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ENDOCRINOLOGY > 1a The Pituitary Gland > Flashcards

1a The Pituitary Gland Flashcards

1
Q

What is a hormone?

A

a signalling molecule produced by glands that are transported in the bloodstream to target distant organs

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2
Q

What are peptide hormones synthesized as?

A

Prohormones

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3
Q

How are steroid hormones synthesized?

A

In a series of reactions from cholesterol

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4
Q

What is meant by constitutive secretion?

A

Released as soon as they are produced

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5
Q

Which type of hormone shows constitutive secretion?

A

Steroid hormones

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6
Q

Which hormones is secreted by regulatory secretion?

A

Peptide hormones

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7
Q

What is regulatory secretion?

A

When the hormones is stored in a vesicle and has to be triggered to be released

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8
Q

What is the difference in peptide and steroid hormones in terms of receptors?

A

Peptide hormones bind receptors on cell membranes and induce a signal via a secondary messenger system
Steroid hormones bind to intracellular receptors to change gene expression directly

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9
Q

What has to hapen to peptide hormones in order for them to be activated?

A

The pro hormone which is initially secreted has to be cleaved

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10
Q

label diagram

A
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11
Q

What is the name of the bone which the pituitary gland sits in?

A

Sella tursica of sphenoid bone

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12
Q

What is the name of the posterior pituitary?

A

Pars nervosa

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13
Q

What are the three parts of the anterior pituitary?

A

Pars tuberalis
Pars intermedia
Pars distalis

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14
Q

What is directly above the pituitary?

A

The hypothalamus

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15
Q

What is the median eminence?

A

part of the posterior pituitary which has a blood supply in common with the anterior pituitary

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16
Q

What vascularises the anterior pituitary?

A

The hypothalamic-pituitary portal system

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17
Q

What regulates anterior pituitary function?

A

Hypothalamic Parvocellular neurones

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18
Q

Where do hypothalamic parvocellular neurones terminate?

A

The medial eminence

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19
Q

What length are hypothalamic parvocellular neurones?

A

Short

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20
Q

What do the hypothalamic parvocellular neurones release and into where?

A

Release hypothalamic releasing / inhibiting hormones into the capillary plexus of median eminence

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21
Q

what is special about the capillary plexus in the medial eminence?

A

They are leaky meaning so the hormone factors can enter into the hypothalamic-pituitary portal system

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22
Q

What is the name of the anterior pituitary?

A

Adenohypophysis

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23
Q

What is the adenohypophysis derived from?

A

The Rathke Pouch

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24
Q

What are the 5 types of endocrine cells found in the anterior pituitary?

A

Somatotrophs
Gonadotrophs
Corticotrophs
Lactotrophs
Thyrotrophs

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25
Q

Describe the hypothalamo-pituitary portal system

A
  1. Hypothalamic neurosecretory cells terminate at the medial eminence
  2. Release hypothalamic releasing / inhibiting factors into the capillary plexus
  3. The capillary plexus of median eminence is leaky, meaning these factors are able to enter into the portal circulation to the anterior pituitary
  4. These releasing or inhibiting hormones stimulate the release of hormones from anterior pituitary cells
  5. The hormones leave the gland via the blood
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26
Q

What do somatotrophs secrete?

A

Growth hormone (somatotrophin)

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27
Q

What do gonadotrophs secrete?

A

LH and FSH

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28
Q

What do lactotrophs release?

A

Prolactin

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29
Q

What do thyrotrophs secrete?

A

Thyroid stimulating hormone (TSH)

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30
Q

What do corticotrophs release?

A

Adrenocorticotrophic hormone (ACTH)

31
Q

Describe how the production of the thyroid hormone is regulated?

A
  1. The hypothalamic neurosecretory cells release thyrotrophin releasing hormone into the portal circulation
  2. TRH travels to anterior pituitary via portal system
  3. The TRH acts on the thyrotrophs
  4. The thyrotrophs then release thyroid stimulating hormone to stimulate the thyroid to produce thyroxine
32
Q

What is secreted from the hypothalamic neurosecretory cells to stimulate the thyrotrophs?

A

Thyrotrophin releasing hormone

33
Q

What is secreted from the hypothalamic neurosecretory cells to stimulate the somatotrophs?

A

growth hormone releasing hormone

34
Q

What is secreted from the hypothalamic neurosecretory cells to inhibit the somatotrophs?

A

Somatostatin

35
Q

What is secreted from the hypothalamic neurosecretory cells to stimulate the gonadotrophs??

A

Gonadotrophin releasing hormone

36
Q

What is secreted from the hypothalamic neurosecretory cells to inhibit the lactotrophs?

A

Dopamine

37
Q

What is secreted from the hypothalamic neurosecretory cells to stimulate the corticotrophs?

A

Corticotrophin releasing hormone

38
Q

What causes a bilateral hemianopia?

A

Compressing of the optic chiasm due to a pituitary tumour

39
Q

What crosses at the optic chiasm?

A

Optic fibres from the nasal retinae

40
Q

Why do a bilateral hemianopia cause blindness in the right and left temporal visual fields?

A

Light landing on the nasal retina arrives from the peripheral vision, and since the fibres from the nasal retinae cross at the optic chiasm, a tumour will prevent transmission of sensory information from temporal visual fields

41
Q

What is the main target of growth hormone?

A

General body tissues, particularly the liver

42
Q

What is the main target for prolactin?

A

Breasts - lactating women

43
Q

What is the main target for thyroid stimulating hormone?

A

The thyroid

44
Q

What is the main target of the adrenocorticotrophic hormone?

A

The adrenal cortex

45
Q

What is the origin of the adenohypophysis?

A

Epithelial origin

46
Q

mechanism of growth hormone

A

GHRH (hypo) to GH (ant-pit) binds to general body tissues, liver and stomach
Liver causes IGF-1 (adults and children) and IGF-2 (fetus)-> -ve feedback stopping GHRH and increase somatostatin.
Stomach releases chrelin -> increase GH, GHRH and decrease somatostatin

47
Q

What is the origin of the neurohypophysis?

A

Appendage of the hypothalamus (neural)

48
Q

Which two hormones does the posterior pituitary gland store?

A

Oxytocin and Arginine Vasopressin (AVP or anti-diuretic hormone)

49
Q

Where are oxytocin and Arginine Vasopressin made?

A

Made in the hypothalamus

50
Q

What is the name given to neurones which are excited and release AVP or oxytocin into the posterior pituitary

A

Magnocellular neurones

51
Q

What happens to the AVP and oxytocin in the posterior pituitary?

A

They diffuse into the blood capillaries

52
Q

What does Arginine Vasopressin do?

A

Stimulates the reabsorption of water into the blood to make the urine more concentrated

53
Q

Describe how Arginine Vasopressin affects the concentration of urine?

A
  1. AVP binds to V2 receptor
  2. This triggers an intracellular protein cascade resulting in Aquaporin proteins being inserted into the apical membrane of the kidney tubule
  3. This means water molecules can be transported from the apical membrane into the blood stream
  4. This makes the urine more concentrated
54
Q

Which part of the pituitary is involved in the formation of milk?

A

The anterior pituitary

55
Q

Which part of the pituitary is involved in the ejection of milk from lactating breasts?

A

The posterior pituitary

56
Q

Describe how milk is produced in breasts?

A
  1. Baby sucks on nipple
  2. Mechanical stimulation of nipple and surrounding are activates afferent pathways
  3. Signals integrated in the hypothalamus and inhibit dopamine release from parvocellular cells
  4. Less dopamine in the portal means more prolactin is released due to less inhibition of the lacrotrophs
  5. Therefore prolactin concentration in blood increases, causing milk to be secreted from the mamillary glands
57
Q

Describe how milk is ejected from the nipple?

A
  1. Afferent pathways activated due to baby sucking on the nipple
  2. Oxytocin releasing neurone activity is increased
  3. More oxytocin released into blood stream
  4. Increased oxytocin increases milk ejection in mammary glands
58
Q

What is the name of the growth hormone?

A

Somatotrophin

59
Q

Is somatotrophin a peptide or steroid hormone?

A

peptide hormone

60
Q

What are the two ways that somatotrophin released from the pituitary works?

A

Directly to body tissues and indirectly on the liver

61
Q

How does GH indirectly affect growth

A

GH stimulates the production of Insulin Growth Factor 1 (IGF1) which has its own receptors in tissues and influences growth

62
Q

What is it called when you have too much growth hormone?

A

Acromegaly

63
Q

What condition arises when you have acromegaly before puberty ends?

A

Gigantism

64
Q

Why is there no more height growth due to acromegaly after puberty?

A

The growth plates have fused

65
Q

What are some symptoms of acromegaly?

A

Macroglossia - Larger tongue
Prominent nose
Sweatiness
Headache
Increased hand and feet size
Sleep apnoea
prominent features (forehead)
Carpal tunnel syndrome

66
Q

How to test for carpal tunnnel syndrome ?

A

tinel’s test -tapping median nerve
Phalens test - praying hands inverted

67
Q

Why might patients with acromegaly have tingling in their fingers?

A

Due to carpal tunnel syndrome

68
Q

How do you think you could treat a patient with acromegaly?

A

Medical treatment: Somatostatin Anaologues
Antagonist of growth Hormone receptors so GH cannot bind to receptor eg Pegvisomont

Radiotherapy - beam of radio frequency into pituitary - not normally first line of treatment as you can damage other aspect of the pituitary

Surgery to remove tumour, through the nose to remove tumour, if fails then second attempt at surgery through sphenoid bone

69
Q

What is carpal tunnel syndrome?

A

When there is pressure on the median nerve in the wrist, which causes paraesthesia

70
Q

What are two types of hypothalamic neurosecretory cells?

A

Hypothalamic parvocellular cells and hypothalamus magnocellular cells

71
Q

What is constitutive secretion?

A

Secretion when its released as soon as its made

72
Q

2 hypothalamic nuclei that magnocellular nuerones extend from?

A

Supraoptic (AVP) and Paraventricular (Oxytocin)

73
Q

2 Physiological actions that oxytocin does

A

Myometrial cell contraction in uterus (Labour)
Myoepithelial cells in breast (milk ejection)

ENDOCRINOLOGY (20 decks)

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