II. Characterize Selected Glands ! Hypothalamus ! Pituitary gland ! Growth Hormone

! Thyroid gland ! Parathyroid glands ! Adrenal glands ! Pancreas ! Gonads ! Pineal Gland

! Location ! Anatomy/Histology ! Regulation !Hormonal, humoral,

nervous ! Hormones ! Functions !Target cell & actions

on target cells ! Diseases

(homeostatic imbalances) 49

50

Characterize the hypothalamus gland:

! Master endocrine gland

(along w/

pituitary)

! Location

! Functions

! Hypophyseal portal system

Hypothalamus: Master Controller

of Endocrine System

! Hypothalamus secretes regulatory (releasing) hormones that travel through the hypothalamo-hypophyseal portal system to the anterior pituitary and release

! Tropic (stimulating) hormones from the anterior pituitary that travel in the general circulation to other glands in the body and stimulate

! The secretion of hormones from those glands. ! Hypothalamus " anterior pituitary " glands in body

Fig. 17.14 p. 671

Hypothalamus " anterior pituitary " glands in body

Releasing hormones: TRH, PRH, GnRH, CRH, GHRH Inhibiting hormones: PIH, GIH

Regulatory hormones of hypothalamus Tropic hormones of anterior pituitary

Thyroid-stimulating hormone (TSH) stimulates thyroid gland to release thyroid hormone.

Anterior pituitary Posterior pituitary

Infundibulum

Muscle

Prolactin (PRL) acts on mammary glands to stimulate milk production.

Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) act on gonads (testes and ovaries) to stimulate development of gametes (sperm and oocyte).

Testis Ovary

Thyroid

Mammary gland

TSH Growth hormone (GH) acts on all body tissues, especially cartilage, bone, muscle, and adipose connective tissue to stimulate growth.

Adipose connective tissue

Bone

Adrenal cortex

Adrenocorticotropic hormone (ACTH) acts on the adrenal cortex to cause release of corticosteroids (e.g., cortisol).

Adrenal gland

FSH and LH

GH

ACTH

Hypothalamus

PRL

53

Names & functions of hormones produced by the hypothalamus:

Table 17.3 p. 670

54

Characterize the pituitary gland: ! Anatomy

! Infundibulum ! 2 Lobes/3 Sections:

! Anterior pituitary (adenohypophysis)

! Posterior pituitary (neurohypophysis)

! Intermedia

55

56

Name & Function of Adenohypophyseal (Anterior Pituitary) hormones:

! HM of anterior pituitary controlled by releasing or inhibiting HM produced by hypothalamus

-TSH

-PRL

-FSH

-LH

-ACTH

-GH

-MSH

Hormone Function

Melanocyte-stimulating hormone (MSH) stimulates synthesis of melanin and distribution of melanocytes in skin (little effect in humans)

Table 17.4 p. 672

Mnemonic Device

Page 672

Discussion of Pituitary Hormone Effects

1. Growth Hormones effects on multiple organ systems

2. posterior pituitary hormones (ADH & oxytocin)

3. The effects of other anterior pituitary hormones will be discussed with the particular gland they effect.

Nutrient Metabolism is altered by many hormones, including GH

61

Effects of anterior pituitary human growth hormone & insulinlike growth factors:

! GH promotes secretion of Insulinlike Growth Factors (IGFs)

! Indirect functions of GH via IGFs ! target cells = liver, skeletal muscle, cartilage & bone ! increases cell growth & division ! stimulate lipolysis ! retard use of glucose for ATP production

62

Metabolic action of GH:

Describe the regulation of GH: ! Antagonistic hypothalamic

HM regulate GH ! GHRH stimulates GH

release ! GIH (aka GHIH) inhibits GH

release

! Hypoglycemia stimulates release of GHRH from hypothalamus

! Hyperglycemia & high levels of GH/IGFs ! Inhibit GHRH & GH release ! Stimulate GIH release

What Stimulates

GHRH Secretion?

3 3 4

7 8

5 6

6

Growth hormone

Stimulation Inhibition STIMULUS

Variables that influence the release of GHRH from the hypothalamus:

Age

Nutrient levels in the blood Stress and exercise

Time of day

Hypothalamus

CONTROL CENTER RECEPTOR

Increased levels of both GH and IGF inhibit the release of GHRH from the hypothalamus; Increased levels of GH also inhibits the release of GH from the anterior pituitary.

NET EFFECT

Increased protein synthesis, mitosis, and cell differentiationespecially in cartilage, bone, and muscle; release of stored nutrients into the blood.

Amino acids

Bone Muscle

EFFECTORS: Effectors respond to GH and/or IGF in the following ways:

Increased growth Increased amino acid uptake which results in protein synthesis Stimulated mitosis

Cell differentiation

Increased lipolysis

Decreased lipogenesis

Increased glycogenolysis and gluconeogenesis Decreased glycogenesis

Adipose connective tissue

Liver tissue

In response to GHRH, the anterior pituitary releases growth hormone (GH).

GH stimulates hepatocytes to release insulin-like growth factor (IGF) into the blood.

Both GH and IGF stimulate target cells (effectors).

The hypothalamus releases growth hormonereleasing hormone (GHRH) into the hypothalamo-hypophyseal portal system.

The hypothalamus responds to various stimuli.

GH

IGF

GH

GH

IGF

Hepatocytes

Liver

GH

Glycerol Fatty acids Glucose

All cells

GHRH

GH

5 4

IGF

2 2 1

1 Good Summary: Fig. 17.15 on p. 674

66

What are the effects of excess growth hormone?

! Diabetogenic effect of GH

67

Clinical Applications:

! Hyposecretion hGH ! childhood = Hypopituitary

dwarfism

! Hypersecretion hGH ! childhood = giantism ! adult = acromegaly

http://www.chauvet-translation.com/figures/Figure027.jpg

Jyoti Amge Smallest girl in the world

Pituitary dwarfism is a condition that exists at birth as a result of inadequate growth hormone production due to a hypothalamic or pituitary problem. Growth retardation is typically not evident until a child reaches 1 year of age, because the influence of growth hormone (GH) is minimal during the first 6 to 12 months of life. In addition to short stature, children with pituitary dwarfism often have periodic low blood sugar (hypoglycemia). Injections of growth hormone over a period of many years can bring about improvement, but not a normal state. Too much growth hormone causes excessive growth and leads to increased levels of blood sugar. Oversecretion of growth hormone in childhood causes pituitary gigantism. Beyond extraordinary height (sometimes up to 8 feet), these people have enormous internal organs, a large and protruding tongue, and significant problems with blood glucose management. If untreated, a pituitary giant dies at a comparatively early age, often from complications of diabetes or heart failure.

leads to a protruding jaw (prognathism). Internal organs, especially the liver, increase in size, and increased release of glucose lead to the development of diabetes in virtually everyone with acromegaly. Acromegaly may result from loss of feedback control of growth hormone at either the hypothalamic or pituitary level, or it may develop because of a GH-secreting tumor of the pituitary. Removal of the pituitary alleviates the effects of acromegaly, but this drastic treatment results in the loss of all pituitary hormones.

Pituitary dwarfism

Gigantism

Age 52

Age 16 Age 9

Age 33 Acromegaly

CLINICAL VIEW Disorders of Growth Hormone Secretion

INTEGRATE

Excessive growth hor- mone production in an adult results in acromegaly. The individual does not grow in height, but the bones of the face, hands, and feet enlarge and widen (appositional growth), along with growth in cartilage. An increase in mandible size

69

Characterize the posterior pituitary gland (neurohypophysis)

! Hypothalamo-hypophyseal tract ! Axon terminals of

hypothalamic neurons

! No hormone synthesis ! Stores/releases

ADH & oxytocin

70

Characterize oxytocin:

! Two target tissues: ! Both involved in

neuroendocrine reflexes

! During delivery = uterus ! After delivery = breasts

71

Recall the function of antidiuretic hormone (ADH) aka vasopressin

! decrease urine production

! decrease sweating

! increase BP

Describe the regulation of

ADH: ! ADH released when

blood osmotic pressure

is high (dehydration or

blood loss)

! ADH inhibited when blood osmotic pressure

is low (increased blood

volume)

74

Clinical Application: ! Central or pituitary diabetes insipidus

! kidneys are unable to conserve water

! Etiology damage to hypothalamus or pituitary

! Sx excessive thirst & urination

75

Characterize the thyroid gland: ! Location

! 2 lobes either side of trachea ! Connected by isthmus

! Functions

76

Describe the histology of

thyroid gland:

! Consists of follicles ! Follicular cells ! Thyroglobulin ! T3 & T4

! Parafollicular cells ! Calcitonin

Functions of T3 & T4 ! Increase BMR (basal

metabolic rate)

! Stimulate protein synthesis

! Increase use of glucose & fatty acids for ATP production

! Heat production ! Regulating tissue growth # Developing skeletal & nervous systems

Functions Calcitonin ! Parafollicular cells or C cells produce calcitonin

! peptide HM ! Lowers blood Ca2+ by inhibiting bone

resorption ! Inhibits osteoclast activity (& thus bone

resorption) & release of Ca+2 from bone matrix

! Stimulates Ca+2 uptake & incorporation into bone matrix

! Antagonist to parathyroid hormone (PTH)

Mechanism of Thyroid

Hormone Production

Know Figure 17.18

80

Low blood levels of T3 and T3 or low metabolic rate stimulate release of

Hypothalamus TRH

Actions of Thyroid Hormones:

Increase basal metabolic rate Stimulate synthesis of Na+/K+ ATPase

Increase body temperature (calorigenic effect) Stimulate protein synthesis

Increase the use of glucose and fatty acids for ATP production Stimulate lipolysis

Enhance some actions of catecholamines Regulate development and growth of nervous tissue and bones

1

Anterior pituitary

TRH, carried by hypophyseal portal veins to

anterior pituitary, stimulates

release of TSH by thyrotrophs

Low blood levels of T3 and T3 or low metabolic rate stimulate release of

Hypothalamus

TSH

TRH

Actions of Thyroid Hormones:

Increase basal metabolic rate Stimulate synthesis of Na+/K+ ATPase

Increase body temperature (calorigenic effect) Stimulate protein synthesis

Increase the use of glucose and fatty acids for ATP production Stimulate lipolysis

Enhance some actions of catecholamines Regulate development and growth of nervous tissue and bones

1

2

Anterior pituitary

TRH, carried by hypophyseal portal veins to

anterior pituitary, stimulates

release of TSH by thyrotrophs

TSH released into blood stimulates

thyroid follicular cells

Thyroid follicle

Low blood levels of T3 and T3 or low metabolic rate stimulate release of

Hypothalamus

Anterior pituitary

TSH

TRH

Actions of Thyroid Hormones:

Increase basal metabolic rate Stimulate synthesis of Na+/K+ ATPase

Increase body temperature (calorigenic effect) Stimulate protein synthesis

Increase the use of glucose and fatty acids for ATP production Stimulate lipolysis

Enhance some actions of catecholamines Regulate development and growth of nervous tissue and bones

1

2

3

T3 and T4 released into

blood by follicular cells

TRH, carried by hypophyseal portal veins to

anterior pituitary, stimulates

release of TSH by thyrotrophs

TSH released into blood stimulates

thyroid follicular cells

Thyroid follicle

Low blood levels of T3 and T3 or low metabolic rate stimulate release of

Hypothalamus

Anterior pituitary

TSH

TRH

Actions of Thyroid Hormones:

Increase basal metabolic rate Stimulate synthesis of Na+/K+ ATPase

Increase body temperature (calorigenic effect) Stimulate protein synthesis

Increase the use of glucose and fatty acids for ATP production Stimulate lipolysis

Enhance some actions of catecholamines Regulate development and growth of nervous tissue and bones

1

2

3

4 T3 and T4 released into

blood by follicular cells

Elevated T3inhibits release of TRH and

TSH (negative feedback)

TRH, carried by hypophyseal portal veins to

anterior pituitary, stimulates

release of TSH by thyrotrophs

TSH released into blood stimulates

thyroid follicular cells

Thyroid follicle

Low blood levels of T3 and T3 or low metabolic rate stimulate release of

Hypothalamus

Anterior pituitary

TSH

TRH

Actions of Thyroid Hormones:

Increase basal metabolic rate Stimulate synthesis of Na+/K+ ATPase

Increase body temperature (calorigenic effect) Stimulate protein synthesis

Increase the use of glucose and fatty acids for ATP production Stimulate lipolysis

Enhance some actions of catecholamines Regulate development and growth of nervous tissue and bones

1

2

3

5

4

T3 & T4 Secretion Regulation

! Hypothalamus secretes TRH in response to

blood levels of T3 & T4

! TRH # secretion of TSH from anterior pituitary

! TSH stimulates synthesis/secretion of T3 & T4

Good Summary

Figure 17.19

82

Clinical Application: Thyroid Gland Disorders ! Hypothyroidism

! Congential # Cretinism ! Adult # Myxedema

83

Clinical Application: Thyroid Gland Disorders

! Hyperthyroidism (Graves disease)

! Goiter = enlarged thyroid (dietary)

Page 678

85

Characterize the parathyroid glands: ! 4 glands embedded in

lobes of thyroid gland ! Chief (Principal) cells ! Oxyphil cells

86

Describe the mechanism of action of PTH:

! Parathyroid hormone (PTH) or parathormone ! Major regulator of Ca+2,

Mg, & phosphate ions in blood

! Increases number & activity of osteoclasts

! Elevates bone resorption

! Blood Ca+2 level directly controls secretion of both calcitonin & PTH via (-) feedback

87

Parathyroid Hormones

Blood Calcium Regulation

90

Clinical Application: Hyperparathyroidism

! Parathyroid adenoma #1 cause ! Serum calcium imbalance