Atherosclerosis
George Feuer, Felix A. de la Iglesia in Molecular Biochemistry of Human Disease, 2020
The elimination of cholesterol metabolites takes place entirely through the stool, either as unchanged cholesterol, or bile acids produced in the liver, or coprostanol formed from cholesterol by bacterial action (Figure 13). Small amounts of cholesterol are converted to steroid hormones. The excreted cholesterol mixes with dietary cholesterol and probably limited amounts reenter the pool. Bile acids are reabsorbed efficiently via the enterohepatic circulation into the liver, and only small quantities leave the body (Figure 14). A fraction of cholesterol is excreted through the skin and in the milk during lactation. In the production of bile acids, the conversion of cholesterol to 7α-hydroxycholesterol is the rate-limiting step. The enzyme is located in the microsomal fraction of the hepatocyte and has a short halflife of 2.5 to 3.0 h. Bile salts returning to the liver via the portal circulation exercise a feedback control on 7α-hydroxylase.521,576
Dictionary
Mario P. Iturralde in Dictionary and Handbook of Nuclear Medicine and Clinical Imaging, 1990
Hormone. Substance secreted by the endocrine, or ductless, glands that influences the activity of the various organs of the body and thus regulates the metabolic processes. Chemically, this represents a diverse group of compounds and can be divided into three classes: Polypeptide or protein hormones — those secreted by pituitary, parathyroid, and pancreas (for example, thyrotropin, TSH, growth hormone, HGH, follicle-stimulating hormone, FSH, parathormone, calcitonin, and insulin).Steroid hormone — those produced by the adrenal cortex and gonads (for example, aldosterone, corticosterone, testosterone, progesterone, and estrogens).Simple hormones — those produced by adrenal medulla and thyroid. These are neither protein nor steroid, but simple amino acid derivatives (for example, epinephrine, triiodothyronine [T3], and thyroxine [T4].
Bioscience indications for chronic disease management and neuromedical interventions following traumatic brain injury
Mark J. Ashley, David A. Hovda in Traumatic Brain Injury, 2017
The brain and nervous system produce steroids, referred to as neurosteroids, de novo and join the gonads, adrenals, and placenta as steroidogenic.224–227 Neurons and glia are involved in neurosteroid production, and production varies with location within the brain and distance from cell bodies.228 Mediation of neurosteroids is accomplished by direct or indirect modulation of neurotransmitter receptors or through ion-gated neurotransmitter receptors. Neurosteroid stimulation of neurotransmitter receptors is manifested by behavioral change, e.g., stimulation of GABAA receptors, resulting in decreases in anxiety, sedation, and seizure activity.229–239 Neurosteroids are considered to be broad-spectrum anticonvulsants and impact depression, learning, and memory; premenstrual syndrome; and alcohol withdrawal and, consequently, may merit consideration as an endocrine contribution to clinical manifestation of ABI.240 Hormone steroids act as chemical messengers and are synthesized from cholesterol. The major classes of steroid hormones include progestogens, androgens, estrogens, and corticosteroids.
Oxytocin modulates steroidogenesis-associated genes and estradiol levels in the placenta
Published in Systems Biology in Reproductive Medicine, 2023
Sung-Min An, Min Jae Kim, Jea Sic Jeong, So Young Kim, Da Som Kim, Beum-Soo An, Seung Chul Kim
Steroid hormones are primarily produced by a biological process called steroidogenesis, which is the process by which cholesterol is converted into several other steroid hormones. Humans and various mammals use cholesterol to synthesize steroid hormones in the reproductive glands and placenta (Payne and Hales 2004). During pregnancy, multiple steroid hormones released by the placenta perform a variety of roles, including placental trophoblast differentiation, expansion and maturation of the placental vessels, and uterine endovascular invasion by the placental trophoblast (extravillous cytotrophoblast) (Pepe and Albrecht 2008). One study demonstrated that CTB isolated form human placentas are capable of differentiating and fusing spontaneously to form functional STB as well as producing steroid hormones (Kliman et al. 1986). In addition, various studies have conducted research on synthesis of steroid hormones using JEG-3 cells (Samson et al. 2009; Cao et al. 2017; Karahoda et al. 2021). Since the process of synthesizing steroid hormones in the placenta has a large impact on the mother and fetus during pregnancy, in-depth studies on placental steroidogenesis are inevitable.
Human ovarian granulosa cells use clathrin-mediated endocytosis for LDL uptake: immunocytochemical and electron microscopic study
Published in Ultrastructural Pathology, 2023
Aynur Abdulova, Merjem Purelku, Hakan Sahin, Gamze Tanrıverdi
Steroidogenesis is a complex process between multiple enzymes and substrates by which cholesterol is converted into steroid hormones. Cholesterol is stored in lipid droplets (LDs) as cholesterol esters (CEs) within the steroidogenic tissue. The cholesterol that is required for steroidogenesis which is being initiated in response to a hormonal stimulus is provided by the mobilization of these stored CEs within the cells.3 There are two different forms of cholesterol which are known as high-density lipoprotein (HDL) and low-density lipoprotein (LDL). Studies are focused on the fact that granulosa cells use the LDL-receptor (LDLR)-mediated endocytic pathway for steroid biosynthesis. LDLR is an important protein that functions to mediate the uptake of LDL cholesterol, which is a specific substrate for steroid hormone production.3–5 Many different endocytic pathways have been described in eukaryotic cells, but the main pathway for LDL transport has been reported to be the clathrin-mediated endocytosis pathway.6,7 However, no study that clarifies LDL internalization in human granulosa cells and whether the clathrin-mediated endocytic pathway is functional in this process has yet been published.
The association of sex steroid hormone concentrations with hearing loss: a cross-sectional study
Published in Acta Oto-Laryngologica, 2023
Huifen Yang, Jing Li, Xinyuan Sun, Wangwei Li, Yuan Wang, Caiqin Huang
Sex steroid hormones include estrogens and androgens, whose concentrations and functions are different in men and women. Traditionally, estrogens and androgens were considered to be female and male hormones, respectively. They were also shown to be multitasking hormones that played prominent roles in libido and reproduction and contributed to physiological and growth mechanisms [3,4]. It has been reported that estradiol protected against noise-induced hearing loss in female mice [5]. Polycystic ovary syndrome patients with increased testosterone levels had a higher rate of hearing loss [6]. Those studies indicated that sex steroid hormone levels may be vital to hearing. Therefore, we extracted hearing condition data from the National Health and Nutrition Examination Survey (NHANES). This study aimed to explore the associations between sex steroid hormones and speech-frequency hearing loss.
Related Knowledge Centers
- Adrenal Cortex
- Glucocorticoid
- Gonad
- Mineralocorticoid
- Placenta
- Steroid
- Receptor
- Corticosteroid
- Hormone
- Sex Hormone