Chapter 12: The Endocrine System: Glands and Hormones

Table 12-1: The Endocrine Glands and Their Hormones

• Hypothalamus

  • Releasing hormones: Control the release of anterior pituitary hormones

  • ADH (antidiuretic hormone): Promotes water reabsorption in kidney tubules; stimulates constriction of blood vessels

  • Oxytocin: Causes uterine muscle contraction; causes milk ejection from mammary glands

• Anterior pituitary

  • GH (growth hormone): Promotes growth of all body tissues

  • TSH (thyroid-stimulating hormone): Stimulates thyroid gland to produce thyroid hormones

  • ACTH (adrenocorticotropic hormone): Stimulates adrenal cortex to produce glucocorticoids and androgens

  • PRL (prolactin): Stimulates milk production by mammary glands

  • FSH (follicle-stimulating hormone): Stimulates growth and hormonal activity of ovarian follicles; stimulates growth of testes; promotes sperm cell development

  • LH (luteinizing hormone): Initiates ovulation, corpus luteum formation, and progesterone production in the female; stimulates testosterone secretion in male

• Thyroid

  • Thyroxine (T and triiodothyronine (T3)): Increase metabolic rate, influencing both physical and mental activities; required for normal growth

• Parathyroids

  • PTH (parathyroid hormone): Regulates exchange of calcium between blood and bones; increases calcium level in blood

• Adrenal medulla

  • Epinephrine: Increases blood pressure and heart rate; activates cells influenced by sympathetic nervous system plus many not supplied by sympathetic nerves

• Adrenal cortex

  • Cortisol (95% of glucocorticoids): Increases blood glucose concentration in response to stress

  • Aldosterone (95% of mineralocorticoids): Promotes salt (and thus water) retention and potassium excretion

  • Weak androgens: Contribute to some secondary sex characteristics in women

• Pancreatic islets

  • Insulin: Reduces blood glucose concentrations by promoting glucose uptake into cells and glucose storage; promotes fat and protein synthesis

  • Glucagon: Stimulates the liver to release glucose, thereby increasing blood glucose levels

• Testes

  • Testosterone: Stimulates growth and development of sexual organs (testes and penis) plus development of secondary sexual characteristics, such as hair growth on the body and face and deepening of voice; stimulates sperm cell maturation

• Ovaries

  • Estrogens (e.g., estradiol): Stimulates growth of primary sexual organs (uterus and tubes) and development of secondary sexual organs, such as breasts; stimulates development of ovarian follicles

  • Progesterone: Stimulates development of mammary glands' secretory tissue; prepares uterine lining for implantation of fertilized ovum; aids in maintaining pregnancy

• Pineal

  • Melatonin: Regulates mood, sexual development, and daily cycles in response to the amount of light in the environment

The Endocrine System

• Consists of a group of glands that produce hormones

• Works with the nervous system to control and coordinate all other body systems

• Affects body systems by chemical stimuli

Hormones

• Chemical messengers with regulatory effects on cells or organs

• Hormones from endocrine glands are released directly into tissue fluids, not through ducts

• Some affect many tissues

  • Growth hormone

  • Thyroid hormone (metabolism)

  • Insulin (blood sugar regulation)

• Some affect a specific tissue

  • Thyroid-stimulating hormone (TSH)

  • Adrenocorticotropic hormone (ACTH)

Hormone Chemistry

• Amino acid compounds

  • Proteins or related compounds

  • All hormones except steroids

• Lipids

  • Made of fatty acids

  • Most are steroids, derived from the steroid cholesterol

  • Produced in the adrenal cortex and sex glands

  • Prostaglandins are also lipids

Hormone Regulation

• Negative feedback (most common)

  • Endocrine gland oversecretes hormone

  • Tissue becomes too active

  • Action negatively affects gland to decrease secretion

• Positive feedback

  • Hormone response produces more hormone

The Pituitary

• The "master gland": releases hormones that affect the working of other endocrine glands

• Pituitary structure

  • Anterior lobe

  • Posterior lobe

  • Infundibulum - stalk that connects to hypothalamus

Control of the Pituitary

• Hypothalamus sends releasing hormones (RH) and inhibiting hormones (IH)

• Hormones stimulate and suppress anterior pituitary secretions

• Hypothalamus produces antidiuretic hormone (ADH) and oxytocin

• Stored in the posterior pituitary

• Nerve impulses stimulate secretions

Anterior Pituitary Lobe Hormones

• Growth hormone (GH)

• Thyroid-stimulating hormone (TSH)

• Adrenocorticotropic hormone (ACTH)

• Prolactin (PRL)

• Follicle-stimulating hormone (FSH)

• Luteinizing hormone (LH)

Posterior Pituitary Lobe Hormones

• Antidiuretic hormone (ADH)

• Oxytocin

Pituitary Tumors

• Gigantism - child - abnormally tall

• Acromegaly - adult - large face/hands/feet

The Thyroid

• Lateral lobes on either side of the larynx

• Connecting band (isthmus)

• Enclosed by connective tissue capsule

Thyroid Hormones

• Thyroxine (T4): Principal hormone; increases energy and protein metabolism rate

• Triiodothyronine (T3): Increases energy and protein metabolism rate

• Calcitonin: Regulates calcium metabolism; works with parathyroid hormone and vitamin D

Disorders of the Thyroid Gland

• Goiter

  • Simple - uniform versus nodular (adenomatous) - irregular with tumor

• Hypothyroidism

  • Congenital - failure of thyroid gland to form; lack of physical growth/mental development

  • Hashimoto thyroiditis (adult) autoimmune hypothyroidism; antibodies attack/destroy thyroid tissue

  • Endemic - goiter from lack of iodine

• Hyperthyroidism

  • Graves disease - common form

  • Thyroid storm - untreated hyperthyroidism

The Endocrine Glands and Their Hormones

Parathyroid Glands (Page 20)

• Four glands in posterior capsule of thyroid

• Secrete parathyroid hormone (PTH)

  • Works with calcitonin to regulate calcium metabolism

Disorders of the Parathyroid Glands (Page 21)

• Hyposecretion

  • Tetany: intermittent muscular spasms caused by malfunction of the parathyroid glands and a deficiency of calcium

• Hypersecretion

  • Increased PTH leads to calcium pulled from storage into bloodstream

  • Causes fragile bones that fracture easily

  • Causes kidney stones

The Adrenal Glands (Page 22)

• Two small glands on top of the kidneys

• Each gland has two parts that act as separate glands

  • Medulla (inside)

  • Cortex (outside)

Hormones from the adrenal medulla (Page 24)

• Epinephrine: "fight or flight" hormone

• Glucocorticoids (cortisol): increases blood glucose in response to stress

• Mineralocorticoids (aldosterone): salt/water retention and potassium excretion

• Sex hormones

Disorders of the Adrenal Cortex (Page 25)

• Hyposecretion

  • Addison disease: autoimmune destruction of gland

  • Symptoms: muscle atrophy, weakness, salt/water imbalance

• Hypersecretion

  • Cushing syndrome: high cortisol secretion

  • Symptoms: obese core/moon face, thin skin, muscle weakness, bone loss, elevated blood glucose

The Pancreas (Page 27)

• Structure

  • Acini: secrete digestive enzymes

  • Islets: secrete hormones

• Pancreatic Hormones

  • Insulin: lowers blood sugar level; stimulates manufacture of amino acids into protein

  • Glucagon: increases blood sugar

Diabetes Mellitus (Page 30)

• Most common endocrine disorder

• Types

  • Type 1 diabetes: destruction of insulin-producing cells (juvenile onset)

  • Type 2 diabetes: typically overweight patients; can have decreased insulin or insulin resistance

  • Metabolic syndrome: signs present that patient is likely to develop T2DM or cardiovascular disease

  • Gestational diabetes: during pregnancy

The Sex Glands (Page 31)

• Ovaries and testes produce hormones to develop sexual characteristics and maintain reproductive organs

• Hormones of the testes

  • Androgens (e.g., testosterone)

• Hormones of the ovaries

  • Estrogens

  • Progesterone

The Pineal Gland (Page 32)

• Cone-shaped structure posterior to the midbrain

• Produces melatonin

  • Influences sleep-wake cycles

  • Appears to delay onset of puberty

Prostaglandins (Page 33)

• Group of hormones made by most body tissues

• Produced, act, and rapidly inactivated in or close to origin

• Functions

  • Constrict structures

  • Dilate structures

  • Promote inflammation

Hormones and Treatment (Page 34)

• Hormones are extracted from animal tissue, manufactured in the lab, or genetically engineered

• Examples of hormones

  • Growth hormone

  • Insulin

  • Adrenal steroids

  • Epinephrine (adrenaline)

  • Thyroid hormones

  • Oxytocin

  • Androgens

  • Estrogen and progesterone

Aging and the Endocrine System (Page 35)

• Decline in hormone secretion

• Main clinical conditions

  • Type 2 diabetes mellitus

  • Osteoporosis (related to decrease in estrogen)

Word Anatomy (Page 36-38)

• Definitions of word parts related to endocrine glands and hormones