee kinematics and kinetics during contact. Data were analyzed using Pearson product-moment correlation.

Results:

In both limbs, age at achieving adult height was significantly negatively correlated with knee flexion/extension angle at toe-off (dominant: r = –0.79, P < .01; nondominant: r = –0.74, P < .01) and with peak flexion (dominant: r = –0.63, P < .01; nondominant: r = –0.70, P < .01) and extension (dominant: r = –0.66, P < .01; nondominant: r = –0.56, P = .01) angles during contact. In the nondominant limb, age at adult height was significantly negatively correlated with varus/valgus angle at initial contact (r = –0.43; P = .05) and toe-off (r = –0.44; P = .04) and was positively correlated with peak varus moment during contact (r = 0.42; P = .06). Age at adult height was also positively correlated with peak vertical ground-reaction force (r = 0.58; P < .01).

Conclusion:

Later age at adult height was correlated with riskier landing profiles in this study. This suggests that males with later or longer pubertal growth may have increased mechanical risk for ACL injuries. A better understanding of the effects of pubertal growth on landing biomechanics can improve the early identification of male athletes at greater risk for injuries.

Effects of intrauterine insulin-like growth factor-1 therapy for fetal growth restriction on adult metabolism and body composition are sex specific

Fetal growth restriction (FGR) is associated with compromised growth and metabolic function throughout life. Intrauterine therapy of FGR with intra-amniotic insulin-like growth factor-1 (IGF1) enhances fetal growth and alters perinatal metabolism and growth in a sex-specific manner, but the adult effects are unknown. We investigated the effects of intra-amniotic IGF1 treatment of FGR on adult growth and body composition, adrenergic sensitivity, and glucose-insulin axis regulation. Placental embolization-induced FGR was treated with four weekly doses of 360 µg intra-amniotic IGF1 (FGRI) or saline (FGRS). Offspring were raised to adulthood (18 mo: FGRI, n = 12 females, 12 males; FGRS, n = 13 females, 10 males) alongside offspring from unembolized and untreated sheep (CON; n = 12 females, 21 males). FGRI females had increased relative lean mass compared with CON but not FGRS (P < 0.05; 70.6 ± 8.2% vs. 61.4 ± 8.2% vs. 67.6 ± 8.2%), decreased abdominal adipose compared with CON and FGRS (P < 0.05; 43.7 ± 1.2% vs. 49.3 ± 0.9% vs. 48.5 ± 1.0%), increased glucose utilization compared with FGRS but not CON (P < 0.05; 9.6 ± 1.0 vs. 6.0 ± 0.9 vs. 7.6 ± 0.9 mg·kg^-1·min^-1), and increased β-hydroxybutyric acid:nonesterified fatty acid ratio in response to adrenaline compared with CON and FGRS (P < 0.05; 3.9 ± 1.4 vs. 1.1 ± 1.4 vs. 1.8 ± 1.4). FGRS males were smaller and lighter compared with CON but not FGRI (P < 0.05; 86.8 ± 6.3 vs. 93.5 ± 6.1 vs. 90.7 ± 6.3 kg), with increased peak glucose concentration (10%) in response to a glucose load but few other differences. These effects of intra-amniotic IGF1 therapy on adult body composition, glucose-insulin axis function, and adrenergic sensitivity could indicate improved metabolic regulation during young adulthood in female FGR sheep.

Why Should Growth Hormone (GH) Be Considered a Promising Therapeutic Agent for Arteriogenesis? Insights from the GHAS Trial

Despite the important role that the growth hormone (GH)/IGF-I axis plays in vascular homeostasis, these kind of growth factors barely appear in articles addressing the neovascularization process. Currently, the vascular endothelium is considered as an authentic gland of internal secretion due to the wide variety of released factors and functions with local effects, including the paracrine/autocrine production of GH or IGF-I, for which the endothelium has specific receptors. In this comprehensive review, the evidence involving these proangiogenic hormones in arteriogenesis dealing with the arterial occlusion and making of them a potential therapy is described. All the elements that trigger the local and systemic production of GH/IGF-I, as well as their possible roles both in physiological and pathological conditions are analyzed. All of the evidence is combined with important data from the GHAS trial, in which GH or a placebo were administrated to patients suffering from critical limb ischemia with no option for revascularization. We postulate that GH, alone or in combination, should be considered as a promising therapeutic agent for helping in the approach of ischemic disease.

In early pubertal boys, testosterone and LH are associated with improved anti-oxidation during an aerobic exercise bout

PURPOSE

To investigate the association of the hypothalamic-pituitary-testicular (HPT) axis with pro- and anti- oxidation, in relation to puberty and obesity in boys, before and after an aerobic exercise bout.

METHODS

This is a cross-sectional human observational study of 92 healthy normal-weight, obese pre- and early- pubertal boys that underwent a blood sampling, before, and after an aerobic exercise bout at 70% VO₂max, until exhaustion. LH, FSH, total testosterone (tT) and markers of pro- (TBARS and PCs) and anti- (GSH, GSSG, GPX, catalase, TAC) oxidation were measured.

RESULTS

Baseline LH, FSH, and tT concentrations were greater in early, than in pre- pubertal boys, independently of weight status. Post-exercise, LH concentrations decreased in early pubertal boys while FSH concentrations did not change in any of the studied groups. Baseline and post-exercise tT concentrations were lower in obese than in normal-weight early pubertal boys, while baseline and post-exercise LH and FSH concentrations did not differ between these groups. Post-exercise tT concentrations increased in early pubertal obese boys. Baseline LH, FSH and tT concentrations correlated positively with baseline anti-oxidation markers concentrations in pre-pubertal boys. Baseline tT concentrations correlated positively with the increase of TAC concentrations in early pubertal normal-weight boys. In all boys, baseline LH concentrations were the best positive predictors for the exercise-associated increase of TAC concentrations.

CONCLUSIONS

It appears that the HPT axis maturation during puberty (in particular its LH and testosterone components) is positively associated with the increase of anti-oxidation during a bout of aerobic exercise.

Stress, strain, and pregnancy outcome in postpartum cows

Stress affects the productivity and fertility of cattle. Stress causes strain and individual animals experience different amounts of strain in response to the same amount of stress. The amount of strain determines the impact of stress on fertility. Typical stresses experienced by cattle include environmental, disease, production, nutritional, and psychological. The effect of stress on the reproductive system is mediated by body temperature (heat stress), energy metabolites and metabolic hormones (production and nutritional stresses), the functionality of the hypothalamus-pituitary-gonadal (HPG) axis and (or) the activation of the hypothalamus-pituitary-adrenal (HPA) axis. The strain that occurs in response to stress affects uterine health, oocyte quality, ovarian function, and the developmental capacity of the conceptus. Cows that have less strain in response to a given stress will be more fertile. The goal for future management and genetic selection in farm animals is to reduce production stress, manage the remaining strain, and genetically select cattle with minimal strain in response to stress.

Pregnancy Hypertension and a Commonly Inherited IGF1R Variant (rs2016347) Reduce Breast Cancer Risk by Enhancing Mammary Gland Involution

Background

Terminal duct lobular units (TDLUs) are the anatomic sites of breast cancer initiation, and breast tissue involution resulting in lower TDLU counts has been associated with decreased breast cancer risk. The insulin-like growth factor (IGF) pathway plays a role in breast involution, and systemic changes in this developmental pathway occur with hypertensive disorders of pregnancy (HDP), which have also been associated with lower breast cancer risk, especially in women carrying a functional variant of IGF1R SNP rs2016347. We proposed that this breast cancer protective effect might be explained by increased breast tissue involution.

Materials and Methods

We conducted a retrospective cohort study utilizing the Komen Tissue Bank, which collects breast tissue core biopsies from women without a history of breast cancer. Eighty white non-Hispanic women with a history of HDP were selected along with 120 nonexposed participants, and after genotyping for rs2016347, TDLU parameters were histologically measured blinded to participant characteristics from fixed biopsy sections.

Results

Stratified models by HDP status demonstrated that among HDP+ participants, those carrying two T alleles of rs2016347 had a decrease in TDLU counts of 53.2% when compared to those with no T alleles (p=0.049). Trend analysis demonstrated a multiplicative decrease in counts of 31.6% per T allele (p=0.050). Although no statistically significant interaction was seen between HDP status and T alleles, interaction terms showed increasingly negative values reaching a p value of 0.124 for HDP × 2T alleles.

Conclusions

The observed statistically significant decrease in TDLU counts signifies increased breast epithelial involution in women with prior HDP who inherited the TT genotype of IGF1R SNP rs2016347. The increasing degree of breast involution with greater rs2016347 T allele copy number is consistent with the known progressive reduction in IGF1R expression in breast and other normal tissues.

Aromatized Estrogens Amplify Nocturnal Growth Hormone Secretion in Testosterone-Replaced Older Hypogonadal Men

CONTEXT

Testosterone (T) increases GH secretion in older men with a relative lack of T, in hypogonadal men of all ages, and in patients undergoing sex reassignment. The role of estradiol (E2) in men is less well defined.

OBJECTIVE

To assess the contribution of aromatization of T to spontaneous nocturnal and stimulated GH secretion.

PARTICIPANTS

Four groups of healthy older men (N = 74, age range 57 to 77 years) were studied. The gonadotropic axis was clamped with the gonadotropin-releasing hormone antagonist degarelix. Three groups received T and one group placebo addback. Two T-replaced groups were treated with anastrozole (an aromatase inhibitor) and either placebo or E2 addback.

MAIN OUTCOME MEASURES

Ten-minute GH concentration profiles were quantified by deconvolution analysis, after overnight (2200 to 0800 hours) sampling, and after combined IV injection of GHRH (0.3 µg/kg) and GHRH-2 (0.3 µg/kg) and withdrawal of a 2-hour somatostatin infusion (1 µg/kg/h).

RESULTS

E2 addback during aromatase inhibition increased basal (P = 0.046), pulsatile (P = 0.020), and total (P = 0.018) GH secretion by 60% to 70%. E2 did not potentiate GH secretory stimuli. Logarithmically transformed pulsatile GH secretion correlated strongly and positively with concurrent E2 concentrations overall (P = 0.028) and under anastrozole treatment (P = 0.005).

CONCLUSION

E2 administration in older men transdermally stimulates overnight pulsatile GH secretion. The exact site of E2 action cannot be ascertained from these experiments but may include hypothalamic loci involved in GH regulation, especially because GH secretagogue effects on somatotrope pituitary cells were not affected.

Associations among IGF-1, IGF2, IGF-1R, IGF-2R, IGFBP-3, insulin genetic polymorphisms and central precocious puberty in girls

BACKGROUND

Insulin and insulin-like growth factor (IGF)-1 coupled with growth hormone helps control timing of sexual maturation. Mutations and variants in multiple genes are associated with development or reduced risk of central precocious puberty (CPP).

METHODS

We assessed single nucleotide polymorphisms (SNPs) in the IGF-1, IGF-2, IGF-3, IGF-1 receptor (IGF1R), IGF-2 receptor (IGF2R), and IGF -binding protein 3 (IGFBP-3) genes, and their association with demographics and metabolic proteins in girls with CPP. Z-scores of height, weight, and body mass index (BMI) were calculated with the WHO reference growth standards for children.

RESULTS

IGF-1 serum levels of CPP group exhibited a higher correlation with bone age, z-scores of height and weight, and luteinizing hormone (LH) than those of control group, regardless of BMI adjustment. In the CPP group, height was associated with IGF-2(3580), an adenine to guanine (A/G) SNP at position + 3580. BMI in the CPP group was associated with IGF-2(3580), IGF1R, and the combinations of [IGF-2(3580) + IGF2R], and [IGF-2(3580) + IGFBP-3]. Body weight in the CPP group was associated with the combination of [IGF-2(3580) + IGFBP-3] (p = 0.024). Weight and BMI were significantly associated with the combination of [IGF-2(3580) + IGF2R + IGFBP-3] in the CPP group. These associations were not significantly associated with z-scores of weight, height, or BMI. The distribution of these genotypes, haplotypes, and allele frequencies were similar between control and CPP groups.

CONCLUSIONS

These known SNPs of these IGF-1 axis genes appear to play minor roles in the risk for development of CPP.

Sex-specific changes in postnatal GH and PRL secretion in somatotrope LEPR-null mice

The developing pituitary is a rapidly changing environment that is constantly meeting the physiological demands of the growing organism. During early postnatal development, the anterior pituitary is refining patterns of anterior hormone secretion in response to numerous genetic factors. Our laboratory previously developed a somatotrope leptin receptor (LEPR) deletion mouse model that had decreased lean body mass, disrupted metabolism, decreased GH stores and was GH deficient as an adult. To understand how deletion of LEPR in somatotropes altered GH, we turned our attention to postnatal development. The current study examines GH, PRL, TSH, ACTH, LH and FSH secretion during postnatal days 4, 5, 8, 10 and 15 and compares age and sex differences. The LEPR mutants have dysregulation of GH (P < 0.03) and a reduced developmental prolactin peak in males (P < 0.04) and females (P < 0.002). There were no differences in weight between groups, and the postnatal leptin surge appeared to be normal. Percentages of immunolabeled GH cells were reduced in mutants compared with controls in all age groups by 35-61% in males and 41-44% in females. In addition, we measured pituitary expression of pituitary transcription factors, POU1F1 and PROP1. POU1F1 was reduced in mutant females at PND 10 (P < 0.009) and PND 15 (P < 0.02) but increased in males at PND 10 (P < 0.01). PROP1 was unchanged in female mutants but showed developmental increases at PND 5 (P < 0.02) and PND 15 (P < 0.01). These studies show that the dysfunction caused by LEPR deletion in somatotropes begins as early as neonatal development and involves developing GH and prolactin cells (somatolactotropes).

Neuropeptidome of the Hypothalamus and Pituitary Gland of Indicine × Taurine Heifers: Evidence of Differential Neuropeptide Processing in the Pituitary Gland before and after Puberty

Puberty in cattle is regulated by an endocrine axis, which includes a complex milieu of neuropeptides in the hypothalamus and pituitary gland. The neuropeptidome of hypothalamic-pituitary gland tissue of pre- (PRE) and postpubertal (POST) Bos indicus-influenced heifers was characterized, followed by quantitative analysis of 51 fertility-related neuropeptides in these tissues. Comparison of peptide abundances with gene expression levels allowed assessment of post-transcriptional peptide processing. On the basis of classical cleavage, 124 mature neuropeptides from 35 precursor proteins were detected in hypothalamus and pituitary gland tissues of three PRE and three POST Brangus heifers. An additional 19 peptides (cerebellins, PEN peptides) previously reported as neuropeptides that did not follow classical cleavage were also identified. In the pre-pubertal hypothalamus, a greater diversity of neuropeptides (25.8%) was identified relative to post-pubertal heifers, while in the pituitary gland, 38.6% more neuropeptides were detected in the post-pubertal heifers. Neuro-tissues of PRE and POST heifers revealed abundance differences ( p < 0.05) in peptides from protein precursors involved in packaging and processing (e.g., the granin family and ProSAAS) or neuron stimulation (PENK, CART, POMC, cerebellins). On their own, the transcriptome data of the precursor genes could not predict the neuropeptide profile in the exact same tissues in several cases. This provides further evidence of the importance of differential processing of the neuropeptide precursors in the pituitary before and after puberty.

Species Comparison of Postnatal Development of the Female Reproductive System

The postnatal development of the female reproductive system in laboratory animals and humans is reviewed. To enable a meaningful species comparison of the developing female reproductive system, common definitions of developmental processes were established with a focus made on aspects that are similar across species. A species comparison of the key endocrine, morphologic, and functional (onset of ovarian cycles and ability to reproduce) features of postnatal development of the female reproductive system is provided for human, nonhuman primate, dog, rat, and also mouse, minipig, and rabbit where possible. Species differences in the timing and control of female sexual maturation are highlighted. Additionally, a species comparison of the type and timing of female reproductive ovarian cycles was compiled. Human development provided the frame of reference, and then other common laboratory species were compared. The comparison has inherent challenges because the processes involved and sequence of events can differ greatly across species. Broad strokes were taken to assign a particular average age to an event and are to be used with caution. Methods of evaluation of postnatal female reproductive development in laboratory animals are discussed. Lastly, control rodent data from one of the author's laboratory on vaginal opening, first estrus, estrous cyclicity, and the histopathology involved with the developing female rat and mouse are presented. The information provided in this review is intended to be a resource for the design and interpretation of juvenile animal toxicity testing and ultimately, the relevance of the data to characterize potential risks for women and girls. Birth Defects Research 110:163-189, 2018. © 2017 Wiley Periodicals, Inc.

Premenstrual Dysphoric Disorder Symptoms Following Ovarian Suppression: Triggered by Change in Ovarian Steroid Levels But Not Continuous Stable Levels

OBJECTIVE

Premenstrual dysphoric disorder (PMDD) symptoms are eliminated by ovarian suppression and stimulated by administration of ovarian steroids, yet they appear with ovarian steroid levels indistinguishable from those in women without PMDD. Thus, symptoms could be precipitated either by an acute change in ovarian steroid levels or by stable levels above a critical threshold playing a permissive role in expression of an underlying infradian affective "pacemaker." The authors attempted to determine which condition triggers PMDD symptoms.

METHOD

The study included 22 women with PMDD, ages 30 to 50 years. Twelve women who experienced symptom remission after 2-3 months of GnRH agonist-induced ovarian suppression (leuprolide) then received 1 month of single-blind (participant only) placebo and then 3 months of continuous combined estradiol/progesterone. Primary outcome measures were the Rating for Premenstrual Tension observer and self-ratings completed every 2 weeks during clinic visits. Multivariate repeated-measure ANOVA for mixed models was employed.

RESULTS

Both self- and observer-rated scores on the Rating for Premenstrual Tension were significantly increased (more symptomatic) during the first month of combined estradiol/progesterone compared with the last month of leuprolide alone, the placebo month, and the second and third months of estradiol/progesterone. There were no significant differences in symptom severity between the last month of leuprolide alone, placebo month, or second and third months of estradiol/progesterone. Finally, the Rating for Premenstrual Tension scores in the second and third estradiol/progesterone months did not significantly differ.

CONCLUSIONS

The findings demonstrate that the change in estradiol/progesterone levels from low to high, and not the steady-state level, was associated with onset of PMDD symptoms. Therapeutic efforts to modulate the change in steroid levels proximate to ovulation merit further study.

A time-varying biased random walk approach to human growth

Growth and development are dominated by gene-environment interactions. Many approaches have been proposed to model growth, but most are either descriptive or describe population level phenomena. We present a random walk-based growth model capable of predicting individual height, in which the growth increments are taken from time varying distributions mimicking the bursting behaviour of observed saltatory growth. We derive analytic equations and also develop a computational model of such growth that takes into account gene-environment interactions. Using an independent prospective birth cohort study of 190 infants, we predict height at 6 years of age. In a subset of 27 subjects, we adaptively train the model to account for growth between birth and 1 year of age using a Bayesian approach. The 5-year predicted heights compare well with actual data (measured height = 0.838*predicted height + 18.3; R² = 0.51) with an average error of 3.3%. In one patient, we also exemplify how our growth prediction model can be used for the early detection of growth deficiency and the evaluation of the effectiveness of growth hormone therapy.

Predictors of Insulin-Like Growth Factor-I Responses to Growth Hormone Replacement in Young Adults with Growth Hormone Deficiency

BACKGROUND/AIMS

Physiological growth hormone (GH) secretion and insulin-like growth factor-I (IGF-I) levels are greater in young compared to older adults. We evaluated IGF-I levels and predictors of IGF-I responses in young adults on GH replacement.

DESIGN

From the KIMS database, 310 young adults (age 15-26 years) with severe GH deficiency related to childhood-onset disease and commenced on 'adult GH replacement' were identified. 'IGF-I responses' were estimated from first-year increments in IGF-I standard deviation scores (SDS) and adjusted for GH dose. Body composition was assessed by bioimpedance in 143 patients.

RESULTS

IGF-I levels increased markedly from baseline to 1 year of replacement (-3.75 ± 1.94 vs. -1.36 ± 1.86 SDS, p < 0.0001), but remained low compared to normative data despite dose titration. In multivariate models, IGF-I responses were positively associated with age [B (SE) SDS/(mg/m2); 0.52 (0.15), p = 0.0007] and BMI SDS [1.06 (0.25), p < 0.0001] and inversely associated with female gender [-4.45 (0.79), p < 0.0001] and baseline IGF-I SDS [-1.44 (0.20), p < 0.0001]. IGF-I responses were positively associated with first-year increases in lean body mass (r = 0.19, p = 0.003) and haemoglobin A1c (r = 0.15, p = 0.031).

CONCLUSIONS

Low IGF-I levels in young adults on treatment may reflect suboptimal GH replacement. Identification of predictors for IGF-I responses could lead to a more appropriate replacement strategy. Association between IGF-I responses and lean body mass suggests that maintaining age-appropriate IGF-I levels is important during therapy.

A summary of the influence of exogenous estrogen administration across the lifespan on the GH/IGF-1 axis and implications for bone health

Bone growth, development, and remodeling are modulated by numerous circulating hormones. Throughout the lifespan, the extent to which each of the hormones impacts bone differs. Understanding the independent and combined impact of these hormones on controlling bone remodeling allows for the development of more informed decision making regarding pharmacology, specifically the use of hormonal medication, at all ages. Endocrine control of bone health in women is largely dictated by the growth hormone (GH)/insulin-like growth factor-1 (IGF-1) axis and the hypothalamic-pituitary-ovarian (HPO) axis. Growth hormone, secreted from the pituitary gland, stimulates cells in almost every tissue to secrete IGF-1, although the majority of circulating IGF-1 is produced hepatically. Indeed, systemic IGF-1 concentrations have been found to be correlated with bone mineral density (BMD) in both pre- and post-menopausal women and is often used as a marker of bone formation. Sex steroids produced by the ovaries, namely estradiol, mediate bone resorption through binding to estrogen receptors on osteoclasts and osteoblasts. Specifically, by increasing osteoclast apoptosis and decreasing osteoblast apoptosis, adequate estrogen levels prevent excessive bone resorption, which helps to explain the rapid decline in bone mass that occurs with the menopausal decrease in estrogen production. Though there are documented correlations between endogenous estrogen concentrations and GH/IGF-1 dynamics, this relationship changes across the lifespan as sex-steroid dynamics fluctuate and, possibly, as tissue responsiveness to GH stimulation decreases. Aside from the known role of endogenous sex steroids on bone health, the impact of exogenous estrogen administration is of interest, as exogenous formulations further modulate GH and IGF-1 production. However, the effect and extent of GH and IGF-1 modulation seems to be largely dependent on age at administration and route of administration. Specifically, premenopausal women using combined oral contraceptive therapy (COC), post-menopausal women taking oral hormone therapy (HT), and both pre- and post-menopausal women using a transdermal form of estrogen therapy (COC or HT) demonstrate disparate GH/IGF-1 responses to exogenous estrogen. This review serves to summarize what is currently known regarding the influence of exogenous estrogen administration across the lifespan on the GH/IGF-1 axis and implications for bone health.

Prenatal and postnatal mothering by diesel exhaust PM2.5-exposed dams differentially program mouse energy metabolism

BACKGROUND

Obesity is one of the leading threats to global public health. It is consequent to abnormal energy metabolism. Currently, it has been well established that maternal exposure to environmental stressors that cause inappropriate fetal development may have long-term adverse effects on offspring energy metabolism in an exposure timing-dependent manner, known as developmental programming of health and diseases paradigm. Rapidly increasing evidence has indicated that maternal exposure to ambient fine particles (PM2.5) correlates to abnormal fetal development. In the present study, we therefore assessed whether maternal exposure to diesel exhaust PM2.5 (DEP), the major component of ambient PM2.5 in urban areas, programs offspring energy metabolism, and further examined how the timing of exposure impacts this programming.

RESULTS

The growth trajectory of offspring shows that although prenatal maternal exposure to DEP did not impact the birth weight of offspring, it significantly decreased offspring body weight from postnatal week 2 until the end of observation. This weight loss effect of prenatal maternal exposure to DEP coincided with decreased food intake but not alteration in brown adipose tissue (BAT) morphology. The hypophagic effect of prenatal maternal exposure to DEP was in concord with decreased hypothalamic expression of an orexigenic peptide NPY, suggesting that the prenatal maternal exposure to DEP impacts offspring energy balance primarily through programming of food intake. Paradoxically, the reduced body weight resulted from prenatal maternal exposure to DEP was accompanied by increased mass of epididymal adipose tissue, which was due to hyperplasia as morphological analysis did not observe any hypertrophy. In direct contrast, the postnatal mothering by DEP-exposed dams increased offspring body weight during lactation and adulthood, paralleled by markedly increased fat accumulation and decreased UCP1 expression in BAT but not alteration in food intake. The weight gain induced by postnatal mothering by DEP-exposed dams was also expressed as an increased adiposity. But it concurred with a marked hypertrophy of adipocytes.

CONCLUSION

Prenatal and postnatal mothering by DEP-exposed dams differentially program offspring energy metabolism, underscoring consideration of the exposure timing when examining the adverse effects of maternal exposure to ambient PM2.5.

Exercise-Induced Oxidative Stress Responses in the Pediatric Population

Adults demonstrate an upregulation of their pro- and anti-oxidant mechanisms in response to acute exercise while systematic exercise training enhances their antioxidant capacity, thereby leading to a reduced generation of free radicals both at rest and in response to exercise stress. However, less information exists regarding oxidative stress responses and the underlying mechanisms in the pediatric population. Evidence suggests that exercise-induced redox perturbations may be valuable in order to monitor exercise-induced inflammatory responses and as such training overload in children and adolescents as well as monitor optimal growth and development. The purpose of this review was to provide an update on oxidative stress responses to acute and chronic exercise in youth. It has been documented that acute exercise induces age-specific transient alterations in both oxidant and antioxidant markers in children and adolescents. However, these responses seem to be affected by factors such as training phase, training load, fitness level, mode of exercise etc. In relation to chronic adaptation, the role of training on oxidative stress adaptation has not been adequately investigated. The two studies performed so far indicate that children and adolescents exhibit positive adaptations of their antioxidant system, as adults do. More studies are needed in order to shed light on oxidative stress and antioxidant responses, following acute exercise and training adaptations in youth. Available evidence suggests that small amounts of oxidative stress may be necessary for growth whereas the transition to adolescence from childhood may promote maturation of pro- and anti-oxidant mechanisms. Available evidence also suggests that obesity may negatively affect basal and exercise-related antioxidant responses in the peripubertal period during pre- and early-puberty.

Pulsatility of Hypothalamo-Pituitary Hormones: A Challenge in Quantification

Neuroendocrine systems control many of the most fundamental physiological processes, e.g., reproduction, growth, adaptations to stress, and metabolism. Each such system involves the hypothalamus, the pituitary, and a specific target gland or organ. In the quantification of the interactions among these components, biostatistical modeling has played an important role. In the present article, five key challenges to an understanding of the interactions of these systems are illustrated and discussed critically.

Endogenous Estrogen Regulates Somatostatin-Induced Rebound GH Secretion in Postmenopausal Women

BACKGROUND

Systemic concentrations of T, estradiol (E₂), GH, IGF-1, and IGF binding protein-3 decline in healthy aging individuals. Conversely, T and E₂ stimulate GH and IGF-1 production in hypogonadal patients.

HYPOTHESIS

Because E₂ stimulates GH secretion, putatively via the nuclear estrogen receptor-α and E₂ and GH fall with menopause, we postulated that diminished endogenous E₂ contributes to low GH output in older women.

LOCATION

The study was conducted at the Mayo Center for Clinical and Translational Science.

STUDY DESIGN

This was a randomized, double-blind, controlled study in 60 healthy postmenopausal women treated with the following: 1) double placebo; 2) anastrozole, a potent inhibitor of aromatase-enzyme activity, which mediates E₂ synthesis from T; and/or 3) fulvestrant, a selective estrogen receptor-α antagonist.

METHODS

GH pulse generation was quantified by frequent GH sampling before and after short-term iv somatostatin infusion, thought to induce hypothalamic GHRH-mediated rebound-like GH secretion.

RESULTS

On anastrozole, E₂ fell from 3.1 ± 0.35 pg/mL to 0.36 ± 0.04 pg/mL, and estrone from 13 ± 1.4 pg/mL to 1.9 ± 0.01 pg/mL (P < .001) by mass spectrometry. Estrogen values were unchanged by fulvestrant. T concentrations did not change. One-hour peak GH rebound after somatostatin infusion declined markedly during both estrogen-deprivation schedules (P < .001). Mean (150 min) maximal GH rebound decreased comparably (P < .001). Measures of GH rebound correlated negatively with computed tomography-estimated abdominal visceral fat (all P < .05).

CONCLUSION

These data suggest a previously unrecognized dependence of hypothalamo-pituitary GH regulation on low levels of endogenous estrogen after menopause.

A Sex-Dependent, Tropic Role for Leptin in the Somatotrope as a Regulator of POU1F1 and POU1F1-Dependent Hormones

Pituitary somatotropes perform the key function of coordinating organismic growth and body composition with metabolic signals. However, the mechanism by which they sense and respond to metabolic signals via the adipokine leptin is unknown. The complex interplay between the heterogeneous cell types of the pituitary confounds the identification of somatotrope-specific mechanisms. Somatotropes represent 30%-40% of the anterior pituitary population and are derived from a lineage of cells that are activated by the Pit-Oct-Unc domain family domain class 1 transcription factor 1 (POU1F1) to produce GH, prolactin (PRL). and TSH. To determine the mechanism by which leptin controls somatotrope function, we used Cre-LoxP technology and fluorescence-activated cell sorting to purify and study control or leptin receptor-deleted (Lepr null) somatotropes. We report that Lepr-null somatotropes show significant reductions in GH protein (GH) and Gh mRNA. By contrast, enzyme immunoassays detected no changes in ACTH, LH, and FSH levels in mutants, indicating that the control of these hormones is independent of leptin signaling to somatotropes. Reduced TSH and PRL levels were also observed, but interestingly, this reduction occurred only in in Lepr-null somatotropes from mutant females and not from males. Consistent with the sex-specific reduction in Gh mRNA, TSH, and PRL, enzyme immunoassays detected a sex-specific reduction in POU1F1 protein levels in adult female Lepr-null somatotropes. Collectively, this study of purified Lepr-null somatotropes has uncovered an unexpected tropic role for leptin in the control of POU1F1 and all POU1F1-dependent hormones. This supports a broader role for somatotropes as metabolic sensors including sex-specific responses to leptin.

Transient Postnatal Gonadal Activation and Growth Velocity in Infancy

BACKGROUND AND OBJECTIVE

Transient activation of the hypothalamic-pituitary-gonadal axis with a sex steroid surge is observed in boys and girls during the first months of life. However, the role of sex steroids in the regulation of growth has not been substantiated in infancy. We tested the hypothesis that testosterone (T) surge, known to be higher in infant boys than in girls during the transient postnatal gonadal activation regulates linear growth in infants.

METHODS

To characterize in detail the linear growth velocity (GV) differences between genders in the normal population in early infancy, we evaluated growth of 18 570 healthy infants (51.0% boys) with 162 003 height measurements from birth to 12 months of age. GV was monitored and compared with serially measured urinary T and estradiol levels and serum insulin-like growth factor 1 levels in 84 healthy infants (45% boys) during the first 6 months of life.

RESULTS

GV was significantly faster from birth to 6 months of age in boys than in girls (P ≤ .01). The greatest GV difference, 4.1 cm per year, was observed at 1 month of age, simultaneously with the peak of postnatal gonadal activation. In the mixed model analysis, GV showed a significant positive association with T in both genders (parameter estimate up to 0.62, 95% confidence interval 0.44-0.81).

CONCLUSIONS

These results provide a new insight into the regulation of growth in infants and elucidate a novel biological role of the transient postnatal gonadal activation in growth regulation.

Organochlorine pesticides and female puberty in South Kazakhstan

The purpose of the study was to assess the puberty of females living in cotton-growing regions of South Kazakhstan, where organochlorine pesticides are widely used. The physical growth and sexual development were assessed; organochlorine pesticides, gonadotropic and steroid hormones, as well as insulin-like growth factor 1 in the peripheral blood were determined. 524 females (adolescents aged 10-17) were examined. They were divided into 2 groups, depending on their place of residence. The clinical research included the assessment of physical and sexual development. All examined females lived in rural areas, i.e. they were comparable in terms of social, welfare, and climatographic factors. A high concentration of organochlorine pesticides (lindane-18.51±0.16mg/l, dieldrin-169.16±3.13mg/l, DDT-177.78±2.71mg/l, endrin-37.57±0.9mg/l) in the blood of females living in regions exposed to pesticides compared to their peers (4.05±0.41mg/l, 30.8±3.7mg/l, 109.7±2.58mg/l, 4.85±0.69mg/l respectively) was found (p<0.001). The physical and sexual development of such females was delayed. The research established a correlation between the concentration of pesticides and the endocrine status, as well as with the insulin-like growth factor 1. This shows the adverse effect of organochlorine pesticides on the development of the female reproductive system during puberty.

Birth Size, Early Life Weight Gain, and Midchildhood Cardiometabolic Health

OBJECTIVE

To examine associations of birth size and weight gain during 4 early-life age intervals with midchildhood adiposity and metabolic profile and to evaluate for an interaction between birth size and early-life weight gain.

STUDY DESIGN

Using data from 963 participants of Project Viva, a US prebirth cohort, we used multivariable linear regression to examine relations of birth size (tertiles of birthweight-for-gestational-age z-score) and weight gain (body mass index z-score [BMIZ] change) during 4 age intervals (birth-6 months, 6 months-1 year, 1-2 years, 2-3 years) with body composition and metabolic biomarkers during midchildhood (6.6-10.7 years).

RESULTS

After accounting for confounders and previous growth, greater BMIZ change during all 4 age intervals corresponded with higher midchildhood adiposity, with larger effect sizes for later (1-2 years and 2-3 years) vs earlier (birth-6 months and 6 months-1 year) time frames. We observed effect modification by birth size for the birth-6 months and 6 months-1 year intervals. Greater birth-6 months BMIZ change was associated with higher overall adiposity (0.40 [95% CI 0.29, 0.51] kg dual x-ray absorptiometry total fat mass per z-score) among children in the highest birth size tertile. Similar associations were observed for central adiposity. Each increment in 6 months-1 year BMIZ change corresponded with 0.55 (0.05, 1.05) units higher homeostatic model assessment of insulin resistance and 2.68 (0.96, 4.40) ng/mL higher leptin among the smallest infants.

CONCLUSIONS

BMIZ gain after 1 year is associated with greater midchildhood adiposity regardless of birth size, whereas the long-term influence of weight gain during the first postnatal year may depend on size at birth. Future studies are warranted to validate findings and examine relations with conventional birth size cut-offs.

Neuroendocrine Regulation of Growth Hormone Secretion

This article reviews the main findings that emerged in the intervening years since the previous volume on hormonal control of growth in the section on the endocrine system of the Handbook of Physiology concerning the intra- and extrahypothalamic neuronal networks connecting growth hormone releasing hormone (GHRH) and somatostatin hypophysiotropic neurons and the integration between regulators of food intake/metabolism and GH release. Among these findings, the discovery of ghrelin still raises many unanswered questions. One important event was the application of deconvolution analysis to the pulsatile patterns of GH secretion in different mammalian species, including Man, according to gender, hormonal environment and ageing. Concerning this last phenomenon, a great body of evidence now supports the role of an attenuation of the GHRH/GH/Insulin-like growth factor-1 (IGF-1) axis in the control of mammalian aging.

A 3-day high-fat/low-carbohydrate diet does not alter exercise-induced growth hormone response in healthy males

OBJECTIVE

The purpose of the present study was to examine the effects of 3 days isoenergetic high-fat/low-carbohydrate diet (HF-LC) relative to low-fat/high-carbohydrate diet (LF-HC) on the exercise-induced growth hormone (GH) response in healthy male subjects.

DESIGN

Ten healthy young males participated in this study. Each subject consumed the HF-LC (18±1% protein, 61±2% fat, 21±1% carbohydrate, 2720 kcal per day) for 3 consecutive days after consuming the LF-HC (18±1% protein, 20±1% fat, 62±1% carbohydrate, 2755 kcal per day) for 3 consecutive days. After each dietary intervention period, the hormonal and metabolic responses to an acute exercise (30 min of continuous pedaling at 60% of V˙O2max) were compared. The intramyocellular lipid (IMCL) contents in the vastus lateralis, soleus, and tibialis anterior were evaluated by proton magnetic resonance spectroscopy.

RESULTS

Serum GH concentrations increased significantly during the exercise after both the HF-LC and LF-HC periods (P<0.05). However, the exercise-induced GH response was not significantly different between the two periods. Fat utilization and lipolytic responses during the exercise were enhanced significantly after the HF-LC period compared with the LF-HC period. IMCL content did not differ significantly in any portion of muscle after the dietary interventions.

CONCLUSIONS

We could not show that short-term HF-LC consumption changed significantly exercise-induced GH response or IMCL content in healthy young males.

Developmental influences on circuits programming susceptibility to obesity

Suboptimal maternal nutrition exerts lasting impacts on obesity risk in offspring, but the direction of the effect is determined by the timing of exposure. While maternal undernutrition in early pregnancy is associated with increased body mass index, in later pregnancy it can be protective. The importance of the timing of maternal undernutrition is also observed in rodents, however, many of the processes that occur in the last trimester of human gestation are delayed to the postnatal period. Neonatal leptin administration exerts lasting impacts on susceptibility to obesity in rodents. Although leptin can influence the formation of hypothalamic circuits involved in homeostatic control of feeding during the postnatal period, these effects are too late to account for its ability to reverse adverse metabolic programming due to early gestational exposure to maternal undernutrition. This review presents an alternative framework for understanding the effects of neonatal leptin through influences on developing thermoregulatory circuits.

Sex Differences in Somatotrope Dependency on Leptin Receptors in Young Mice: Ablation of LEPR Causes Severe Growth Hormone Deficiency and Abdominal Obesity in Males

Leptin receptor (LEPR) signaling controls appetite and energy expenditure. Somatotrope-specific deletion of the LEPRb signaling isoform causes GH deficiency and obesity. The present study selectively ablated Lepr exon 1 in somatotropes, which removes the signal peptide, causing the loss of all isoforms of LEPR. Excision of Lepr exon 1 was restricted to the pituitary, and mutant somatotropes failed to respond to leptin. Young (2-3 mo) males showed a severe 84% reduction in serum GH levels and more than 60% reduction in immunolabeled GH cells compared with 41%-42% reductions in GH and GH cells in mutant females. Mutant males (35 d) and females (45 d) weighed less than controls and males had lower lean body mass. Image analysis of adipose tissue by magnetic resonance imaging showed that young males had a 2-fold increase in abdominal fat mass and increased adipose tissue density. Young females had only an overall increase in adipose tissue. Both males and females showed lower energy expenditure and higher respiratory quotient, indicating preferential carbohydrate burning. Young mutant males slept less and were more restless during the dark phase, whereas the opposite was true of females. The effects of a Cre-bearing sire on his non-Cre-recombinase bearing progeny are seen by increased respiratory quotient and reduced litter sizes. These studies elucidate clear sex differences in the extent to which somatotropes are dependent on all isoforms of LEPR. These results, which were not seen with the ablation of Lepr exon 17, highlight the severe consequences of ablation of LEPR in male somatotropes.

Multipathway modulation of exercise and glucose stress effects upon GH secretion in healthy men

OBJECTIVE

Exercise evokes pulsatile GH release followed by autonegative feedback, whereas glucose suppresses GH release followed by rebound-like GH release (feedforward escape). Here we test the hypothesis that age, sex steroids, insulin, body composition and physical power jointly determine these dynamic GH responses.

METHODS

This was a prospectively randomized glucose-blinded study conducted in the Mayo Center for Advancing Translational Sciences in healthy men ages 19-77 years (N=23). Three conditions, fasting/rest/saline, fasting/exercise/saline and fasting/rest/iv glucose infusions, were used to drive GH dynamics during 10-min blood sampling for 6h. Linear correlation analysis was applied to relate peak/nadir GH dynamics to age, sex steroids, insulin, CT-estimated abdominal fat and physical power (work per unit time).

RESULTS

Compared with the fasting/rest/saline (control) day, fasting/exercise/saline infusion evoked peak GH within 1h, followed by negative feedback 3-5h later. The dynamic GH excursion was strongly (R(2)=0.634) influenced by (i) insulin negatively (P=0.011), (ii) power positively (P=0.0008), and (iii) E2 positively (P=0.001). Dynamic glucose-modulated GH release was determined by insulin negatively (P=0.0039) and power positively (P=0.0034) (R(2)=0.454). Under rest/saline, power (P=0.031) and total abdominal fat (P=0.012) (R(2)=0.267) were the dominant correlates of GH excursions.

CONCLUSION

In healthy men, dynamic GH perturbations induced by exercise and glucose are strongly related to physical power, insulin, estradiol, and body composition, thus suggesting a network of regulatory pathways.

Antioxidation improves in puberty in normal weight and obese boys, in positive association with exercise-stimulated growth hormone secretion

BACKGROUND

Oxidative stress is associated with obesity while the evidence for the role of GH in pro- and antioxidation is inconclusive. This study investigates the relationships between growth hormone (GH), pro- and antioxidation in relation to obesity and puberty before and after an acute bout of exercise.

METHODS

In this case-control study, 76 healthy normal-weight and obese, prepubertal and pubertal boys underwent a blood sampling before and immediately after an aerobic exercise bout until exhaustion at 70% maximal oxygen consumption. Markers of prooxidation (thiobarbituric acid reactive substances (TBARS) and protein carbonyls (PCs)) and antioxidation (glutathione (GSH), oxidized glutathione disulfide (GSSG), GSH/GSSG ratio, glutathione peroxidase (GPX), catalase, and total antioxidant capacity (TAC)) and hormones (GH, insulin-like growth factor (IGF)-1, IGF-BP-3, luteinizing hormone, follicle-stimulating hormone, and testosterone) were measured.

RESULTS

Baseline and postexercise TBARS and PCs were greater, while baseline GSH, GSH/GSSG ratio, GPX, and TAC were lower in obese than that in normal-weight participants. In all participants, waist was the best negative and positive predictor for postexercise GPX and TBARS, respectively. Baseline TAC was greater in pubertal than that in pre-pubertal participants. In all participants, baseline GH was the best negative predictor for postexercise PCs. Significant positive linear correlation exists between the exercise-associated GH, and GSSG increases in pubertal normal-weight boys.

CONCLUSIONS

Higher prooxidation and lower antioxidation were observed in obese boys, while antioxidation improves with puberty and postexercise, paralleling GH accentuated secretion.

Age-related responses in circulating markers of redox status in healthy adolescents and adults during the course of a training macrocycle

Redox status changes during an annual training cycle in young and adult track and field athletes and possible differences between the two age groups were assessed. Forty-six individuals (24 children and 22 adults) were assigned to four groups: trained adolescents, (TAD, N = 13), untrained adolescents (UAD, N = 11), trained adults (TA, N = 12), and untrained adults (UA, N = 10). Aerobic capacity and redox status related variables [total antioxidant capacity (TAC), glutathione (GSH), catalase activity, TBARS, protein carbonyls (PC), uric acid, and bilirubin] were assessed at rest and in response to a time-trial bout before training, at mid- and posttraining. TAC, catalase activity, TBARS, PC, uric acid, and bilirubin increased and GSH declined in all groups in response to acute exercise independent of training status and age. Training improved aerobic capacity, TAC, and GSH at rest and in response to exercise. Age affected basal and exercise-induced responses since adults demonstrated a greater TAC and GSH levels at rest and a greater rise of TBARS, protein carbonyls, and TAC and decline of GSH in response to exercise. Catalase activity, uric acid, and bilirubin responses were comparable among groups. These results suggest that acute exercise, age, and training modulate the antioxidant reserves of the body.

Sex-dependent differences in the effect of early weaning on the chosen hormones secretion in sheep during the postnatal transition to puberty – Preliminary results

The influence of early weaning on the cortisol, follicle-stimulating hormone (FSH), luteinizing hormone (LH) and growth hormone (GH) secretion in lambs of both sexes and testosterone (T4) level in male lambs during the postnatal transition to puberty was investigated by radioimmunoassay. It was hypothesized that this influence is long-term and sexually dimorphic. Hence, the effect of weaning at 5 weeks of age in comparison with the weaning at 9 weeks of age on hormone concentrations in peripheral blood plasma of 5-, 9-, 12-, and 16-week-old lambs of both sexes was investigated. The cortisol concentrations were greater (P<0.05) in control and early weaned female lambs than in male lambs at investigated stages. Weaning at 5 weeks of age resulted in the lover (P<0.05) cortisol secretion in male lambs in contrast to the greater (P<0.05) cortisol secretion in female lambs at 16 weeks of age. Weaning at 5 weeks of age stimulated (P<0.001) the FSH secretion, but reduced (P<0.001) the LH, GH and T4 secretion in 16-week-old male lambs. In female lambs early weaning inhibited (P<0.05) the FSH secretion at 9 weeks of age, LH secretion after 9 weeks of age and GH secretion after 12 weeks of age. Thus, early weaning results in the sexually dimorphic stress reaction that is more potent and long-lasting in female in contrast to male lambs. This maternal deprivation stress contributes to the inhibition of LH and GH secretion in lambs of both sexes and T4 secretion in male lambs during the postnatal transition to puberty.