MECHANISMS IN ENDOCRINOLOGY: Paracrine and endocrine control of the growth hormone axis by estrogen

Dual role of pregnancy in breast cancer risk

Reproductive history is one of the strongest risk factors for breast cancer in women. Pregnancy can promote short-term breast cancer risk, but also reduce a woman's lifetime risk of breast cancer. Changes in hormone levels before and after pregnancy are one of the key factors in breast cancer risk. This article summarizes the changes in hormone levels before and after pregnancy, and the roles of hormones in mammary gland development and breast cancer progression. Other factors, such as changes in breast morphology and mammary gland differentiation, changes in the proportion of mammary stem cells (MaSCs), changes in the immune and inflammatory environment, and changes in lactation before and after pregnancy, also play key roles in the occurrence and development of breast cancer. This review discusses the dual effects and the potential mechanisms of pregnancy on breast cancer risk from the above aspects, which is helpful to understand the complexity of female breast cancer occurrence.

DHEA-S, Androstenedione, 17-β-estradiol signature as novel biomarkers for early prediction of risk of malignant pleural mesothelioma linked to asbestos-exposure: A preliminary investigation

17-β-estradiol, involved in mesothelioma pathogenesis, and its precursors were explored as potential biomarkers for the early diagnosis of mesothelioma. Using enzyme-linked immunosorbent assay(ELISA) for 17-β-estradiol and ultra-high performance liquid chromatography/tandem mass spectrometry(UHPLC-MS/MS) for 19 17-β-estradiol precursors, a comprehensive analysis of 20steroid hormones was conducted in the serum of mesothelioma patients(n=67), asbestos-exposed healthy subjects(n=39), and non-asbestos-exposed healthy subjects(n=35). Bioinformatics analysis explored three potential serum biomarkers: 17-β-estradiol, DHEA-S, and androstenedione. The results revealed significant differences in 17-β-estradiol levels between mesothelioma patients and both non-asbestos-exposed and asbestos-exposed healthy subjects. No significant variations in serum 17-β-estradiol levels were observed among mesothelioma patients at different stages, suggesting its potential as an early diagnostic marker. 17-β-estradiol levels were similar in mesothelioma patients with environmental and occupational asbestos exposure, while males with occupational asbestos exposure exhibited significantly higher levels of 17-β-estradiol compared to females. Significant reduction in androstenedione and an increase in DHEA-S were observed in asbestos-exposed individuals compared to non-asbestos-exposed individuals. The analysis of DHEA-S-androstenedione-17-β-estradiol signature score showed an increase in asbestos-exposed individuals and mesothelioma patients compared to non-asbestos-exposed individuals, and this score effectively distinguished between the groups. The Cancer Genome Atlas data was utilized to analyze the expression of 5-α-reductase1 and hydroxysteroid-17β-dehydrogenase2 genes. The findings indicated that mesothelioma patients with elevated gene values for 5-α-reductase1 and hydroxysteroid-17β-dehydrogenase2 have a worse or better prognosis on overall survival, respectively. In conclusion, this study suggests 17-β-estradiol, DHEA-S, and androstenedione as biomarkers for mesothelioma risk and early diagnosis of mesothelioma in asbestos-exposed individuals, aiding timely intervention and improved care.

Growth Hormone Treatment for Non-GHD Disorders: Excitement Tempered by Biology

The success of growth hormone (GH) replacement in children with classical GH deficiency has led to excitement that other causes of short stature may benefit similarly. However, clinical experience has shown less consistent and generally less dramatic effects on adult height, perhaps not surprising in light of increased understanding of GH and growth plate biology. Nonetheless, clinical demand for GH treatment continues to grow. Upon the 20th anniversary of the US Food and Drug Administration's approval of GH treatment for idiopathic short stature, this review will consider the factors underlying the expansion of GH treatment, the biological mechanisms of GH action, the non-GH-deficient uses of GH as a height-promoting agent, biological constraints to GH action, and future directions.

Association of Body Mass Index with Insulin-like Growth Factor-1 Levels among 3227 Chinese Children Aged 2-18 Years

OBJECTIVES

Insulin-like growth factor-1 (IGF-1) levels are affected by nutritional status, yet there is limited research exploring the association between body mass index (BMI) and IGF-1 levels among children.

METHODS

This cross-sectional study included 3227 children aged 2-18 years without specific diseases, whose height, weight, and pubertal stages were measured and assessed by pediatricians. BMI standard deviation scores (BMISDS) were used to categorize children as underweight (BMISDS < -2); normal-weight (-2 ≤ BMISDS ≤ 1); overweight (1 < BMISDS ≤ 2); and obese (BMISDS > 2). Children were divided into low-level (<-0.67 SD) and nonlow-level (≥-0.67 SD) groups based on IGF-1 standard deviation scores (IGF-1SDS). The association between IGF-1 and BMI as categorical and continuous variables was explored by Binary logistic regression, the restrictive cubic spline model, and the generalized additive model. Models were adjusted by height and pubertal development. Recursive algorithm and multivariate piecewise linear regression were further utilized to assess the threshold of the smooth curve.

RESULTS

IGF-1 levels varied by BMI categories, with the highest levels observed in the overweight group. The proportion of low IGF-1 levels in underweight, normal-weight, overweight, and obese groups was 32.1%, 14.2%, 8.4%, and 6.5%, respectively. The risk odds of low IGF-1 levels in underweight children were 2.86-, 2.20-, and 2.25-fold higher than in children with normal weight before adjustment, after adjustment for height, and after adjustment for height and puberty, respectively. When analyzing the association between BMI and low IGF-1 levels, dose-response analysis demonstrated an inverted J-shaped relationship between BMISDS and low IGF-1 levels. Lower or higher BMISDS increased the odds of low IGF-1 levels, and significance was retained in underweight children but not in obese children. When BMI and IGF-1 levels were used as continuous variables, the relationship between the BMISDS and IGF-1SDS followed a nonlinear inverted U shape. IGF-1SDS increased with the increase of BMISDS (β = 0.174, 95% CI: 0.141 to 0.208, p < 0.01) when BMISDS was less than 1.71 standard deviation (SD) and decreased with the increase of BMISDS (β = -0.358, 95% CI: -0.474 to -0.241, p < 0.01) when BMISDS was greater than 1.71 SD.

CONCLUSIONS

The relationship between BMI and IGF-1 levels was found to depend on the type of variable, and extremely low or high BMI values could result in a tendency toward low IGF-1 levels, emphasizing the importance of maintaining a normal BMI range for normal IGF-1 levels.

Managing Estrogen Therapy in the Pituitary Patient

Growth hormone (GH) regulates metabolic and physical health in the adult human. Because the GH system is regulated by estrogens, therapeutic estrogen compounds are likely to affect metabolic health. Estrogens are available for oral and parenteral use in natural, prodrug, and synthetic formulations including selective estrogen receptor modulators (SERMs). This review covers the pharmacology of estrogen and the effects on GH action to inform judicious use in the pituitary patient. The effects on the GH system are route dependent due to first-pass hepatic metabolism. Oral but not parenteral estrogen compounds inhibit GH action, reducing hepatic insulin-like growth factor-1 (IGF-1) production, protein anabolism, and fat utilization. In patients with GH deficiency, oral estrogen therapy exacerbates the degree of hyposomatotrophism and attenuates the beneficial effects of GH replacement therapy, effects that are greater with contraceptive than replacement doses. Surveys report that less than one-fifth of hypopituitary women are appropriately replaced by a transdermal route and up to half on oral therapy are inappropriately treated with contraceptive steroids. In acromegaly, however, estrogens, especially synthetic formulations of greater potency, reduce IGF-1, improving disease control, an effect also observed in men treated with SERMs. The route-dependent effects and potency of estrogen formulations are important considerations for optimizing the management of hypogonadal patients with pituitary disease, in particular GH deficiency and acromegaly. For hypopituitary women, estrogens should be replaced by a nonoral route. For acromegaly, oral estrogen formulations can be considered as simple adjuvant therapy for disease control.

Estrogen signaling via estrogen receptor alpha and its implications for neurodegeneration associated with Alzheimer's disease in aging women

Estrogen receptor alpha (ERα) is a transcription factor activated by estrogenic hormones to regulate gene expression in certain organs, including the brain. In the brain, estrogen signaling pathways are central for maintaining cognitive functions. Herein, we review the neuroprotective effects of estrogens mediated by ERα. The estrogen/ERα pathways are affected by the reduction of estrogens in menopause, and this event may be a risk factor for neurodegeneration associated with Alzheimer's disease in women. Thus, developing a better understanding of estrogen/ERα signaling may be critical for defining new biomarkers and potential therapeutic targets for Alzheimer's disease in women.

Glucocorticoid induced bone disorders in children: Research progress in treatment mechanisms

Long-term or supra-physiological dose of glucocorticoid (GC) application in clinic can lead to impaired bone growth and osteoporosis. The side effects of GC on the skeletal system are particularly serious in growing children, potentially causing growth retardation or even osteoporotic fractures. Children's bone growth is dependent on endochondral ossification of growth plate chondrocytes, and excessive GC can hinder the development of growth plate and longitudinal bone growth. Despite the availability of drugs for treating osteoporosis, they have failed to effectively prevent or treat longitudinal bone growth and development disorders caused by GCs. As of now, there is no specific drug to mitigate these severe side effects. Traditional Chinese Medicine shows potential as an alternative to the current treatments by eliminating the side effects of GC. In summary, this article comprehensively reviews the research frontiers concerning growth and development disorders resulting from supra-physiological levels of GC and discusses the future research and treatment directions for optimizing steroid therapy. This article may also provide theoretical and experimental insight into the research and development of novel drugs to prevent GC-related side effects.

Considerations when treating male pubertal delay pharmacologically

INTRODUCTION

Delayed puberty, defined as the appearance of pubertal signs after the age of 14 years in males, usually affects psychosocial well-being. Patients and their parents show concern about genital development and stature. The condition is transient in most of the patients; nonetheless, the opportunity should not be missed to diagnose an underlying illness.

AREAS COVERED

The aetiologies of pubertal delay in males and their specific pharmacological therapies are discussed in this review.

EXPERT OPINION

High-quality evidence addressing the best pharmacological therapy approach for each aetiology of delayed puberty in males is scarce, and most of the current practice is based on small case series or unpublished experience. Male teenagers seeking attention for pubertal delay most probably benefit from medical treatment to avoid psychosocial distress. While watchful waiting is appropriate in 12- to 14-year-old boys when constitutional delay of growth and puberty (CGDP) is suspected, hormone replacement should not be delayed beyond the age of 14 years in order to avoid impairing height potential and peak bone mass. When primary or central hypogonadism is diagnosed, hormone replacement should be proposed by the age of 12 years provided that a functional central hypogonadism has been ruled out. Testosterone replacement regimens have been used for decades and are fairly standardised. Aromatase inhibitors have arisen as an interesting alternative for boy with CDGP and short stature. Gonadotrophin therapy seems more physiological in patients with central hypogonadism, but its relative efficacy and most adequate timing still need to be established.

Hormone supply to the pituitary gland: A comprehensive investigation of female‑related tumors (Review)

The hypothalamus acts on the pituitary gland after signal integration, thus regulating various physiological functions of the body. The pituitary gland includes the adenohypophysis and neurohypophysis, which differ in structure and function. The hypothalamus-hypophysis axis controls the secretion of adenohypophyseal hormones through the pituitary portal vein system. Thyroid-stimulating hormone, adrenocorticotropic hormone, gonadotropin, growth hormone (GH), and prolactin (PRL) are secreted by the adenohypophysis and regulate the functions of the body in physiological and pathological conditions. The aim of this review was to summarize the functions of female-associated hormones (GH, PRL, luteinizing hormone, and follicle-stimulating hormone) in tumors. Their pathophysiology was described and the mechanisms underlying female hormone-related diseases were investigated.

Efficacy and Safety of Letrozole in the Management of Constitutional Delay in Growth and Puberty: A Systematic Review and Meta-analysis

No meta-analysis is available which has analysed the role of letrozole in constitutional delay in growth and puberty (CDGP). Electronic databases were searched for randomized controlled trials (RCTs) involving children with CDGP receiving letrozole. Primary outcomes were changes in predicted adult height (PAH) and pubertal progression. Secondary outcomes were alterations in bone age (BA), hormonal markers of puberty, bone mineral density and side-effects. One hundred-thirty articles were reviewed, from which seven RCTs which fulfilled all criteria were analysed. Letrozole was superior to placebo [mean difference (MD) 4.63 cm (95% confidence interval (CI): 3.90-5.36); p<0.01; I²=0%] but not testosterone [MD: 2.21 cm (95% CI: -1.71-6.16); p=0.27; I²=98%] with regards to improvement in PAH after 12-months use. Letrozole was superior to both placebo [MD: 4.80 mL (95% CI: 0.57-9.03); p=0.03] and testosterone [MD: 3.36 mL (95% CI: 0.58-6.75); p=0.02; I²=0%] with regards to improvement in testicular volume after 12-months use. Letrozole tended to be superior to testosterone [MD: -0.84 years (95% CI: 2.83-8.18); p=0.06; I²=0%] with regards to slowing in BA progression after 12-months use. Serum luteinizing hormone, follicle stimulating hormone, testosterone and inhibin-B were significantly higher after 6-months letrozole use compared to active as well as passive controls. No increased occurrence of adverse events, including spinal deformities, were noted with letrozole. Letrozole is safe and effective for improving height and pubertal outcomes in CDGP, and is better than testosterone with regards to improvement in testicular volume and may be better at delaying bone-age progression.

Effects of Tetraselmis chuii Microalgae Supplementation on Anthropometric, Hormonal and Hematological Parameters in Healthy Young Men: A Double-Blind Study

The aim of this study was to evaluate the effects of Tetraselmis chuii (TC) microalgae supplementation for sixty days on hematological, anthropometric and hormonal parameters in healthy young men. Forty-six men divided into a placebo group (PG; n = 16; 20.77 ± 2.7 years; 72.14 ± 7.18 kg; 1.76 ± 0.07 m), a group supplemented with 25 mg/day of TC (SG 25; n = 15; 20.40 ± 1.40 years; 71.28 ± 8.26 kg; 1.76 ± 0.05 m) and another group supplemented with 200 mg/day of TC (SG 200; n = 15; 20.83 ± 2.45 years; 72.30 ± 11.13 kg; 1.77 ± 0.08 m) participated in this double-blind study. PG ingested 200 mg/day of lactose powder. Participants underwent 4 assessments (baseline, month 1, month 2 and desadaptation) separated in time by an interval of thirty days. At SG 25 and SG 200, significant increases in percent muscle mass, erythropoietin, insulin-like growth factor 1, free testosterone, leukocytes, neutrophils and lymphocytes were observed (p < 0.05). Decreases in the levels of percent fat mass, platelets, hematocrit and mean corpuscular hemoglobin also occurred in these groups (p < 0.05). TC supplementation induced favorable changes on anthropometric, hematological and hormonal levels. In view of the data, it seems that the most effective dose was 25 mg/day of TC.

ERK1/2‐RSK regulation of oestrogen homeostasis

The molecular mechanisms regulating oestrogen homeostasis have been primarily studied in the mammary gland, which is the focus of this review. In the non-pregnant adult, the mammary gland undergoes repeated cycles of proliferation and apoptosis in response to the fluctuating levels of oestrogen that occur during the reproductive stage. Oestrogen actions are mediated through the steroid hormone receptors, oestrogen receptor α and β and through a G-protein coupled receptor. In the mammary gland, ERα is of particular importance and thus will be highlighted. Mechanisms regulating oestrogen-induced responses through ERα are necessary to maintain homeostasis given that the signalling pathways that are activated in response to ERα-mediated transcription can also induce transformation. ERK1/2 and its downstream effector, p90 ribosomal S6 kinase (RSK), control homeostasis in the mammary gland by limiting oestrogen-mediated ERα responsiveness. ERK1/2 drives degradation coupled ERα-mediated transcription, whereas RSK2 acts as a negative regulator of ERK1/2 activity to limit oestrogen responsiveness. Moreover, RSK2 acts as a positive regulator of translation. Thus, RSK2 provides both positive and negative signals to maintain oestrogen responsiveness. In addition to transmitting signals through tyrosine kinase receptors, ERK1/2-RSK engages with hedgehog signalling to maintain oestrogen levels and with the HIPPO pathway to regulate ERα-mediated transcription. Additionally, ERK1/2-RSK controls the progenitor populations within the mammary gland to maintain the ERα-positive population. RSK2 is involved in increased breast cancer risk in individuals taking oral contraceptives and in parity-induced protection against breast cancer. RSK2 and ERα may also co-operate in diseases in tissues outside of the mammary gland.

Estrogenic hormones receptors in Alzheimer's disease

Estrogens are hormones that play a critical role during development and growth for the adequate functioning of the reproductive system of women, as well as for maintaining bones, metabolism, and cognition. During menopause, the levels of estrogens are decreased, altering their signaling mediated by their intracellular receptors such as estrogen receptor alpha and beta (ERα and ERβ), and G protein-coupled estrogen receptor (GPER). In the brain, the reduction of molecular pathways mediated by estrogenic receptors seems to favor the progression of Alzheimer's disease (AD) in postmenopausal women. In this review, we investigate the participation of estrogen receptors in AD in women during aging.

Impact of Estrogen Withdrawal and Replacement in Female Mice along the Intestinal Tract. Comparison of E2 Replacement with the Effect of a Mixture of Low Dose Pollutants

Postmenopausal women represent a vulnerable population towards endocrine disruptors due to hormonal deficit. We previously demonstrated that chronic exposure of ovariectomized C57Bl6/J mice fed a high-fat, high-sucrose diet to a low-dose mixture of chemicals with one dioxin, one polychlorobiphenyl, one phthalate, and bisphenol A triggered metabolic alterations in the liver but the intestine was not explored. Yet, the gastrointestinal tract is the main route by which pollutants enter the body. In the present study, we investigated the metabolic consequences of ovarian withdrawal and E2 replacement on the various gut segments along with investigating the impact of the mixture of pollutants. We showed that genes encoding estrogen receptors (Esr1, Gper1 not Esr2), xenobiotic processing genes (e.g., Cyp3a11, Cyp2b10), and genes related to gut homeostasis in the jejunum (e.g., Cd36, Got2, Mmp7) and to bile acid biosynthesis in the gut (e.g., Fgf15, Slc10a2) and liver (e.g., Abcb11, Slc10a1) were under estrogen regulation. Exposure to pollutants mimicked some of the effects of E2 replacement, particularly in the ileum (e.g., Esr1, Nr1c1) suggesting that the mixture had estrogen-mimetic activities. The present findings have important implications for the understanding of estrogen-dependent metabolic alterations with regards to situations of loss of estrogens as observed after menopause.