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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

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chapter 23
Chapter 23
  • Adrenal glands
  • Thyroid hormones
  • Growth hormone
  • Tissue and bone growth
  • Calcium balance
review of endocrine principles
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
Adrenal Glands

Structure and function of the adrenal gland

Figure 23-1a

adrenal glands1
Adrenal Glands

Figure 23-1c

adrenal cortex secretes steroid hormones
Adrenal Cortex Secretes Steroid Hormones
  • Aldosterone (Mineralcorticoid)
  • Glucocorticoids
    • Cortisol
  • Sex Hormones
adrenal glucocorticoids1
Adrenal Glucocorticoids

Synthesis pathways for steroid hormones

Figure 23-2

cortisol
Cortisol

The HPA pathway for the control of cortisol secretion

Corticotropin Releasing Hormone

Adrenocorticotropic Hormone

Figure 23-3

cortisol2
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
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

Hypercortisolism: Excess cortisol in the body

Cushings 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
hypercortisolism1
Hypercortisolism

Figure 23-5

hypocortisolism
Hypocortisolism
  • Less common than Cushing’s syndrome
  • Addison’s disease
    • Hyposecretion of all adrenal steroid hormones
    • Autoimmune destruction of adrenal cortex
thyroid structure
Thyroid: Structure

Figure 23-7a

thyroid structure1
Thyroid: Structure

Figure 23-7b

thyroid
Thyroid

Thyroid hormones are made from iodine and tyrosine

Figure 23-8

hyperthyroidism
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
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
thyroid2
Thyroid

A man with goiter due to excessive TSH stimulation

Figure 23-13

thyroid3
Thyroid

Goiter can occur in both hyperthyroidism and hypothyroidism

Figure 23-14a

thyroid4
Thyroid

Figure 23-14b

normal growth
Normal Growth
  • Growth hormone and other hormones
  • An adequate diet
  • Absence of stress
  • Genetics
growth hormone1
Growth Hormone
  • Severe GH deficiency leads to dwarfism
  • Oversecretion of GH in children leads to giantism
  • Oversecretion of GH in adults leads to acromegaly
bone growth
Bone growth

Epiphysis

is the end

of a long

bone.

Diaphysis

is the

shaft of a

long bone.

Bone

gr

owth

Compact

bone

Dividing

chondrocytes

add length

to bone.

Epiphyseal plate is the

site of bone growth.

Chondrocyte

Direction of growth

Chondrocytes

produce

cartilage.

Old

chondrocytes

disintegrate.

Cartilage

Osteoblasts lay

down bone on

top of cartilage.

Diaphysis

Newly calcified

bone

Osteoblast

Linear growth of long bones takes place at the epiphyseal plates

Figure 23-19

bone growth1
Bone growth

Epiphysis

is the end

of a long

bone.

Diaphysis

is the

shaft of a

long bone.

Epiphyseal plate is the

site of bone growth.

Diaphysis

Figure 23-19 (1 of 5)

bone growth2
Bone growth

Epiphysis

is the end

of a long

bone.

Diaphysis

is the

shaft of a

long bone.

Compact

bone

Dividing

chondrocytes

add length

to bone.

Epiphyseal plate is the

site of bone growth.

Chondrocyte

Diaphysis

Figure 23-19 (2 of 5)

bone growth3
Bone growth

Epiphysis

is the end

of a long

bone.

Diaphysis

is the

shaft of a

long bone.

Compact

bone

Dividing

chondrocytes

add length

to bone.

Epiphyseal plate is the

site of bone growth.

Chondrocyte

Chondrocytes

produce

cartilage.

Cartilage

Diaphysis

Figure 23-19 (3 of 5)

bone growth4
Bone growth

Epiphysis

is the end

of a long

bone.

Diaphysis

is the

shaft of a

long bone.

Compact

bone

Dividing

chondrocytes

add length

to bone.

Epiphyseal plate is the

site of bone growth.

Chondrocyte

Chondrocytes

produce

cartilage.

Old

chondrocytes

disintegrate.

Cartilage

Diaphysis

Figure 23-19 (4 of 5)

bone growth5
Bone growth

Epiphysis

is the end

of a long

bone.

Diaphysis

is the

shaft of a

long bone.

Bone

gr

owth

Compact

bone

Dividing

chondrocytes

add length

to bone.

Epiphyseal plate is the

site of bone growth.

Chondrocyte

Direction of growth

Chondrocytes

produce

cartilage.

Old

chondrocytes

disintegrate.

Cartilage

Osteoblasts lay

down bone on

top of cartilage.

Diaphysis

Newly calcified

bone

Osteoblast

Figure 23-19 (5 of 5)

calcium
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
Calcium Balance in the Body

Small intestine

Dietary

calcium

Calcium

in feces

Ca2+

Calcitrol

(PTH, prolactin)

Some calcium is secreted

into the small intestine.

ECF

Bone

Kidney

Passive

filtration

Calcitonin

[Ca2+]

Ca2+ in

kidney

tubules

Ca2+

2.5 mM

PTH

PTH

Calcitriol

Calcitonin

Cortisol

Electrochemical

gradient

Active

transport

Cells

[free Ca2+]

0.001 mM

KEY

Ca2+

in urine

PTH = parathyroid

hormone

Figure 23-20

calcium balance in the body1
Calcium Balance in the Body

ECF

[Ca2+]

2.5 mM

KEY

PTH = parathyroid

hormone

Figure 23-20 (1 of 5)

calcium balance in the body2
Calcium Balance in the Body

ECF

[Ca2+]

2.5 mM

Electrochemical

gradient

Active

transport

Cells

[free Ca2+]

0.001 mM

KEY

PTH = parathyroid

hormone

Figure 23-20 (2 of 5)

calcium balance in the body3
Calcium Balance in the Body

ECF

Bone

Calcitonin

[Ca2+]

Ca2+

2.5 mM

PTH

Calcitriol

Cortisol

Electrochemical

gradient

Active

transport

Cells

[free Ca2+]

0.001 mM

KEY

PTH = parathyroid

hormone

Figure 23-20 (3 of 5)

calcium balance in the body4
Calcium Balance in the Body

Small intestine

Dietary

calcium

Ca2+

Calcitrol

(PTH, prolactin)

ECF

Bone

Calcitonin

[Ca2+]

Ca2+

2.5 mM

PTH

Calcitriol

Cortisol

Electrochemical

gradient

Active

transport

Cells

[free Ca2+]

0.001 mM

KEY

PTH = parathyroid

hormone

Figure 23-20 (4 of 5)

calcium balance in the body5
Calcium Balance in the Body

Small intestine

Dietary

calcium

Calcium

in feces

Ca2+

Calcitrol

(PTH, prolactin)

Some calcium is secreted

into the small intestine.

ECF

Bone

Kidney

Passive

filtration

Calcitonin

[Ca2+]

Ca2+ in

kidney

tubules

Ca2+

2.5 mM

PTH

PTH

Vitamin D

Calcitonin

Cortisol

Electrochemical

gradient

Active

transport

Cells

[free Ca2+]

0.001 mM

KEY

Ca2+

in urine

PTH = parathyroid

hormone

Total body calcium = intake  output

Figure 23-20 (5 of 5)

calcium balance1
Calcium Balance

Osteoclasts are responsible for bone resorption

Figure 23-21

calcium balance2
Calcium Balance
  • Parathyroid hormone
    • Mobilizes calcium from bone
    • Enhances renal reabsorption
    • Indirectly increases intestinal absorption
  • Vitamin D (Calcitriol)
  • Calcitonin (from Thyroid)
osteoporosis
Osteoporosis

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

Figure 23-24