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Life Maintenance > Pituitary gland physiology > Flashcards

Pituitary gland physiology Flashcards

1
Q

What are the main functions of the endocrine system?

A

integrate body functions via secretion of biologically active neuroendocrine peptides into body

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2
Q

What is a hormone?

A

substance released in one tissue
travels in blood stream (usually)
to have action in alternative tissue
(although autocrine effects also occur)

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3
Q

What are the 3 modes of action of hormones?

A

autocrine (acting on cell which released hormone)

paracrine (acts on cell adjacent to the secretory cell)

endocrine (hormone travels via bloodstream to act on cell type in distant location to secretory cell)

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4
Q

What are the main physical properties of hormones?

A

peptides (charged)
steroid (aliphatic)
amino acid derivatives (this is variable)

Hormones act at surface or nuclear receptors

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5
Q

What are the main features of the endocrine system?

A 
mesoderm origin
transmission of signals via body fluids (mostly blood)
generalised circulation 
chemical signals
effects can take minutes to days
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6
Q

What is the anatomical position of the pituitary?

A

Immediately inferior to the hypothalamus

Lies in the Sella Turcica

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7
Q

What are the main structures that make up the pituitary?

A 
2 lobes:
Anterior pituitary (in front)
Posterior pituitary (at back)
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8
Q

How is the anterior pituitary lobe derived?

A

invagination of Rathke’s pouch

= this is the roof of the embryonic oropharynx

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9
Q

What structure connects the 2 lobes of the pituitary? What are its embryonic origins?

A

pituitary stalk
also connects the broad gland to the brain
Originates from a notochordal projection

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10
Q

What is are alternative names for the 2 lobes of the pituitary?

A

anterior lobe: adenohypophysis

posterior lobe: neurohypophysis

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11
Q

What is the blood supply of the pituitary gland?

A

long and short pituitary arteries

hypophyseal portal circulation. Begins as a capillary plexus around the arc

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12
Q

How were pituitary cell types originally defined histologically?

A

acidic dyes: orange-G

basic dyes: aldehyde fuscin

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13
Q

What are the 5 main hormones produced in the anterior pituitary?

A 
ACTH: regulates adrenal cortex
TSH: thyroid hormone regulation
GH: growth regulation
LH/FSH: reproductive control 
PRL: breast milk production
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14
Q

Which cell type in the pituitary produces LH/FSH?

A

gonadotroph cells
basophyllic staining
central distribution in gland
pleomorphic granules

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15
Q

Which cell type in the pituitary produces prolactin?

A

lactotroph cells
acidophyllic staining
peripheral distribution in gland
ovoid dense granules

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16
Q

Which cell type in the pituitary produces GH?

A

somatotroph cells
acidophyllic or chromophobic staining
peripheral distribution in gland
spherical granules

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17
Q

Which cell type in the pituitary produces ACTH?

A

corticotroph cells
acidophyllic or basophyllic staining
central distribution
stellate granules

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18
Q

Which cell type in the pituitary produces TSH?

A

thyrotroph cells
basophyllic staining
central and Pas Intermedia distribution
Irregular granules

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19
Q

What are the main posterior pituitary hormones?

A

ADH: water regulation
Oxytocin: breast milk expression

20
Q

What hypothalamic mediators are released to stimulate hormone release from the pituitary?

A

gonadotrophin releasing hormone: releases FSH/LH

GH releasing hormone: releases GH

thyrotrophin releasing hormone: releases TSH

Corticotrophin releasing hormone: releases ACTH

21
Q

In endocrinology, where are primary, secondary and tertiary pathologies?

A

Primary: end organ
Secondary: pituitary
Tertiary: hypothalamus

22
Q

How do hormones and fluid travel between the hypothalamus and pituitary?

A

via portal circulation

23
Q

In general, what is the function of hypothalamic factor?

A

Released from hypothalamus (tertiary source)
Acts on pituitary (secondary source)
Stimulates release release of pituitary hormone
Which then acts on the end organ (primary source)

24
Q

What organs does the end organ hormone have a negative feedback loop on?

A

Secondary and Tertiary organs

e.g. pituitary and hypothalamus

25
Q

What is the outcome in a negative feedback loop?

A

stopping of that hormone release for eg.

usually mediated by elevated secretion and or levels of that hormone in the system

26
Q

What are the main clinical presentations of pituitary tumours?

A

Hormone hypersecretion

Space occupying lesion (headaches, visual loss, cavernous sinus invasion - this is lateral to the sella tunica)

Hormone hypo secretion/deficiency
(interference with remaining normal pituitary function)

27
Q

What are the names of the illnesses that are caused by pituitary hormone hypersecretion?

A 
GH: acromegaly
ACTH: Cushing's disease
TSH: Secondary thyrotoxicosis
LH/FSH: non-functioning pituitary tumour 
PRL: prolactinoma

These are often caused by pituitary tumours

28
Q

What is IGF-1?

A

Insulin-Like GF
Produced primarily by liver
Release is stimulated by GF
works in conjunction with GF to stimulate cell growth and proliferation

29
Q

What are some of the clinical systemic effects of GH/IGF excess?

A 
acromegaly
acanthosis nigricans 
fasting hyperglycaemia
insulin resistance + DM
(increased) nitrogen retention
high triglycerides
reduced total cholesterol 
increased skin thickness
30
Q

What are complications of excess GH/IGF?

A

Cardiomyopathy + hypertension
bowel polyps + colonic cancer
multimodal goitre + hypogonadism
arthropathy + obstructive sleep apnoea (OSA)

31
Q

What are the actions of cortisol?

A

increased plasma glucose levels:
increased gluconeogenesis, glycogenesis, glycogen storage
decreased glucose utilisation

increased lipolysis

Protein catabolism:
free aa are released

Na+ and H2O retention: maintains BP

Anti-inflammatory

Increased gastric acid production

32
Q

How does Cushing’s syndrome present clinically?

A

changes in sex hormones:
excess hair growth (e.g. hirtuism), irregular periods, infertility, impotence)

salt and water retention:
high BP, fluid retention

changes in protein and fat metabolism: 
central obesity
moon face
buffalo hump
think skin, easy bruising
osteoporosis 
DM
33
Q

What are the main features of prolactinomas?

A

fairly common
PRL is under different regulation to all other pituitary hormones
Dopamine inhibits PRL release
Positive feedback loop

34
Q

Which drugs interfere with dopamine and prolactin (PRL) release and signalling?

A

anti-emetics
anti-psychotics
HRT
oral contraceptives

35
Q

What are the clinical features of PRL excess caused by prolactinoma? What illness does this cause?

A

known as Hypogonadism

Causes:
infertility
oligomenorrhoea
amenorrhoea
galactorrhea 
reduced libido 
impotence
36
Q

What is the treatment for prolactinomas?

A

dopamine agonists
e.g. bromocriptine, cabergoline
NOT SURGERY

37
Q

What are non-functioning pituitary tumours?

A

30% of all pituitary tumours
Hormone excess does not occur with these tumours

Symptoms associated more with space-occupying nature of lesion:
headaches, visual loss, nerve palsies, interference with remaining pituitary function (compression) causing hormone deficiency

38
Q

What is the treatment for non-functioning tumours?

A

transsphenoidal surgery ± radiotherapy

no effective medical therapy

39
Q

What is the order of hormones that are lost (due to impaired pituitary function) when there is an expanding pituitary tumour? Why? (think of biological importance)

A 
earliest loss:
LH/FSH (sex)
GH (growth)
TSH (metabolism)
ACTH (survival)
PRL (stalk compression, brain survival) 
last to be lost
40
Q

What is the treatment for pituitary adenomas?

A

Surgery: transsphenoidal, or adrenalectomy if Nelson’s syndrome)

Radiotherapy: SLOW

Drugs: block hormone action, or stop hormone release

41
Q

What are the main causes of pituitary failure?

A

Tumour (benign/malignant)
Trauma
Infection
Inflammation (sarcoidosis, histiocytosis)
Apoplexy (bleeding within organs, akin to a stroke)
Iatrogenic

42
Q

What is sarcoidosis?

A

formation of granulomas
Granulomas are abnormal collections of inflammatory cells
Can affect multiple and any organs
but most commonly, lymph nodes, lungs, skin etc
Cause is not well understood. May be triggered by infection or auto-immune reaction

43
Q

What is histiocytosis?

A

Histiocyte = dendritic cell or macrophage
(antigen presenting cell)
Histiocytosis is an elevated or abnormal number/level of histiocytes
Treated by chemotherapy

44
Q

What are the main clinical features of hypopituitarism?

A

Thyroid: bradycardia, weight gain, cold intolerance, hypothermia, constipation

Reduced cortisol: tiredness, weakness, anorexia, postural hypotension, myalgia

Sex steroids: oligomenorrhoea, reduced libido, hot flushes, reduced body hair

Reduced GH: tired, central weight gain

45
Q

What are the treatment options for hypopituitarism?

A

Depends on which end organ (primary) tissues are affected. But is usually hormone replacement.

Thyroid: thyroxine

Sex steroids: testosterone, oestrogen

Reduced cortisol: hydrocortisone

Reduced GH: growth hormone

46
Q

What is secreted from the posterior pituitary?

A

ADH

Oxytocin

47
Q

Where are ADH and oxytocin made and how are they transported to the posterior pituitary?

A
  • made in hypothalamus

- transported by the hypothalamo-hypophyseal portal system

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