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Controlled Release of Hormones by Pellet Implants
Published in Emmanuel Opara, Controlled Drug Delivery Systems, 2020
Hormones are biological molecules secreted by the endocrine glands, circulate in the blood stream, and influence the target cell by using specific receptors. Almost every cell of our body is a target for one or more than one hormone. Hormones function as chemical messengers used by endocrine system to communicate and coordinate between various organ systems in the body. Hormones govern various physiological, morphological, and behavioral phenomena. The pleiotropic potential of hormones –that is their capacity to regulate multiple traits simultaneously – renders them particularly suited to control complex physiological and phenotype changes (Hau 2007). Studying the effect of a given hormone system in an experimental setup has been there for centuries. In one of the first endocrine experiments ever recorded, Professor Arnold A. Berthold (1803–1861) of Gottingen did a series of tests on roosters in 1849 while he was curator of the local zoo. Berthold found that a rooster’s comb is an androgen-dependent structure. Following castration, the comb atrophies, aggressive male behavior disappears, and interest in the hens is lost. Importantly, Berthold also found that these castration-induced changes could be reversed by administration of a crude testicular extract (or prevented by transplantation of the testes). Similarly, in 1889 Brown-Séquard reported the effect of testicular extract from animals in humans (Brown 1889).
Endocrine system
Published in David A Lisle, Imaging for Students, 2012
Endocrine syndromes associated with pathology of the pituitary gland and hypothalamus include:Pituitary dwarfismHypoplasia of adenohypophysisEctopic neurohypophysisAbsent pituitary stalkCentral diabetes insipidusDysfunction of neurohypophysis or hypothalamus due to tumour, Langerhans cell histiocytosis, infection or traumaPrecocious pubertyHamartoma or other neoplasm of hypothalamusHypersecretion syndromesPituitary adenomas (see Table 12.1).
Scope of the Problem
Published in Jason W. Birkett, John N. Lester, Endocrine Disrupters in Wastewater and Sludge Treatment Processes, 2002
The endocrine system consists of several glands in different areas of the body that produce hormones with different functions.69 Endocrine glands are ductless and consist of the hypothalamus, pituitary, thyroid, parathyroid, adrenal glands, the pineal body, and the gonads. These synthesize hormones, which are then transported via the bloodstream to the target organs where they are used to invoke a natural response. These target cells are comprised of a binding site (receptor) and an effector site.70 When hormones attach to the receptor, the effector site is altered, which, in turn, produces the desired response (Figure 1.1a). Some “free” hormone molecules will never reach the receptors and are inactivated prior to excretion, primarily by the liver and kidneys in a process called metabolic clearance. This process varies with the type of hormones, but the effective “life span” of a hormone in the body is from a few minutes to several hours. Thus, if the metabolic clearance rate is low, the hormone stays in the body longer and thus its availability to interact with receptors increases, resulting in more responses.
Urinary levels of phthalate esters and heavy metals in adolescents with thyroid colloid cysts
Published in International Journal of Environmental Health Research, 2022
S. Songül Yalçin, İzzet Erdal, Semra Çetinkaya, Berna Oğuz
Phthalates are added to food packages, drugs, toys, cosmetics, detergents and pesticides for technological and industrial purposes (Wang et al. 2019). Heavy metals are found in nature and can be consumed through different routes with dietary supplements or cigarettes, and contaminated air, water and food in daily life (Tchounwou et al. 2012). WHO has announced four heavy metals including As, Cd, Pb and Hg in ‘ten chemicals of major public health concern’ (WHO, 2010). Their uncontrolled usage poses serious threat to the environment and increases the possibility of adverse effects on human health. In addition, children are more sensitive to the toxicity of contaminants than adults and exposures in children are reported to be higher than adults (Wang et al. 2019; Zhou and Ma 2019). Phthalates and heavy metals are shown to interfere with hormonal processes, including endocrine disruptions in both children and adults (Boas et al. 2006; Meeker and Ferguson 2011; de Cock et al. 2014). Some endocrine disrupting chemicals (EDCs) may change thyrotropin-releasing hormone (TRH)-stimulated thyroid-stimulating hormone (TSH) secretion or inhibit iodide uptake and thyroid peroxidase (TPO). Moreover, the proposed indirect effects include changing thyroxine-binding globulin (TBG) and albumin levels, the T4:T3 ratio, the levels of deiodinase enzyme, and the clearance of thyroid hormones with glucuronyltransferase (UDP-GT) (Price et al. 1988; Sutcliffe and Harvey 2015). The suggested direct and indirect effects of EDCs on thyroid hormone homeostasis require additional studies on the thyroid gland.
Urinary Isoflavones Levels in Relation to Serum Thyroid Hormone Concentrations in Female and Male Adults in the U.S. General Population
Published in International Journal of Environmental Health Research, 2021
Patricia A. Janulewicz, Jeffrey M. Carlson, Amelia K. Wesselink, Lauren A. Wise, Elizabeth E. Hatch, Lariah M. Edwards, Junenette L. Peters
Thyroid hormones (TH) are controlled through the hypothalamic-pituitary-thyroid (HPT) axis and are crucial for the regulation of many biological systems. The HPT axis is complex and sensitive to perturbations. The hypothalamus, located in the central nervous system, produces thyrotropin-releasing hormone (TRH), and sends it to the pituitary gland, which releases thyroid stimulating hormone (TSH). TSH binds to receptors on the thyroid gland and stimulates the synthesis and release of thyroid hormones, thyroxine (T4) and triiodothyronine (T3), into peripheral circulation. Proper production of these hormones is largely dependent on iodine levels (Rousset et al. 2000). Circulating TH levels are maintained by a feedback mechanism between the hypothalamus, pituitary gland, and thyroid gland (Rousset et al. 2000; Pearce and Braverman 2009; Gilbert et al. 2012). Optimal circulating TH levels are essential for normal fetal and child growth (Meeker 2012; DiVall 2013) and brain development (Meeker 2012), reproductive function, and metabolism (Meeker and Ferguson 2014).
Light exposure during late night attenuates the risk of scopolamine-induced Alzheimer disease in aged rats
Published in Egyptian Journal of Basic and Applied Sciences, 2020
Mona Abdel-Rahman, Seham Abdel-Kader, Heba El-Masry, Rehab E. El-Hennamy
Light, the most potent time cue of the SCN affects the circadian system differently according to the internal time of exposure. Light exposure during the biological evening, resulted in phase delays in the circadian system. Alternatively, light exposure during the biological morning (late hours of the subjected night) results in a phase advance [50]. Similarly, the circadian rhythm of melatonin, serotonin, ACh and norepinephrine showed a phase advance after light pulse exposure during late night. Moreover, the 5-HT contents elevated highly that associated with reduced levels of melatonin. Light at night causes a drop in norepinephrine stimulation of the pineal gland. Consequently, the activity of serotonin N- acetyltransferase is decreased [51]. Taken together, it is obvious that the light pulse affected the neurotransmitter levels positively and shifted their phase, hence it could improve neural and circadian abnormalities associated with the aging process.