Pituitary Gland Flashcards

1
Q

What is a hormone?

A

A messenger

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2
Q

What are the two main groups of hormones?

A

Peptide

Steroid

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3
Q

How are peptide hormones synthesised?

A

As prohormones requiring further processing e.g. cleavage to activate

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4
Q

How are steroid hormones made?

A

In a series of reactions from cholesterol

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5
Q

How are peptide hormones stored?

A

In vesicles

Regulatory secretion

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6
Q

How are steroid hormones released?

A

Immediately

Constitutive secretion

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7
Q

Where are receptors for peptide hormones?

A

On cell membrane

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8
Q

Where are receptors for steroid hormones?

A

Intracellular

Change gene expression directly

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9
Q

What makes up the anterior pituitary?

A

Pars tuberalis
Pars intermedia
Pars distalis

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10
Q

Where does the pituitary gland sit?

A

In the sella turcica

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11
Q

What are parvocellular neurons?

A

Short neurons
Release hypothalamic factors into the capillary plexus in median eminence
Regulates anterior pituitary function

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12
Q

What are the 5 subtypes of endocrine cells that make up the anterior pituitary?

A
Somatotrophs
Lactotrophs
Corticotrophs
Thyrotrophs
Gonadotrophs
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13
Q

What is the first step of anterior pituitary regulation?

A

Axon terminals of hypothalamic neurosecretory cells release hormones into the hypothalamo-pituitary portal system

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14
Q

What is the second step of anterior pituitary regulation?

A

The RH’s and IH’s travel in the portal system to the anterior pituitary

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15
Q

What is the third step of anterior pituitary regulation?

A

The RHs and IHs stimulate or inhibit the release of hormones (black dots) from anterior pituitary cells

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16
Q

What is the fourth step of anterior pituitary regulation?

A

Anterior pituitary hormones leaves gland via the blood

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17
Q

What do the blood vessels make up?

A

Hypothalamo-pituitary portal system

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18
Q

What are somatotrophs?

A

Growth hormone

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19
Q

What do lactotrophs make?

A

Prolactin

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20
Q

What do thyrotrophs make?

A

Thyroid stimulating hormone

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21
Q

What do gonadotrophs makes?

A

Lutenising hormones

Follicle stimulating hormone

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22
Q

What do corticotrophs make?

A

Andrenocorticotrophic hormone

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23
Q

What is different about growth hormone?

What are the regulators?

A

Has on/off mode
On- growth hormone releasing hormone
Off- Stomatostatin

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24
Q

What is the regulator for prolactin?

A

Dopamine

Inhibitory

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25
Q

What is the hypothalamic stimulus for TSH?

A

Thyrotrophin releasing hormone

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26
Q

What is the hypothalmic receptors for LH and FSH?

A

Gonadotrophin releasing hormone

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27
Q

What is the regulator of ACTH?

A

Corticotrophin releasing hormone

28
Q

What are the main target cells for growth hormone?

A

Muscle fibres

Bones

29
Q

What are the main cell targets for prolactin?

A

Mammary glands

30
Q

Where are the main target cells for thyrotrophin?

A

Thyroid gland

31
Q

Where are the main target cells for gonadotrophins?

A

Ovaries and testes

32
Q

Where are the main target cells for corticotrophins?

A

Adrenal glands on top of kidneys

33
Q

What scan is used to look at the pituitary?

A

MRI

34
Q

What is the issue with pituitary tumours?

A

Compresses the optic chasm
Causes bilateral hemianopia
Loss of peripheral vision

35
Q

Why does compression of the optic chiasm cause bitemporal hemianopia?

A

Fibres from the nasal retinae cross and the optic chiasm
Compression of the optic chiasm by a pituitary tumour/suprasellar tumour prevents transmission of sensory information from lateral visual fields to the occipital Lobe

36
Q

What is the first step of milk production?

A

Mechanical stimulation of nipple and surrounding are activates afferent pathways

37
Q

What is the second step of milk production?

A

Afferent signals integrated in the hypothalamus and inhibit dopamine release from dopaminergic neurons

38
Q

What is the third step of milk production?

A

Less dopamine in the hypothalamic-pituitary portal system causes less inhibition of anterior pituitary lactotrophs

39
Q

What is the fourth step of milk production?

A

Increased plasma prolactin increases milk secretion in mammary glands

40
Q

What are the mechanisms of growth hormone action?

A

Directly bind to receptor on bones and muscles

Stimulates secretion of Insulin-like growth factor 1 and 2 from liver

41
Q

What conditions are caused by too much growth hormone?

A

Acrogemaly- Adults

Gigantism- Children

42
Q

What happens when you have too much growth hormone as a child?

A

Grow very tall

Growth plates haven’t fused yet

43
Q

What happens when you have too much growth hormone as an adult?

A
Coarsening of facial features
Macroglossia
Prominent nose
Large jaw - prognathism
Increased hand and feet size
Sweatiness
Headache
Numbness in your fingers due to compression of medial nerve (Carpel tunnel syndrome)
44
Q

What are the 2 posterior pituitary hormones?

A
Arginine vasopressin (ADH)
Oxytocin
45
Q

What are the main features of the posterior pituitary?

A

Posterior pituitary is anatomically continuous with hypothalamus

Hypothalamic magnocellular neurons:
Long, originate in supraoptic (AVP) and paraventricular (oxytocin) hypothalamic nuclei
Nuclei → stalk →posterior pituitary

46
Q

What is the first step of regulation of the posterior pituitary gland?

A

Two sets of hypothalamic neurosecretory cells produce AVP and oxytocin and transport them to the posterior pituitary

47
Q

What is the second step of regulation of the posterior pituitary?

A

Excitation of these hypothalamic magnocellular neurons stimulates release of AVP or oxytocin into the posterior pituitary where they diffuse into blood capillaries…

48
Q

What is the third step of regulation of the posterior pituitary?

A

Leave posterior pituitary via blood

49
Q

What are the main features of arginine vasopressin?

A

Other name = Anti-Diuretic Hormone
Diuresis = production of urine
Main physiological action = stimulation of water reabsorption in the renal collecting duct
This concentrates urine
Acts through the V2 receptor in the kidney

Also a vasoconstrictor (via V1 receptor)
Stimulates ACTH release from anterior pituitary

50
Q

What are the two main processes involving oxytocin?

A

Delivery of baby

Milk ejection

51
Q

What is the role of oxytocin in delivery?

A

Uterus at parturition

Causes contraction in myometrial cells

52
Q

What is the role of oxytocin in milk ejection?

A

Breast during lactation

Causes contraction of myoepithelial cells

53
Q

What is the first step in milk ejection?

A

Mechanical stimulation of nipple & surrounding area activates afferent pathways

54
Q

What is the second step in milk ejection?

A

Afferent signals integrated in the hypothalamus and stimulate oxytocin-releasing neuron activity

55
Q

What is the third step of milk ejection?

A

Action potentials travel down oxytocin neurons and oxytocin is secreted into the bloodstream

56
Q

What is the fourth step of milk ejection?

A

Increased plasma oxytocin increases milk ejection in mammary glands

57
Q

What is the anterior pituitary refferred to?

A

Adenohypophysis

58
Q

What is the posterior pituitary referred to?

A

Neurohypophysis

59
Q

What is the relationship between the hypothalamus and the pituitary?

A

Anterior- anatomically distinct

Posterior- direct continuation

60
Q

What do we call pituitary tumours?

A

Pituitary adenomas
Can be macro/micro
Macro if > 10mm

61
Q

What questions could you ask a patient who you might think acromegaly?

A

Have you noticed any enlargement of your hands or feet? Rings/ Shoes still fit?
Sweating more than normal?
Bumping into things- loss of peripheral vision?
Headaches?
Obstructive sleep apnea? Poor quality of sleep
Have you noticed any changed in your appearance?
Numbness in your fingers?

62
Q

What are the clinical features of acromegaly?

A
Sweating
Hypertension
Polyuria
Increased insulin resistance
Headaches
Coarse facial features
Enlargement of hands and feet
Macroglossia
63
Q

What is hypopituitarism?

A

Decrease in the production of other hormones

64
Q

Why do we not measure growth hormone in acromegaly?

A

Levels vary throughout the day

Borderline levels not distinctive between positive and negative results

65
Q

What hormones do we measure in tests for acromegaly?

A

Rather, we administer an agent that suppresses GH if it does not lower GH levels- acromegaly

66
Q

Which aquaporin is inserted into the serous membrane?

A

Aquaporin 3

67
Q

What is a normal response to increased vasopressin secretion?

A

Synthesis of aquaporin 2 in collecting duct cells