55 - Pituitary Function and Failure

Question 1

Link between the hypothalamus and the pituitary gland

Answer 1

Vascular (anterior) and neural (posterior)

Question 2

Advantages of hormones in the hypothalamic-hypophyseal portal system over hormones released into general circulation

Answer 2

Less hormone secretion to elicit a given level of response

Question 3

Posterior pituitary gland

Answer 3

Outgrowth of the brain and nervous tissue

Neural link to the hypothalamus

Question 4

Anterior pituitary gland

Answer 4

Origin from glandular epithelial tissue, ectodermal cells

Vascular link to hypothalamus

Question 5

True endocrine gland of the pituitary

Answer 5

Anterior pituitary gland

Question 6

Relationship between hypothalamus and pituitary

Answer 6

Hypothalamus stimulates pituitary, which releases hormones

Question 7

Examples of things released by posterior pituitary gland

Answer 7

Vasopressin/ADH (increase collecting duct permeability, decrease urine volume)

Oxytocin (breasts - milk ejection, uterus - contraction)

Question 8

Synthesis and storage of oxytocin

Answer 8

Synthesised in hypothalamus.
Vesicles containing oxytocin are transported to posterior pituitary, and stored here.
When needed, released into veins of general circulation

Question 9

Hypothalamic-hypophyseal portal system
1
2
3
4

Answer 9

Vascular system connecting hypothalamus to anterior pituitary.

Neurons synthesise trophic hormones, release neurohormones into capillaries of portal system.

Portal vessels carry trophic hormones directly to anterior pituitary.

Endocrine cells (of anterior pituitary) release hormones into general circulation, upon stimulation by trophic hormones.

Question 10

Cortisol release
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2
3

Answer 10

Hypothalamus releases corticotrophin releasing hormone
Anterior pituitary releases adrenocorticotropic hormone
Adrenal cortex releases Cortisol

Question 11

Role of prolactin

Answer 11

Increases size of mammary glands.

Breast growth, milk secretion

Question 12

Roles of LH and FSH

Answer 12

Stimulate gonads (ovaries in females, testes in males) to release oestrogen and progesterone in females, testosterone in males.

Also stimulate gamete production (ova in females, sperm in males)

Question 13

Kallman syndrome
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2
3

Answer 13

– Embryologically GnRH (gonadotropin-releasing hormone) neurons failed to migrate via olfactory pathway
– Hypogonadotropic hypogonadism
– Hyposmia or anosmia (loss of smell)

Question 14

Role of parathyroid gland

Answer 14

Calcium metabolism

Question 15

Essential hormonal requirement for growth

Answer 15

Growth hormone (somatotropin)

Question 16

Amount of brain growth within first two years of life

Answer 16

70% increase in size

Question 17

Release of somatomedins (IGF)

Answer 17

Hypothalamus produces somatocrinin (stimulates somatotropin release) and somatostatin (inhibits somatotropin release)

Anterior pituitary produces somatotropin

Liver releases somatomedin

Question 18

Another name for somatostatin

Answer 18

Growth hormone-inhibiting hormone

Question 19

Another name for somatotropin

Answer 19

Growth hormone

Question 20

Effects of growth hormone
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2
3

Answer 20

• Metabolic effects
– Increase blood fatty acid and glucose – anti insulin
– during prolonged fasting or when body’s energy
needs exceeded

• Soft tissues and skeleton
– hyperplasia and hypertrophy on soft tissues &
skeleton
– Increased protein synthesis

• Increased IGFs from liver

Question 21

Type of hormone that GH is

Answer 21

Peptide

Question 22

Circulation of GH

Answer 22

Half dissolve din plasma, half bound to a binding protein, structure of which is identical to GH-R

Question 23

Factors affecting release of GH

Answer 23

Circadian rhythm of tonic secretion.

Influenced by circulating nutrients, stress, other hormones

Question 24

Target cells or tissues of GH

Answer 24

Trophic on liver for IGF release, acts directly on many cells

Question 25

GH receptor

Answer 25

Tyrosine kinase receptor on cell surface

Question 26

GH effect (whole body)

Answer 26

Bone, cartilage growth
Soft tissue growth
Increased plasma glucose

Question 27

Regulation of GH release

Answer 27

GHRH released from hypothalamus (stimulatory)
Somatostatin released by hypothalamus (inhibitory)
Whichever one is in excess makes GH be released or not.

Question 28

Negative feedback for GH release

Answer 28

IGFs inhibit anterior pituitary from releasing GH.

IGFs inhibit GHRH release from hypothalamus

Question 29

Hormones and paracrines involved in bone growth
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2
3
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5

Answer 29

Tissue growth requires hormones & paracrines
– GH and IGFs required for protein and cell division
– Thyroid hormone plays permissive role
– Insulin supports tissue growth
– Estrogen close epiphyseal plates of long bones
– Bone growth requires calcium

Question 30

Role of oestrogen in bone growth

Answer 30

Causes growth plate to fuse (ends bone growth)

Question 31

What can lead to dwarfism

Answer 31

Decreased GH as a child

Question 32

What is Laron dwarfism?

Answer 32

Normal amount of GH, GH receptors are unresponsive.

Question 33

Effect of overproduction of GH

Answer 33

Gigantism (overproduction of GH before puberty)

Acromegaly (overproduction of GH in an adult)

Question 34

Acromegaly

Answer 34

Overproduction of GH in an adult
Bone and soft tissue deformities
Increased visera size & protein content