1 Copyright © 2005 Mosby, Inc. All rights reserved. Chapter 16 Endocrine System

2 Copyright © 2005 Mosby, Inc. All rights reserved. The Endocrine System

3 Copyright © 2005 Mosby, Inc. All rights reserved. Mechanisms of Hormone Action Endocrine glands secrete chemicals (hormones) into the blood Hormones perform general functions of communication and control, but a slower, longer-lasting type of control than that provided by nerve impulses Cells acted on by hormones are called target organ cells 3

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5 Regulation of Hormone Secretion Hormone secretion is controlled by homeostatic feedback Negative feedback—mechanisms that reverse the direction of a change in a physiological system Positive feedback—(uncommon) mechanisms that amplify physiological changes 5

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7 Mechanisms of Endocrine Disease Hypersecretion—secretion of excess hormone Hyposecretion—insufficient hormone secretion Polyendocrine disorders—hyper- or hyposecretion of more than one hormone Target cell insensitivity produces results similar to hyposecretion Endocrinologists have developed many different strategies for treatment (e.g., surgery and hormone therapy) 7

8 Copyright © 2005 Mosby, Inc. All rights reserved. Pituitary Gland Anterior pituitary gland Names of major hormones Thyroid-stimulating hormone (TSH) Adrenocorticotropic hormone (ACTH) Follicle-stimulating hormone (FSH) Luteinizing hormone (LH) Growth hormone (GH) Prolactin (lactogenic hormone) 8

9 Copyright © 2005 Mosby, Inc. All rights reserved. Pituitary Gland Functions of major hormones TSH—stimulates growth of the thyroid gland; also stimulates it to secrete thyroid hormone ACTH—stimulates growth of the adrenal cortex and stimulates it to secrete glucocorticoids (mainly cortisol) FSH—initiates growth of ovarian follicles each month in the ovary and stimulates one or more follicles to develop to the stage of maturity and ovulation; FSH also stimulates estrogen secretion by developing follicles; stimulates sperm production in the male 9

10 Copyright © 2005 Mosby, Inc. All rights reserved. Pituitary Gland Functions of major hormones LH—acts with FSH to stimulate estrogen secretion and follicle growth to maturity; causes ovulation; causes luteinization of the ruptured follicle and stimulates progesterone secretion by corpus luteum; causes interstitial cells in the testes to secrete testosterone in the male 10

11 Copyright © 2005 Mosby, Inc. All rights reserved. Pituitary Gland GH—stimulates growth by accelerating protein anabolism; also accelerates fat catabolism and slows glucose catabolism; by slowing glucose catabolism, tends to increase blood glucose to higher than normal level (hyperglycemia) Hypersecretion during childhood results in gigantism and during adulthood results in acromegaly Hyposecretion during childhood results in pituitary dwarfism Prolactin or lactogenic hormone—stimulates breast development during pregnancy and secretion of milk after the delivery of the baby 11

12 Copyright © 2005 Mosby, Inc. All rights reserved. Pituitary Gland Posterior pituitary gland Names of hormones Antidiuretic hormone (ADH) Hyposecretion causes diabetes insipidus, characterized by excessive volume of urine Oxytocin (OT) 12

13 Copyright © 2005 Mosby, Inc. All rights reserved. Pituitary Gland Functions of hormones ADH—accelerates water reabsorption from urine in the kidney tubules into the blood, thereby decreasing urine secretion Oxytocin—stimulates the pregnant uterus to contract; may initiate labor; causes glandular cells of the breast to release milk into ducts 13

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15 Copyright © 2005 Mosby, Inc. All rights reserved. Hypothalamus Actual production of ADH and oxytocin occurs in the hypothalamus After production in the hypothalamus, hormones pass along axons into the pituitary gland The secretion and release of posterior pituitary hormones is controlled by nervous stimulation The hypothalamus controls many body functions related to homeostasis (temperature, appetite, and thirst) 15

16 Copyright © 2005 Mosby, Inc. All rights reserved. Thyroid Gland Names of hormones Thyroid hormone—thyroxine (T 4 ) and triiodothyronine (T 3 ) Calcitonin (CT) Functions of hormones Thyroid hormones—accelerate catabolism (increase the body’s metabolic rate) Calcitonin—decreases the blood calcium concentration by inhibiting breakdown of bone, which would release calcium into the blood 16

17 Copyright © 2005 Mosby, Inc. All rights reserved. Thyroid Gland Hyperthyroidism (hypersecretion of thyroid hormones) increases metabolic rate Characterized by restlessness and exophthalmos (protruding eyes) 17

18 Copyright © 2005 Mosby, Inc. All rights reserved. Thyroid Gland Hypothyroidism (hyposecretion of thyroid hormones) May result from different conditions Simple goiter—painless enlargement of thyroid caused by dietary deficiency of iodine Hyposecretion during early development may result in cretinism (retardation) and during adulthood in myxedema (characterized by edema and sluggishness) 18

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20 Copyright © 2005 Mosby, Inc. All rights reserved. Parathyroid Glands Name of hormone—parathyroid hormone (PTH) Function of hormone—increases blood calcium concentration by increasing the breakdown of bone with the release of calcium into the blood 20

21 Copyright © 2005 Mosby, Inc. All rights reserved. Pancreatic Islets Names of hormones Glucagon—secreted by alpha cells Insulin—secreted by beta cells Functions of hormones Glucagon increases the blood glucose level by accelerating liver glycogenolysis (conversion of glycogen to glucose) 21

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23 Copyright © 2005 Mosby, Inc. All rights reserved. Pancreatic Islets Functions of hormones Insulin decreases the blood glucose by accelerating the movement of glucose out of the blood into cells, which increases glucose metabolism by cells 23

24 Copyright © 2005 Mosby, Inc. All rights reserved. Pancreatic Islets Diabetes mellitus Type 1 results from hyposecretion of insulin Type 2 results from target cell insensitivity to insulin Glucose cannot enter cells and thus blood glucose levels rise, producing glycosuria (glucose in the urine) 24

25 Copyright © 2005 Mosby, Inc. All rights reserved. Female Sex Glands The ovaries contain two structures that secrete hormones—the ovarian follicles and the corpus luteum Effects of estrogen (feminizing hormone) Development and maturation of breasts and external genitals Development of adult female body contours Initiation of menstrual cycle 25

26 Copyright © 2005 Mosby, Inc. All rights reserved. Male Sex Glands The interstitial cells of testes secrete the male hormone testosterone Effects of testosterone (masculinizing hormone) Maturation of external genitals Beard growth 26

27 Copyright © 2005 Mosby, Inc. All rights reserved. Male Sex Glands Effects of testosterone Voice changes at puberty Development of musculature and body contours typical of the male 27

28 Copyright © 2005 Mosby, Inc. All rights reserved. Thymus Name of hormone—thymosin Function of hormone—plays an important role in the development and function of the body’s immune system 28

29 Copyright © 2005 Mosby, Inc. All rights reserved. Other Endocrine Structures Many organs (e.g., the stomach, intestines, and kidney) produce endocrine hormones The atrial wall of the heart secretes atrial natriuretic hormone (ANH), which stimulates sodium loss from the kidneys Fat-storing cells secrete leptin, which controls how full or hungry we feel 29

30 Copyright © 2005 Mosby, Inc. All rights reserved. Endocrine Glands (cont’d) pituitary (cont’d) anterior lobe produces hormones (cont’d) antidiuretic hormone (ADH) oxytocin hypothalamus: located near the pituitary gland in the brain; which secretes “releasing” hormone that functions to stimulate or inhibit the release of pituitary gland hormones

31 Copyright © 2005 Mosby, Inc. All rights reserved. Endocrine Glands (cont’d) thyroid: largest endocrine gland located in the neck below the larynx produces hormones triiodothyronine (T 3 ) thyroxine (T 4 ) parathyroid: four small bodies lying directly behind the thyroid produces hormone parathormone (PTH)

32 Copyright © 2005 Mosby, Inc. All rights reserved. Endocrine Glands (cont’d) islets of Langerhans: clusters of endocrine tissue found throughout the pancreas produces hormones insulin glucagon

33 Copyright © 2005 Mosby, Inc. All rights reserved. Endocrine Glands (cont’d) adrenal glands: paired glands, one above each kidney. The outer portion is called the cortex, and the inner portion is called the medulla. produces hormones cortisol (hydrocortisone) Aldosterone epinephrine (adrenaline)

34 Copyright © 2005 Mosby, Inc. All rights reserved. Combining Forms for the Endocrine System aden/o adren/o, adrenal/o cortic/o endocrin/o parathyroid/o thyroid/o, thyr/o

35 Copyright © 2005 Mosby, Inc. All rights reserved. Combining Forms Commonly for the Endocrine System (cont’d) acr/o calc/i dips/o kal/i natr/o

36 Copyright © 2005 Mosby, Inc. All rights reserved. Suffix -drome

37 Copyright © 2005 Mosby, Inc. All rights reserved. Disease and Disorder Terms Built from Word Parts acromegaly adenomalacia adenomegaly adrenalitis adrenomegaly calcipenia hypercalcemia hyperglycemia hyperkalemia hypocalcemia

38 Copyright © 2005 Mosby, Inc. All rights reserved. Helpful Information hypocalcemia and calcipenia both mean a deficiency of calcium

39 Copyright © 2005 Mosby, Inc. All rights reserved. Disease and Disorder Terms Not Built from Word Parts acidosis Addison’s disease cretinism Cushing’s syndrome diabetes insipidus (DI) diabetes mellitus (DM) gigantism goiter Graves’ disease

40 Copyright © 2005 Mosby, Inc. All rights reserved. Cushing Syndrome

41 Copyright © 2005 Mosby, Inc. All rights reserved. Goiter

42 Copyright © 2005 Mosby, Inc. All rights reserved. Surgical Terms Built from Word Parts adenectomy adrenalectomy parathyroidectomy thyroidectomy thyroidotomy thyroparathyroidectomy

43 Copyright © 2005 Mosby, Inc. All rights reserved. Diagnostic Not Built from Word Parts Diagnostic imaging radioactive iodine uptake test (RAIU) thyroid scan Laboratory fasting blood sugar (FBS) thyroxine level (T 4 ) thyroid-stimulating hormone level (TSH)

44 Copyright © 2005 Mosby, Inc. All rights reserved. Complementary Terms Built from Word Parts adrenopathy calcipenia cortical endocrinologist endocrinology endocrinopathy polydipsia syndrome

45 Copyright © 2005 Mosby, Inc. All rights reserved. Complementary Terms Not Built from Word Parts exophthalmos hormone metabolism

46 Copyright © 2005 Mosby, Inc. All rights reserved. Abbreviations DI DM FBS RAIU T4