cortisol and stress

cortisol and stress - 1 Sujana Gottumukkala Bio 37 s07 The...

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Sujana Gottumukkala Bio 37 s07 The Role of Cortisol in LH Suppression as a Response to Psychological Stress INTRODUCTION: Cortisol is the main glucocorticoid steroid hormone in humans and is released by the adrenal cortex upon the activation of the hypothalamic-pituitary-adrenal (HPA) axis. When stimulated, the hypothalamus secretes corticotropin-releasing hormone (CRH), which then interacts with its G-protein coupled receptors in the corticotrophic cell and works synergistically with arginine-vasopressin (AVP) to activate the POMC gene [1]. In addition to its other functions, the POMC gene causes the anterior pituitary to synthesize and secrete ACTH, a fairly short chain peptide that causes the adrenal cortex to secrete glucocorticoids such as cortisol along with other steroid hormones. After the secretion of cortisol by the adrenal cortex, cortisol-binding globulin made by the liver binds to the glucocorticoid to prevent its premature degradation and transport it through the plasma to its target cell. Upon reaching its target cell, cortisol disassociates from the binding globulin and binds to the inactive cytoplasmic glucocorticoid receptor (GR) to cause activation of the GR. The GR then moves into the nucleus, where it homodimerizes and binds to the cortisol response element (CRE) to activate cellular responses. Cortisol also acts as a feedback mechanism for the entire pathway at the pituitary level and suppresses the further secretion of ACTH. Under normal circumstances, cortisol is important in maintaining normal blood pressure and cellular concentrations of enzymes crucial to metabolic homeostasis [2]. It is also useful in suppressing inflammatory immune responses and is glucocorticoids are often taken to treat a variety of conditions in which the immune system is overly active, such as simple allergies, asthma, and lupus. Cortisol is also considered to be extremely important for human development during the fetal and neonatal periods, and is believed to be necessary for the proper differentiation of human tissues [2]. However, in situations involving either physical or psychological stress, CRH secretion is increased, which overcomes the suppression of ACTH via cortisol feedback to increase cortisol secretion. As suppression of pulsatile luteinizing hormone (LH) has 1
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also been associated with stressful situations, increased glucocorticoid secretion has been suggested to inhibit the activity of the gonadal axis [1]. GnRH action upon the gonadotrope is necessary for LH secretion and LH action in the female reproductive system is in turn essential for the secretion of progesterone by the fecal cell. Furthermore, since fluctuations in progesterone concentration are key to the menstrual cycle, LH suppression would result in a severe disruption of menses. The amenorrhea experienced by many women during periods of stress [1] can thus be explained by the hypothesis that the increased glucocorticoid secretion that occurs in stressful situations suppresses LH secretion by the gonadotrope. In their study, Breen et al attempt to prove that glucocorticoids such as cortisol
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This note was uploaded on 05/01/2008 for the course BIOL 37 taught by Professor Witters during the Spring '07 term at Dartmouth.

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cortisol and stress - 1 Sujana Gottumukkala Bio 37 s07 The...

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