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Endocrinology > The Pituitary Gland & It's disorders > Flashcards

The Pituitary Gland & It's disorders Flashcards

1
Q

Where is the pituitary located in relation to the brain?

A

Pituitary sits outside brain - meninges of brain is on top of pituitary

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2
Q

What important structures surround the pituitary gland?

A

Optic chiasm is above pituitary (vision)
Carotid arteries on either side of pituitary
Sphenoid bone below pituitary (sphenoid air sinus within bone)

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3
Q

Where is the hypothalamus located in relation to the pituitary?

A

Hypothalamus and cells controlling pituitary lie above pituitary
Portal blood vessels run along hypothalamic stalk

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4
Q

Describe the structure of the pituitary

A

Two lobes: Anterior and Posterior

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5
Q

Where in the body is the pituitary located?

A

Lies below brain in Sella Turcicia (depression in sphenoid bone)

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6
Q

Explain how the anterior lobe develops

A

Anterior Lobe derived from an invagination of the roof of embryonic Rathke’s Pouch (glandular cells)
Anterior hormones produced in pituitary

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7
Q

Why is the anterior lobe described as glandular?

A

The anterior pituitary produces and releases its hormones

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8
Q

Why is the posterior pituitary known as neurohypophysis?

A

The posterior pituitary stores and releases ADH and oxytocin which are produced in the hypothalamus

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9
Q

Describe how the link between the posterior pituitary and hypothalamus develops

A

A notochordal projection forms the pituitary stalk, which connects the gland to the brain and also the posterior lobe of the pituitary (neurohypophysis)

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10
Q

How does the posterior pituitary release its hormones?

A

Hormones produced outside pituitary and released onto posterior lobe
Release neurotransmitters directly into circulation as opposed to at a synaptic cleft

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11
Q

Describe the pituitary blood supply

A

Dual blood supply
Supply is via long and short pituitary arteries
Drainage is from hypophyseal portal circulation - this begins as a capillary plexus around the Arc (hypothalamus to pituitary)

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12
Q

What is meant by portal circulation?

A

Portal veins go from organ capillary bed → organ capillary bed

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13
Q

What are the functions of the two pituitary lobes?

A

Anterior: tropic hormones; controls endocrine system

Posterior; ADH and Oxytocin

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14
Q

Which hormones are released from the anterior lobe?

A

ACTH; adrenal cortex regulation

TSH; Thyroid hormone regulation

GH; growth (+)

LH / FSH; reproductive control

PRL; breast milk production

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15
Q

What hormones does the posterior lobe secrete?

A

Secretes nonapeptide hormones ADH + oxytocin

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16
Q

What are the effects of ADH?

A

water balance and regulation

vasoconstriction

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17
Q

What is the effect of oxytocin?

A

breast milk expression and uterine contractions

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18
Q

What are the 3 layers of the endocrine system?

A

Primary: end organ
Secondary: pituitary
Tertiary: hypothalamus

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19
Q

What is the significance of the primary endocrine layer (end organ)?

A

Primary layer - end organ hormone production
Sets endocrine status as either; hyper-, hypo- or eu (normal)
All tests start at end organ to see where pathology is

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20
Q

What is the role of the hypothalamus?

A

Hypothalamus takes electrical input from brain stem and higher centres to integrate them into chemical signals to release hormones

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21
Q

What is the significance of the pituitary in hormone release?

A

Hormones released into portal veins where they pass to pituitary so the signal can be amplified
~ 6 minutes to synthesise hormones

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22
Q

How is the process of hormone release sped up in the body?

A

There are peripheral and central hormones in system to speed up process

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23
Q

How do the peripheral and central hormones work in conjunction?

A

As soon as peripheral hormones released, they switch off central hormone production to prevent signals mixing
=> negative feedback

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24
Q

What are the clinical signs of a pituitary tumour?

A

Hormone hypersecretion
Space occupying Lesion
Hormone deficiency states

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25
What symptoms does a space occupying lesion cause?
Headaches Visual loss (field defect) Cavernous sinus invasion
26
What is the consequence of hormone deficiency?
Interference with surrounding normal pituitary
27
What can cause excess hormone ?
Tumours of the Anterior Pituitary can cause syndromes of hormone excess
28
What are the effects of excess anterior hormones?
GH (IGF-1) - acromegaly ACTH - Cushing's disease TSH - Secondary thyrotoxicosis LH / FSH - non-functioning pituitary tumour PRL - prolactinoma
29
What are the effects of growth hormone?
GH acts on liver to produce IGF-1 which acts on long bones to enables chondrocytes to grow and lay down more cartilage which osteophyte to cause bone growth
30
As well as GH, what other factors are required for growth?
Need to have sufficient energy and nutrients for growth
31
What are the metabolic effects fo growth hormone?
↑lipolysis and FFA ↑protein synthesis and a.a. uptake ↑gluconeogenesis in liver
32
What are the systemic effects of acromegaly?
``` Acral enlargement Macroglossia; can cause disruptive sleep apnoea Carpal tunnel syndrome Increased skin thickness + sweating Change appearance - Interdental spacing ; overgrowth of jaw Visceral enlargement Metabolic changes Diabetes mellitus Insulin resistance Reduced total cholesterol Increased TGs ```
33
What are the dangerous clinical consequences of acromegaly?
Cardiomyopathy Hypertension Bowel polyps Colonic cancer Multinodular goiter Hypogonadism Arthropathy OSA
34
What are the effects of cortisol on plasma [glucose]?
↑gluconeogenesis ↓glucose utilisation ↑glycogenolysis ↑glycogen storage - increases plasma glucose
35
What are the systemic metabolic effects of cortisol?
``` Increases lipolysis → Provides energy Proteins are catabolised → releases amino acids Na+ and H₂O retention maintains BP Anti-inflammatory Increased Gastric Acid production ```
36
What are the symptoms of Cushing's syndrome caused by disruption of fat and protein metabolism?
``` Changes in body shapes Central obesity Moon face Buffalo hump Thin skin, easy bruising Osteoporosis (brittle bones) Diabetes ```
37
What are the symptoms of sex hormone imbalance due to Cushing's?
Excess hair growth Irregular periods Problems conceiving Impotence
38
How does cushing's sydrome effect Na and water balance?
High blood pressure | Fluid retention
39
How does PRL control differ to other anterior hormones?
Stimulated externally (baby on nipple)
40
How is PRL release regulated?
Tonic release of DA inhibits PRL release | +ve feedback
41
How is PRL secretion achieved?
Afferent limb - neuronal signal from nipple to hypothalamus to switch off dopamine production - surge in PRL production Take baby off breast switches off PRL production as afferent limb no longer stimulated
42
What drugs interfere with DA and PRL secretion?
Antiemetics Antipsychotics OCP/HRT
43
What does excess PRL (hypogonadism) cause?
``` Infertility Amenorrhoea Reduced libido Oligomenorrhea Galactorrhoea Impotence ```
44
How is hypogonadism treated?
dopamine agonists:- - Bromocriptine - Cabergoline
45
What are non-functioning pituitary tumours?
No syndrome of hormone excess produced | - 30% of all pituitary tumours
46
How do non-functioning pituitary tumours cause symptoms?
Cause symptoms due to space occupation - Headache - Visual field defects - Nerve palsies - Interfere w/ pituitary function; hormone deficiencies
47
How do we treat non-functioning pituitary tumours?
surgery (transsphenoidal approach) ± radiotherapy | - No effective medical therapy
48
How do pituitary tumours impair vision?
Tumours can expand and damage optical chiasm
49
What is the optic chiasm?
crossing point of nasal and temporal retina
50
Explain how retinal neuron fibres allow us to see
Nasal retina and temporal retina on opposite side look at same place of object All neurones from nasal retina cross and line up with temporal neurones on other side - those two neurones looking at same piece of object go back to one piece of brain for interpretation
51
What is bitemporal hemianopia?
``` Bitemporal hemianopia (lost temporal visual field as nasal fibres damaged) Starts as bitemporal upper quadrantanopia as damages bottom cells of optic chiasm first (impairing top of visual field) ```
52
Outline the decrease in pituitary function as tumours expand
Function decreases in following order: 1. LH /FSH - sex 2. GH - growth 3. TSH - metabolism 4. ACTH - survival 5. ↑ PRL - stalk compression
53
Why does PRL increase with expanding tumours?
PRL increases as dopamine levels decrease
54
How are pituitary adenomas treated?
Surgery - Transsphenoidal - (Adrenalectomy - Nelson’s Syndrome) Radiotherapy - Slow Drugs - Block hormone production - Stop hormone release
55
What causes pituitary failure?
``` Tumour (most common) - Benign or malignant Trauma Infection (e.g. TB; disrupts meninges) Inflammation - Sarcoidosis - Histiocytosis Iatrogenic ```
56
What does hypothyroidism cause and how is it treated?
Bradycardia, weight gain, cold tolerance, hypothermia, constipation Treatment: thyroxine
57
What are the symptoms and treatments of reduced cortisol?
Tiredness, weakness, anorexia, postural hypotension, myalgia Treatment: hydrocortisone
58
What is the effect of decrease sex streoids production?
Oligomennorrhoea, Reduced libido, hot flushes, reduced body hair Treatment: testosterone, oestrogen
59
What are the consequences of decreased growth hormone and how is it treated?
Tired, central weight gain Treatment: growth hormone
60
What is the release of Vasopressin stimulated by?
Increased plasma osmolality Decreased BP (baroreceptors ↑PaCO₂ ↓PaO₂: shock Cortisol, sex steroids, angiotensin II
61
What are the effects of ADH/ vasopressin?
Collecting ducts ↑ H₂O permeability Reabsorption of free water Vasoconstriction
62
What is the cause of diabetes insipidus?
Underproduction of ADH
63
What are the 2 types of Diabetes Insipidus?
Cranial - lack of production Nephrogenic - Receptor in kidney resistance
64
What is SIADH?
Syndrome of Inappropriate ADH (SIADH) | Too much ADH
65
What are the causes of SIADH?
``` Brain injury / infection Lung cancer / infection asthma IPPV Metabolic - Hypothyroidism - Addison’s ```
66
How can we clinically detect SIADH?
↓Plasma Na+ (<130 mmol/L) ↓Plasma Osmolality (<270 mOsm/Kg) ↑Urine osmolality (>100 mOsm/Kg) ↑Urine sodium (>50 mmol/L)
67
How do we treat SIADH?
fluid restriction
68
How is diabetes insipidus diagnosed?
Polyuria (>3L) Polydipsia - ↑Na+, ↑plasma osmolality - ↓Urine osmolality, ↓Urine Na+

Endocrinology (12 decks)

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