chapter 23

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Chapter 23

Adrenal glands

Thyroid hormones

Growth hormone

Tissue and bone growth

Calcium balance


Review of Endocrine Principles Hypothalamic-pituitary control system

Several hormones controlled by hypothalamic and anterior pituitary trophic hormones

Feedback patterns Negative feedback:

Simple Pathway-Blood glucose level decreasing shuts off insulin secretion Complex Pathway-use the hypothalamic-pituitary control system, where the

feedback signal may be the hormone itself Hormone receptors

May be on surface or inside the cell Cellular responses

Target cells respond by altering existing proteins or making new proteins Magnitude of target cell response

Depends on number of receptors and amount of active hormone Endocrine pathologies

Excess hormone secretion Inadequate hormone secretion Abnormal target cell response to the hormone


Adrenal Glands

Structure and function of the adrenal gland

Figure 23-1a

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 23-1b

Adrenal Glucocorticoids

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 23-1c

Adrenal Glands


Adrenal Cortex Secretes Steroid Hormones

1. Aldosterone (Mineralcorticoid)

2. Glucocorticoids Cortisol

3. Sex Hormones

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 23-2

Adrenal Glucocorticoids

Synthesis pathways for steroid hormones


Cortisol

The HPA pathway for the control of cortisol secretion

Corticotropin Releasing HormoneCorticotropin Releasing Hormone

Adrenocorticotropic HormoneAdrenocorticotropic Hormone


Circadian Rhythm of Cortisol Secretion


Cortisol


Cortisol

Promotes gluconeogenesis

Causes breakdown of skeletal muscle proteins

Enhances lipolysis

Suppresses the immune system

Causes negative calcium balance

Influences brain function


Cortisol: Therapeutic Drug

Suppresses the immune system

Inhibits the inflammatory response

Used to treat Bee stings, poison ivy, and pollen allergies

Prevents rejection of transplanted organs


Hypercortisolism

Hypercortisolism: Excess cortisol in the bodyCushings Syndrome: Hormonal disorder caused by prolonged

exposure to excess cortisol (including iatrogenic). Signs and Symptoms

Hyperglycemia Muscle protein breakdown Excess deposits of extra fat in trunk and face Thin arms and legs Thin skin and bruising

Three causes of hypercortisolism: Adrenal tumor that autonomously secretes cortisol (Primary

Hypercortisolism) Pituitary tumor that autonomously secretes ACTH (Secondary

Hypercortisolism or Cushing’s Disease) Iatrogenic hypercortisolism


Hypercortisolism


Hypocortisolism

Less common than Cushing’s syndrome

Addison’s disease Hyposecretion of all adrenal steroid hormones

Autoimmune destruction of adrenal cortex


Thyroid: Structure

Figure 23-7a


Thyroid: Structure

Figure 23-7b


Thyroid

Thyroid hormones are made from iodine and tyrosine


Thyroid


Hyperthyroidism

Increases oxygen consumption and metabolic heat production

Increase protein catabolism and may cause muscle weakness

Hyperexcitable reflexes and psychological disturbances

Influence -adrenergic receptors in the heart


Hypothyroidism

Slow metabolic rate and oxygen consumption

Decreases protein synthesis

Slowed reflexes, slow speech and thought processes, and feelings of fatigue Cretinism in infants

Bradycardia


Pathway of Thyroid Hormone Control


Thyroid

A man with goiter due to excessive TSH stimulation

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 23-14a

Thyroid

Goiter can occur in both hyperthyroidism and hypothyroidism

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 23-14b

Thyroid


Normal Growth

Growth hormone and other hormones

An adequate diet

Absence of stress

Genetics


Pathway of Growth Hormone Control


Growth Hormone


Growth Hormone

Severe GH deficiency leads to dwarfism

Oversecretion of GH in children leads to giantism

Oversecretion of GH in adults leads to acromegaly


Three Individuals with Acromegaly


Bone growth

Linear growth of long bones takes place at the epiphyseal plates

Epiphysisis the endof a long

bone.

Diaphysisis the

shaft of along bone.

Epiphyseal plate is thesite of bone growth.

Diaphysis

Compactbone

Osteoblast

Dir

ec

tio

n o

f g

row

th

Chondrocyte

Cartilage

owth

Newly calcifiedbone

Bone gr

Dividingchondrocytes

add lengthto bone.

Chondrocytesproducecartilage.

Oldchondrocytesdisintegrate.

Osteoblasts laydown bone on

top of cartilage.

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 23-19 (1 of 5)

Bone growth


bone.

Diaphysisis the



Diaphysis


Bone growth


bone.

Diaphysisis the



Diaphysis

Compactbone

Chondrocyte


add lengthto bone.


Bone growth


bone.

Diaphysisis the



Diaphysis

Compactbone

Chondrocyte

Cartilage


add lengthto bone.



Bone growth


bone.

Diaphysisis the



Diaphysis

Compactbone

Osteoblast

Dir

ec

tio

n o

f g

row

th

Chondrocyte

Cartilage

owth

Newly calcifiedbone

Bone gr


add lengthto bone.



Osteoblasts laydown bone on

top of cartilage.


Calcium Balance


Calcium

Important signal molecule

Part of intercellular cement that holds cells together at tight junction

Cofactor in the coagulation cascade

Affects the excitability of neurons


Calcium Balance in the Body

Ca2+

Small intestine

Dietarycalcium

Calciumin feces

[free Ca2+]0.001 mM

Kidney

Ca2+

in urine

Ca2+ inkidney tubules

Calcitrol(PTH, prolactin)

Active transport

Some calcium is secreted into the small intestine.

Cells

[Ca2+]

2.5 mM

PassivefiltrationCalcitonin

Ca2+PTH

Calcitonin

PTH

CalcitriolCortisol

Bone ECF

Electrochemicalgradient

PTH = parathyroid hormone

KEY



[Ca2+]

2.5 mM

ECF


KEY



[free Ca2+]0.001 mM

Active transport

Cells

[Ca2+]

2.5 mM

ECF



KEY



[free Ca2+]0.001 mM

Active transport

Cells

[Ca2+]

2.5 mM

Calcitonin

Ca2+PTH

Calcitriol

Cortisol

Bone ECF



KEY



Ca2+

Small intestine

Dietarycalcium

[free Ca2+]0.001 mM


Active transport

Cells

[Ca2+]

2.5 mM

Calcitonin

Ca2+PTH

Calcitriol

Cortisol

Bone ECF



KEY



Total body calcium = intake output

Ca2+

Small intestine

Dietarycalcium

Calciumin feces

[free Ca2+]0.001 mM

Kidney

Ca2+

in urine

Ca2+ inkidney tubules


Active transport

Some calcium is secreted into the small intestine.

Cells

[Ca2+]

2.5 mM

PassivefiltrationCalcitonin

Ca2+PTH

Calcitonin

PTH

Vitamin D

Cortisol

Bone ECF



KEY


Calcium Balance

Osteoclasts are responsible for bone resorption


Calcium Balance

Parathyroid hormone Mobilizes calcium from bone

Enhances renal reabsorption

Indirectly increases intestinal absorption

Vitamin D (Calcitriol)

Calcitonin (from Thyroid)


Calcium Balance: Parathyroid Glands


Calcium Balance


Endocrine Control of Calcium Balance


Calcitonin


Osteoporosis

Normal bone (left) and bone loss in osteoporosis (right)

chapter 23

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