Chapter 5

Medicinal Chemistry and the Endocrine System

Robert E. Smith


The endocrine system consists of cells, glands and tissues that secrete hormones into the bloodstream that affect physiological and behavioral function and activities [1]. This is in contrast to the exocrine system that secretes substances into ducts. The hypothalamus connects the nervous and endocrine systems to each other through the pituitary gland, or hypophysis. It helps control body temperature, hunger, parenting and attachment behavior, thirst, fatigue, sleep, circadian rhythms and other activities of the autonomic nervous system. Darkness causes the pineal gland to secrete N-acetyl-5-methoxytryptamine, which is better known as melatonin. Melatonin is part of the system that regulates the sleep-wake cycle. It causes drowsiness and lowers the body temperature. The anterior lobe of the pituitary gland secretes growth hormone (GH), beta-endorphin, luteinizing hormone (LH), follicle stimulating hormone (FSH), melanocyte stimulating hormone (MSH), adrenocorticotropic hormone (ACTH), thyroid stimulating hormone (TSH) and prolactin (PRL). The posterior lobe stores vasopressin, also known as antidiuretic hormone (ADH) and oxytocin (OXT). The thyroid gland helps control how fast a body uses energy and makes proteins as well as influencing the sensitivity of the body to other hormones. It does this by producing T3 and T4, which are made from tyrosine and iodine. The stomach, duodenum, liver, pancreas and kidneys all secrete hormones. The kidneys secrete renin, erythropoietin, calcitrol and thrombopoietin. They regulate pH, electrolytes and blood pressure. The adrenal glands produce hormones in response to stress by synthesizing corticosteroids such as cortisol and catecholamines, such as adrenaline (epinephrine) and noradrenaline (norepinephrine). They also produce androgens in their innermost cortical layer. The adrenal glands affect kidney function by secreting aldosterone. The testes, ovarian follicle and corpus luteum are in the endocrine system, as are the placenta and uterus when a woman is pregnant. The testes secrete androgens (mostly testosterone), estradiol and inhibin. They stimulate or control the development and maintenance of male characteristics by binding to androgen receptors. This includes the activity of the male sex organs and development of male secondary sex characteristics. Androgens are also the original anabolic steroids and the precursor of all estrogens. The endocrine system also regulates the concentration of Ca2+. The parathyroid gland secretes the parathyroid hormone (PTH), which stimulates Ca2+ release from bones, stimulates osteoclasts and Ca2+ reabsorption in the kidneys. Calcium regulation also occurs in the skin, which secretes the prehormone calcidiol (25-hydroxyvitamin D3), the inactive form of vitamin D. The major endocrine systems are the TRH-TSH-Y3/T4, the GnRH LH/FSH-sex hormones, the CRH-ACTH-cortisol, the renin-angiotensin-aldosterone system and the leptin vs insulin system. The TRH-TSH-Y3/T4 system is also called [1].

Total Pages: 198-233 (36)

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