THIRD EDITION HUMAN PHYSIOLOGY AN INTEGRATED APPROACH Dee

THIRD EDITION HUMAN PHYSIOLOGY AN INTEGRATED APPROACH Dee Unglaub Silverthorn, Ph. D. Chapter 7 The Endocrine System Power. Point® Lecture Slide Presentation by Dr. Howard D. Booth, Professor of Biology, Eastern Michigan University Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

About this Chapter • Expand on integration of chemical and nervous coordination • Form and function of key endocrine glands • Classification, structure and synthesis of hormones • Pathways of nervous to endocrine regulation • How target cells/tissues are impacted • Some pathologies of the endocrine system Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Summary of the Endocrine System Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 7 -2 -1: ANATOMY SUMMARY: Hormones

Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Summary of the Endocrine System Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 7 -2 -2: ANATOMY SUMMARY: Hormones

Summary of the Endocrine System Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 7 -2 -3: ANATOMY SUMMARY: Hormones

Mechanism of Hormone Action • Hormones produce one or more of the following cellular changes in target cells • Alter plasma membrane permeability • Stimulate protein synthesis • Activate or deactivate enzyme systems • Induce secretory activity • Stimulate mitosis Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Chemical Regulating Systems: Overview • Pheromones: organism to organism communication • Hormones: cell to cell communication molecules • Made in gland(s) or cells • Transported by blood • Distant target tissue receptors • Activates physiological response Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Protein and Polypeptide Hormones: Synthesis and Release Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 7 -3: Peptide hormone synthesis, packaging, and release

Hormones • Three types • Proteins • Glycoproteins • Small peptides • Large proteins • Lipids • Cholesterol derivatives • Eicosanoids • Amino acid derivatives (Amine Hormones) Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Protein and Polypeptide Hormone Receptors • Surface receptor • Hormone binds • Transduction • Enzyme activation • Open channels • Second messenger systems • Synthesis Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 7 -5: Membrane receptors for peptide hormones

Amine Hormone Structures and Functions • Made of 1 -2 amino acids, derived from tyrosine or tryptophan • Receptors • Surface • Intracellular • Small size, OH group • Benzine ring • Examples • Thyroxin • Epinephrine Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Amine Hormone Structures and Functions Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 7 -8: Tyrosine-derived amine hormones

Steroid Hormones: Structure and Action • From cholesterol, lipophilic, enter target cell, • Cytoplasmic or nuclear receptors (mostly) • Activate DNA for protein synthesis • Slower acting, longer half-life • Examples: cortisol, estrogen & testosterone Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Steroid Hormones • Steroid hormones and thyroid hormone diffuse easily into their target cells • Once inside, they bind activate a specific intracellular receptor • The hormone-receptor complex travels to the nucleus and binds a DNA-associated receptor protein • This interaction prompts DNA transcription to produce m. RNA • The m. RNA is translated into proteins, which bring about a cellular effect Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Steroid Hormones: Structure and Action Figure 7 -7: Steroid hormone action Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Steroid Hormones: Structure and Action Figure 7 -6: Steroid hormones are derived from cholesterol Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Target Cell Specificity • Hormones circulate to all tissues but only activate cells referred to as target cells • Target cells must have specific receptors to which the hormone binds • These receptors may be intracellular or located on the plasma membrane Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Target Cell Activation • Target cell activation depends on three factors • Blood levels of the hormone • Relative number of receptors on the target cell • The affinity of those receptors for the hormone • Up-regulation – target cells form more receptors in response to the hormone • Down-regulation – target cells lose receptors in response to the hormone Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Hormone Concentrations in the Blood • Hormones circulate in the blood in two forms – free or bound • Steroids and thyroid hormone are attached to plasma proteins • All others are unencumbered Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Hormone Concentrations in the Blood • Concentrations of circulating hormone reflect: • Rate of release • Speed of inactivation and removal from the body • Hormones are removed from the blood by: • Degrading enzymes • The kidneys • Liver enzyme systems Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Control of Hormone Release • Blood levels of hormones: • Are controlled by negative feedback systems • Vary only within a narrow desirable range • Hormones are synthesized and released in response to humoral, neural, and hormonal stimuli Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Endocrine Reflex Pathways: Overview • Stimulus • Afferent signal • Integration • Efferent signal (the hormone) • Physiological action • Negative feedback Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Multiple Stimuli for Hormone Release: Nervous & Endocrine • Stimuli • Stretch • Glucose • Insulin levels • Reflex • Lower blood glucose • Reduces stimulus • Reduces insulin release Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Endocrine Reflex Pathways: Overview Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 7 -9: Hormones may have multiple stimuli for their release

Neurohormones: secreted into the Blood by Neurons • Adrenal Medulla–catecholamines • Hypothalamus to: • Anterior pituitary • Trophic Hs • Growth H. • Prolactin • Posterior pituitary • Vasopressin • Oxytocin Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Neurohormones: secreted into the Blood by Neurons Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 7 -12: Synthesis, storage, and release of posterior pituitary hormones

Pituitary-Hypothalamic Relationships: Posterior Lobe • The posterior lobe is a downgrowth of hypothalamic neural tissue • Has a neural connection with the hypothalamus (hypothalamic-hypophyseal tract) • Nuclei of the hypothalamus synthesize oxytocin and antidiuretic hormone (ADH) • These hormones are transported to the posterior pituitary Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

The Posterior Pituitary and Hypothalamic Hormones • Posterior pituitary – made of axons of hypothalamic neurons, stores antidiuretic hormone (ADH) and oxytocin • ADH and oxytocin are synthesized in the hypothalamus • ADH influences water balance • Oxytocin stimulates smooth muscle contraction in breasts and uterus • Both use PIP-calcium second-messenger mechanism Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Oxytocin • Oxytocin is a strong stimulant of uterine contraction • Regulated by a positive feedback mechanism to oxytocin in the blood • This leads to increased intensity of uterine contractions, ending in birth • Oxytocin triggers milk ejection (“letdown” reflex) in women producing milk Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Oxytocin • Synthetic and natural oxytocic drugs are used to induce or hasten labor • Plays a role in sexual arousal and satisfaction in males and nonlactating females Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Antidiuretic Hormone (ADH) • ADH helps to avoid dehydration or water overload • Prevents urine formation • Osmoreceptors monitor the solute concentration of the blood • With high solutes, ADH is synthesized and released, thus preserving water • With low solutes, ADH is not released, thus causing water loss from the body • Alcohol inhibits ADH release and causes copious urine output Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Pituitary-Hypothalamic Relationships: Anterior Lobe • The anterior lobe of the pituitary is an outpocketing of the oral mucosa • There is no direct neural contact with the hypothalamus Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Endocrine Control: Three Levels of Integration Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 7 -13: Hormones of the hypothalamic-anterior pituitary pathway

Adenohypophyseal Hormones • The six hormones of the adenohypophysis: • Are abbreviated as GH, TSH, ACTH, FSH, LH, and PRL • Regulate the activity of other endocrine glands • In addition, pro-opiomelanocortin (POMC): • Has been isolated from the pituitary • Is enzymatically split into ACTH, beta endorphin, and several Melanocyte Stimulating Hormones and Lipotropins Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Diagram of the POMC Gene • Pro-opiomelanocortin (POMC) is a precursor polypeptide with 241 amino acid residues. POMC is synthesized from the 285 -amino-acid-long polypeptide precursor pre-pro-opiomelanocortin (pre-POMC), by the removal of a 44 -amino-acid-long signal peptide sequence during translation. Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Activity of the Adenohypophysis • The hypothalamus sends a chemical stimulus to the anterior pituitary • Releasing hormones stimulate the synthesis and release of hormones • Inhibiting hormones shut off the synthesis and release of hormones Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Activity of the Anterior Pituitary (Adenophypophysis) • The tropic hormones that are released are: • Thyroid-stimulating hormone (TSH), Thyrotropin • Adrenocorticotropic hormone (ACTH), Corticotropin • Follicle-stimulating hormone (FSH), a Gonadotropin • Luteinizing hormone (LH), a Gonadotropin • Growth Hormone (GH), Somatotropin Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Endocrine Control: Three Levels of Integration • Hypothalamic stimulation–from CNS • Pituitary stimulation–from hypothalamic trophic Hs • Endocrine gland stimulation–from pituitary trophic Hs Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Negative Feedback Controls: Long & Short Loop Reflexes Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 7 -14: Negative feedback loops in the hypothalamicanterior pituitary pathway

Negative Feedback Controls: Long & Short Loop Reflexes Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 7 -15: Control pathway for cortisol secretion

Thyroid Gland • The largest endocrine gland, located in the anterior neck, consists of two lateral lobes connected by a median tissue mass called the isthmus • Composed of follicles that produce the glycoprotein thyroglobulin • Colloid (thyroglobulin + iodine) fills the lumen of the follicles and is the precursor of thyroid hormone • Other endocrine cells, the parafollicular cells, produce the hormone calcitonin Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Thyroid Gland Figure 16. 7 Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Thyroid Hormone • Thyroid hormone – the body’s major metabolic hormone • Consists of two closely related iodine-containing compounds • T 4 – thyroxine; has two tyrosine molecules plus four bound iodine atoms • T 3 – triiodothyronine; has two tyrosines with three bound iodine atoms Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Effects of Thyroid Hormone • TH is concerned with: • Glucose oxidation • Increasing metabolic rate • Heat production • TH plays a role in: • Maintaining blood pressure • Regulating tissue growth • Developing skeletal and nervous systems • Maturation and reproductive capabilities Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Synthesis of Thyroid Hormone • Thyroglobulin is synthesized and discharged into the lumen • Iodides (I–) are actively taken into the cell, oxidized to iodine (I 2), and released into the lumen • Iodine attaches to tyrosine, mediated by peroxidase enzymes, forming T 1 (monoiodotyrosine, or MIT), and T 2 (diiodotyrosine, or DIT) • Iodinated tyrosines link together to form T 3 and T 4 • Colloid is then endocytosed and combined with a lysosome, where T 3 and T 4 are cleaved and diffuse into the bloodstream Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Synthesis of Thyroid Hormone Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 16. 8

Transport and Regulation of TH • T 4 and T 3 bind to thyroxine-binding globulins (TBGs) produced by the liver • Both bind to target receptors, but T 3 is ten times more active than T 4 • Peripheral tissues convert T 4 to T 3 • Mechanisms of activity are similar to steroids • Regulation is by negative feedback • Hypothalamic thyrotropin-releasing hormone (TRH) can overcome the negative feedback Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Growth Hormone (GH) or Somatotropin • Produced by somatotropic cells of the anterior lobe that: • Stimulate most cells, but target bone and skeletal muscle to increase mass • Promote protein synthesis and encourage the use of fats for fuel • Most effects are mediated indirectly by somatomedins • GH is a peptide hormone- 191 amino acids Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Growth Hormone (GH) • Antagonistic hypothalamic hormones regulate GH • Growth hormone–releasing hormone (GHRH) stimulates GH release- aka Somatoliberin or Somatocrinin • Growth hormone–inhibiting hormone (GHIH) inhibits GH release- aka Somatostatin Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Metabolic Action of Growth Hormone • GH stimulates liver, skeletal muscle, bone, and cartilage to produce insulin-like growth factors • Direct action promotes lipolysis and inhibits glucose uptake Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Metabolic Action of Growth Hormone Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 16. 6

Multiple Hormones Can Target a Cell/Tissue • Growth H • Somatomedins • Thyroxin • All have receptors on many tissues • Stimulate pathways for growth Figure 7 -17: A complex endocrine pathway Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

More Impacts on Target Cells • Synergism: multiple stimuli more than additive • Cortisol +5 • Glucagon +10 • Epinephrine +20 (added = +35) • Synergistic effect + 140 • Antagonism: Two hormones opposing each other in their function, ie. glucagon opposes insulin • Permissiveness: need 2 nd hormone to get full expression, ie. one hormone enhances target organ’s response to a second hormone that is secreted later Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

More Impacts on Target Cells Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 7 -18: Synergism

Permissive Actions of Thyroid Hormone • Thyroxin (T 4) is needed for the function of epinephrine in fatty acid release since Thyroxin induces synthesis of epinephrine receptor • Thyroid hormone is also Permissive (needed) for GH secretion and action Permissive (needed) for development of central nervous system Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Pathologies: Over or Under Production • "no bad hormones – just too much or too little" • Exogenous medication • Replaces & exceeds normal • Cause atrophy of gland • Hypersecretion: too much • Tumors or cancer • Grave's disease- thyroxin • Hyposecretion: too little • Goiter – thyroxin • Diabetes – insulin Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Thyroid Stimulating Hormone (Thyrotropin) • Tropic hormone that stimulates the normal development and secretory activity of the thyroid gland • Triggered by hypothalamic peptide thyrotropinreleasing hormone (TRH) • Rising blood levels of thyroid hormones act on the pituitary and hypothalamus to block the release of TSH Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Adrenocorticotropic Hormone (Corticotropin) • Stimulates the adrenal cortex to release corticosteroids • Triggered by hypothalamic corticotropin-releasing hormone (CRH) in a daily rhythm • Internal and external factors such as fever, hypoglycemia, and stressors can trigger the release of CRH Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Adrenal (Suprarenal) Glands • Adrenal glands – paired, pyramid-shaped organs atop the kidneys • Structurally and functionally, they are two glands in one • Adrenal medulla – nervous tissue that acts as part of the SNS • Adrenal cortex – glandular tissue derived from embryonic mesoderm Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Adrenal Cortex Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 16. 12 a

Adrenal Cortex • Synthesizes and releases steroid hormones called corticosteroids • Different corticosteroids are produced in each of the three layers • Zona glomerulosa – mineralocorticoids (chiefly aldosterone) • Zona fasciculata – glucocorticoids (chiefly cortisol) • Zona reticularis – gonadocorticoids (chiefly androgens) Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Mineralocorticoids • Regulate the electrolyte concentrations of extracellular fluids • Aldosterone – most important mineralocorticoid • Maintains Na+ balance by reducing excretion of sodium from the body • Stimulates reabsorption of Na+ by the kidneys Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Glucocorticoids (Cortisol) • Help the body resist stress by: • Keeping blood sugar levels relatively constant • Maintaining blood volume and preventing water shift into tissue • Cortisol provokes: • Gluconeogenesis (formation of glucose from noncarbohydrates) • Rises in blood glucose, fatty acids, and amino acids Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Excessive Levels of Glucocorticoids • Excessive levels of glucocorticoids: • Depress cartilage and bone formation • Inhibit inflammation • Depress the immune system • Promote changes in cardiovascular, neural, and gastrointestinal function Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Gonadocorticoids (Sex Hormones) • Most gonadocorticoids secreted are androgens (male sex hormones), and the most important one is testosterone • Androgens contribute to: • The onset of puberty • The appearance of secondary sex characteristics • Sex drive in females • Androgens can be converted into estrogens after menopause Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Adrenal Medulla • Made up of chromaffin cells that secrete epinephrine and norepinephrine • Secretion of these hormones causes: • Blood glucose levels to rise • Blood vessels to constrict • The heart to beat faster • Blood to be diverted to the brain, heart, and skeletal muscle Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Adrenal Medulla • Epinephrine is the more potent stimulator of the heart and metabolic activities • Norepinephrine is more influential on peripheral vasoconstriction and blood pressure Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Stress and the Adrenal Gland Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 16. 15

Symptoms of Cushing’s • Facial redness • Rounding of the face (moon face) • Unexplained weight gain around belly • Buffalo hump, or hump on back of neck • Pink or purple stretch marks • Thicker or more visible body and facial hair • Acne • Muscle weakness • Extreme fatigue • Thin and fragile skin that bruises easily • Depression, anxiety and irritability • Slow healing of cuts, insect bites and infections • Bone thinning • Recurrent infections • Sleep disturbances, night sweats, awake at midnight or 4 am • High blood pressure • Diabetes mellitus • Irregular or absent menstrual periods in females Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Cushing’s Syndrome Clinical features • • General • • • • Central obesity Proximal muscle weakness HTN Headaches Dermatologic • • • Wide purple striae Spontaneous ecchymoses Facial plethora Hyperpigmentation Acne, hirsutism Fungal skin infections Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Endocrine/Metabolic • Hypokalemic alkalosis Hypokalemia Osteopenia Hypogonadism Glucose intolerance Hyperlipidemia Hyperhomocysteinemia Kidney stones Polyuria Hypercoagulability Neuropsychiatric • • • Insomnia Depression, frank psychosis Impaired cognition and short-term memory

Cushing’s Syndrome Clinical features Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Presentation Weight Gain Glucose Intolerance HTN Hypokalemia Infections Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Pathologies: Over or Under Production Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 7 -19: Negative feedback by exogenous cortisol

Gonadotropins • Gonadotropins – follicle-stimulating hormone (FSH) and luteinizing hormone (LH) • Regulate the function of the ovaries and testes • FSH stimulates gamete (egg or sperm) production • Absent from the blood in prepubertal boys and girls • Triggered by the hypothalamic gonadotropinreleasing hormone (Gn. RH) during and after puberty Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Gonads: Female • Paired ovaries in the abdominopelvic cavity produce estrogens and progesterone • They are responsible for: • Maturation of the reproductive organs • Appearance of secondary sexual characteristics • Breast development and cyclic changes in the uterine mucosa Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Functions of Gonadotropins • In females • LH works with FSH to cause maturation of the ovarian follicle • LH works alone to trigger ovulation (expulsion of the egg from the follicle) • LH promotes synthesis and release of estrogens and progesterone Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Gonads: Male • Testes located in an extra-abdominal sac (scrotum) produce testosterone • Testosterone: • Initiates maturation of male reproductive organs • Causes appearance of secondary sexual characteristics and sex drive • Is necessary for sperm production • Maintains sex organs in their functional state Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Functions of Gonadotropins • In males • LH stimulates interstitial cells of the testes to produce testosterone • LH is also referred to as interstitial cellstimulating hormone (ICSH) Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Prolactin (PRL) • In females, stimulates milk production by the breasts • Triggered by the hypothalamic prolactin-releasing hormone (PRH) • Inhibited by prolactin-inhibiting hormone (PIH) • Blood levels rise toward the end of pregnancy • Suckling stimulates PRH release and encourages continued milk production Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Pathologies: Due to Receptors • Downregulation – hyperinsulinemia • Transduction abnormalities • Testicular feminization syndrome: Cause by a defective receptor for Testosterone • Pseudohypoparathyroidism: caused by defective G Protein Signal Transduction • Abnormalities of control mechanisms Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Pathologies: Primary and Secondary Hypersecretion Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 7 -20: Primary and secondary hypersecretion of cortisol

Pineal Gland • Small gland hanging from the roof of the third ventricle of the brain • Secretory product is melatonin • Melatonin is involved with: • Day/night cycles • Physiological processes that show rhythmic variations (body temperature, sleep, appetite) Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Pineal Gland Melatonin Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 7 -22 -1: The pineal gland

Circadian Clock Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Pineal Gland Melatonin • Melatonin: Influences body clock & antioxidant activity • Other roles need research: SAD (Seasonal Affective Disorder) & sexual behavior (? ) Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Pineal Gland Melatonin Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 7 -22 -2: The pineal gland

Recommendations for Jet Lag Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Summary • Endocrine glands throughout body are key to chemical integration and homeostasis • Protein, polypeptide, amine and a few steroid hormones are plasma soluble and target membrane • Surface receptors transduce signals into cell and activate via second messengers • Most steroid and some amine hormones are lipophilic, can pass into cell, bind on cytoplasmic or nuclear receptors and activate DNA for protein synthesis • Hypothalamus, pituitary trophic hormone pathways coordinate endocrine regulation Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings