Explore chapters and articles related to this topic
Tests on Naturally Voided Body Fluids
Published in Robert B. Northrop, Non-Invasive Instrumentation and Measurement in Medical Diagnosis, 2017
Tests to determine the concentrations of certain hormones in the urine can also aid in the diagnosis of hormonal regulatory disorders. In Table 8.9derived from data in Collins (1968), we illustrate the diseases and conditions associated with unbalances of urine 17-hydroxycorticosteroids, 17-ketosteroids, aldosterone, and gonadotropins. At least 13 steroid hormones are made in the adrenal cortex; it is a busy place. The 17-hydroxycorticosteroids are produced from cholesterol in response to ACTH secreted by the anterior pituitary gland; they include the glucocorticoids hormones progesterone and cortisol. The 17-ketosteroids include the androgenic hormones dehydroepiandosterone (DEA), and testosterone (made in the testicles). The mineral corticoid, aldosterone, is also synthesized in the adrenal cortex (West 1985). Its principle role is in the regulation of plasma potassium ions (Northrop 2000). Human anterior pituitary gonadotropin hormones include the glycoproteins, follicle-stimulating hormone, and luteinizing hormone.
Human physiology, hazards and health risks
Published in Stephen Battersby, Clay's Handbook of Environmental Health, 2016
David J. Baker, Naima Bradley, Alec Dobney, Virginia Murray, Jill R. Meara, John O’Hagan, Neil P. McColl, Caryn L. Cox
The anterior pituitary releases the following:growth hormone;thyrotrophic hormone;adrenocorticotrophic hormone; andgonadotrophic hormones.
Reproduction, development and work
Published in Chris Winder, Neill Stacey, Occupational Toxicology, 2004
The process of maturation of the ova takes approximately 14 days. At the end of this time only one mature follicle, now an outswelling of the ovary, bursts and discharges its contents (including the ovum) into the abdominal cavity. This is known as ovulation. Ovulation is also stimulated by another trophic hormone secreted by the anterior pituitary, known as luteinising hormone (LH).
Influence of sex hormones status and type of training on regional bone mineral density in exercising females
Published in European Journal of Sport Science, 2023
Isabel Guisado-Cuadrado, Víctor M. Alfaro-Magallanes, Nuria Romero-Parra, Beatriz Rael, Amelia Guadalupe-Grau, Ana B. Peinado
Sex hormone fluctuations that occur across woman's lifespan may involve a decrease in serum oestradiol levels, such as menopause (Takahashi & Johnson, 2015), and the use of hormonal contraceptives (Martin et al., 2021). When menopause occurs, ovarian follicles are depleted and the ovary is unable to respond to even high levels of FSH and, consequently, oestradiol levels decrease (Takahashi & Johnson, 2015). On the other hand, oral contraceptive (OC) use causes an inhibition of the anterior pituitary, especially during the phase when hormonal contraceptives provide synthetic exogenous sex hormone doses, reducing the endogenous 17-β-oestradiol level (Willis et al., 2006). These lower oestradiol levels may lead to an imbalance between bone resorption and bone formation (Khosla et al., 2012), as well as affect the mechanosensitivity of osteocytes by reducing the stress response of bone cells (Klein-Nulend et al., 2015). In fact, several studies have shown lower BMD in postmenopausal females compared to premenopausal ones (Fan et al., 2022; Fu et al., 2011). Although theoretically this reduction in oestradiol may promote a loss of BMD, in the literature there is controversy about the effect of OC use on BMD (Rocca et al., 2021). This inconsistency in the results may come from the multiple factors that influence the effect of these OCs, such as the duration of the treatment (Jackowski et al., 2016; Wei et al., 2011), the dose of synthetic oestrogens or the age of initiation of the treatment (Biason et al., 2015).
Effects of whole-body vibration on reproductive physiology in a rat model of whole-body vibration
Published in Journal of Toxicology and Environmental Health, Part A, 2022
K. Krajnak, S. Waugh, D. Welcome, X.S. Xu, C. Warren, W. McKinney, R.G. Dong
qRT-PCR was performed to determine if exposure to WBV resulted in changes in transcript levels in the pituitary, ovaries, uteri, testes, and prostates of exposed animals using methods described in (Krajnak et al. 2010, 2009, 2007). RNA was isolated from each tissue using RNAeasy lipid Miniprep kits (cat # 74804; Qiagen, Valencia, CA), and first-strand cDNA was synthesized from 1 μg of total RNA using a Reverse Transcription System (Invitrogen; Carlsbad, CA). Melt curves were run for each transcript using each tissue. Samples that did not show a single defined melt peak in the 80°C range were not included in the dataset. To determine if the treatment resulted in a change in transcript levels, fold changes from the same-day controls were calculated. This was conducted by calculating the mean response for the control group and then subtracting the individual cycle time (CT) values for each sample from the average of the controls. Transcript levels for anti-oxidant enzymes, cytokines, factors involved in regulating cell cycle, and steroid hormone and anterior pituitary hormone receptors were measured in each tissue.
Zearalenone perturbs the circadian clock and inhibits testosterone synthesis in mouse Leydig cells
Published in Journal of Toxicology and Environmental Health, Part A, 2021
Lijia Zhao, Yaoyao Xiao, Cuimei Li, Jing Zhang, Yaojia Zhang, Meina Wu, Tiantian Ma, Luda Yang, Xiaoyu Wang, Haizhen Jiang, Qian Li, Hongcong Zhao, Yiqun Wang, Aihua Wang, Yaping Jin, Huatao Chen
Leydig cells are the primary producers of androgens. StAR, Cyp11a1, Cyp17a1, Hsd3b2, and Hsd17b3 are steroidogenic genes expressed in LCs that encode enzymes critical for androgen synthesis. The hypothalamic-pituitary axis plays an important role in regulating testosterone production. LH is produced by gonadotropic cells in the anterior pituitary gland. The released LH binds to its receptor on LCs and facilitates production of cAMP. Increases in cAMP levels stimulate translocation of cholesterol to the outer mitochondrial membrane. After transfer to the inner mitochondrial membrane through the action of StAR, this cholesterol is converted to pregnenolone by CYP11A1. Pregnenolone is finally metabolized to testosterone by the combined actions of HSD3B, CYP17A1, and HSD17B in the smooth endoplasmic reticulum (Tremblay 2015). Previous investigators demonstrated that plasma testosterone concentrations exhibit diurnal fluctuations in healthy young men, rats, and mice (Faiman and Winter 1971; Kinson and Liu 1973; Sayegh et al. 1990). It is of interest that Alvarez et al. (2008) noted that the expression levels of testosterone synthesis-related genes and proteins are decreased in testes of Bmal1-/- mice resulting in low serum testosterone levels. Zheng et al. (2019) reported that ZEA impaired synthesis and secretion of testosterone, consequently affecting the reproductive capability of male mammals. However, it is not known whether ZEA-mediated effects on testosterone production are associated with impairment of the circadian clock in mammalian LCs.