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Endocrinology > Lec3 - Nuts and Bolts of the Endocrine System > Flashcards

Lec3 - Nuts and Bolts of the Endocrine System Flashcards

1
Q

The endocrine system is a:

A

System of hormone secreting glands

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2
Q

The endocrine system is essential for:

A

Normal growth and development
Adaptation to internal and external environment
Contribute to the process of sexual reproduction

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3
Q

The nervous system and the endocrine system interact at the:

A

hypothalamus

e.g. in the regulation of temperature, circadian rhythms and hunger etc

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4
Q

Characteristics of the hormones affecting other cells’ metabolism

A

Number of molecules of hormone available
Number of receptors available
Affinity of hormone to receptor

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5
Q

Name the chemical classifications of some hormones

A

Steroid e.g. testosterone, oestrogen
Peptide/ protein e.g. oxytocin, ADH, insulin
(Amine e.g. adrenaline, noradrenaline and dopamine)
NO = nitric oxide is both a neurotransmitter and hormone

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6
Q

Name the sources of the hormone types

A

Steroid hormones: adrenal cortex, ovaries and testes (from embryonic mesodermal tissue)
Protein/peptide: adenohypophysis (from ectodermal tissue of the oral cavity)
Thyroid, parathyroid, pancreas (from the endodermal origin of GI tract)
Amine: thyroid, adrenal medulla (from ectodermal origin)

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7
Q

What is meant by diffuse neuroendocrine system?

A

Scattered nerve cells with endocrine function

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8
Q

Where is the pituitary gland located?

A

In the SELLA TURCICA of the sphenoid bone

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9
Q

What is the function of the pituitary gland?

A

It produces hormones which influence the activity of the other endocrine glands

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10
Q

What part of the pituitary gland is the adenohypophysis?

A

The anterior portion - the glandular part; outpouching of ectoderm of oral cavity - Ratke’s pouch

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11
Q

What part of the pituitary gland is the neurohypophysis?

A

The posterior portion - the neural part - down growth from the diencephalon of the brain

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12
Q

What is the blood supply to the pituitary gland?

A

Superior hypophyseal artery

Inferior hypophyseal artery

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13
Q

The superior and inferior hypophyseal arteries are branches of which artery?

A

Internal carotid

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14
Q

The superior hypophyseal artery supplies:

A

the median eminence &

upper part of the stalk/infundibulum

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15
Q

The inferior hypophyseal artery supplies:

A

the neurohypophysis &

lower part of the stalk/ infundibulum

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16
Q

The arteries that supply the median eminence and stalk/infundibulum end as what?

A

Capillary plexuses

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17
Q

The capillary plexuses in the median eminence and stalk ending are drained by:

A

portal veins

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18
Q

The portal veins then pass to:

A

The anterior lobe of the pituitary gland where they form a secondary plexus

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19
Q

What is the significance of the portal veins which run from the capillary plexuses in the median eminence and stalk ending to the anterior lobe of pituitary?

A

It provides a route for the neurosecretory substances released from the hypothalamus to also reach the anterior lobe

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20
Q

What controls hormone release from both adenohypophysis and neurohypophysis

A

Signals from the hypothalamus

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21
Q

What is the shape and location of the thyroid gland?

A

A bilobed gland in the neck (4x2 cms in size) weighing ~30g

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22
Q

What is the point of connection of the two lateral lobes called?

A

ISTHMUS - lies anterior to the trachea

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23
Q

What the upper and lower limits of the lobes of the thyroid gland?

A

From just below the oblique line of the thyroid cartilage to the 5/6th tracheal ring, immediately anterior to the trachea

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24
Q

What type of tissue is the thyroid gland derived from?

A

Endoderm

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25
Q

How does the thyroid gland develop?

A

It develops as a growth from the floor of the pharynx, near the base of the tongue

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26
Q

What is the role of the thyroid gland?

A

Essential role in regulating tissue metabolism, growth and development

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27
Q

What is secreted by the thyroid gland?

A

T3 - triiodothyronine

T4 - thyroxine

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28
Q

What is the arterial supply to the thyroid gland?

A

Superior thyroid artery from the external carotid

Inferior thyroid artery from the subclavian artery

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29
Q

What are the veins that drain the thyroid gland?

A

From an extensive plexus, the blood drains into the internal jugular and brachiocephalic veins

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30
Q

What type of surgery of the thyroid gland do you need to be careful with and why?

A

Cricothyrotomy - damage to the recurrent pharyngeal nerve from the vagus

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31
Q

How many parathyroid glands are there?

A

4 - 2 superior and 2 inferior

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32
Q

What is the location of the parathyroid glands?

A

Embedded in the capsule of the thyroid gland in the posterior aspect

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33
Q

How big are the parathyroid glands?

A

Very small - like a grain of rice and weight 40mg

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34
Q

How do the parathyroid glands develop?

A

Develop from endoderm tissue, mostly from cells originating from the 3rd/4th pharyngeal pouches and migrate caudally with the thymus

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35
Q

What is the role of the parathyroid glands?

A

To secrete parathyroid hormone

To regulate calcium and phosphate levels in homeostasis

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36
Q

Why must the parathyroid glands be preserved during thyroidectomy?

A

Because if removed, the blood calcium levels all and muscles including respiratory and laryngeal go into tetanic contraction leads to death

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37
Q

What is tetanic contraction and why does it occur?

A

Sodium and calcium compete for entry into cells
If calcium is removed, sodium is able to enter the cell freely, the cell becomes more positive, reaches threshold and action potentials are constantly fired. This causes constant contraction of muscle and they don’t relax

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38
Q

VAN of the parathyroid glands

A

Veins: superior, middle and inferior thyroid veins
Arteries: primarily inferior thyroid arteries (but also superior)
Nerves: from middle and inferior cervical ganglions

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39
Q

What is the location of the adrenal glands?

A

Superior pole of the kidneys - T12 and retroperitoneal

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40
Q

What are the shapes of the adrenal glands?

A

Right is pyramidal

Left is semilunar

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41
Q

What is the function of the adrenal glands?

A

Hormone release in response to stress

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42
Q

What is the origin of the adrenal glands?

A

Cortex derived from mesoderm

Medulla derived from neural crest cells

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43
Q

What is the function of the cortex?

A

To secrete corticosteroids
Cells adjacent to the capsule secrete MINERALOCORTICOIDS e.g. ALDOSTERONE - function to maintain electrolyte balance
Deeper part of cortex secretes GLUCOCORTICOIDS e.g. HYDROCORTISONE - affect metabolism and electrolyte balance
Inner part of cortex secretes ADRENAL ANDROGENS e.g. TESTOSTERONE

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44
Q

What are the secretory cells of the medulla?

A

Chromaffin cells

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45
Q

Where do chromaffin cells develop from?

A

The same embryonic tissue as the sympathetic ganglia

46
Q

What is the medulla regarded as?

A

Modified sympathetic ganglion (ANS)

47
Q

What does the medulla secrete?

A

Adrenaline and smaller amounts of noradrenaline (catecholamines)

48
Q

What effect does secretion of adrenaline and noradrenaline from the medulla have?

A

“Fight or flight” response - affects heart rate, metabolism, blood pressure and smooth muscle of viscera

49
Q

What is the arterial supply to the adrenal glands?

A

Superior suprarenal artery (from the inferior phrenic artery)
Middle suprarenal artery (from aorta)
Inferior suprarenal artery (from renal)

50
Q

What controls the thyroid gland?

A

The hypothalamus releasing Thyrotrophin releasing hormone (TRH)
Pituitary gland releasing Thyroid stimulating hormone (TSH)

51
Q

Describe the arterial supply to the cortex and medulla of the adrenal gland

A

The arteries branch before they enter the capsule, and the rami supply the cortex and medulla
Cortical arteries give rise to a SUBCAPSULAR PLEXUS and turn into CORTICAL SINUSOIDS that distribute blood to cortical cells

52
Q

How many sources of blood does the medulla receive?

A

Two

53
Q

What are the two sources of blood received by the medulla

A
  1. The rami from the branched arteries (superior, middle and inferior suprarenal arteries) supplying the cortex and medulla
  2. The medullary arteries which pass through the cortex to supply the medulla
54
Q

What is the significance of the two sources of blood to the medulla?

A

The hormones secreted by cortical cells can influence the activity of the cells in the medulla
e.g. cortisol mediates NA conversion to adrenaline

55
Q

What is the venous drainage of the adrenal glands?

A

Adrenal veins drain into the IVC (on the right)

or renal vein (on the left hand side)

56
Q

The activity of the adrenal glands is under the control of?

A

The hypothalamus & pituitary - ACTH

Sympathetic division of the ANS - coeliac plexus and splanchnic nerves

57
Q

How does the release of ACTH affect the adrenal glands?

A

ACTH stimulates secretion/release of corticosteroids

58
Q

Describe the ANS control of the medulla

A

The medulla is under direct control of the ANS - sympathetic division & therefore produces a very fast response
Preganglionic sympathetic fibres end in the chromaffin cells of the medulla
The chromaffin cells release catecholamines into adjacent circulation when they receive impulses from the preganglionic sympathetic fibres

59
Q 
Give the definitions of the following words:
Endocrine 
Autocrine 
Paracrine 
Neuroendocrine
A

Endocrine - the action of a hormone on a target organ far away from the secreting cell
Autocrine - the action of the hormone of the secreting cell itself
Paracrine - the action of the hormone on the adjacent cell
Neuroendocrine - neural stimulation of endocrine cells to secrete hormones e.g. medulla of the adrenal gland

60
Q

What are the clinical manifestations of endocrine diseases?

A 
Depends on whether it is:
A hormone overproduction
Hormone underproduction
OR
Tumour/mass/lesion which can be functional or non-functional
61
Q

What is the difference between a functional and non-functional tumour?

A

A functional tumour is associated with an overproduction of hormones
A non-functional tumour is associated with a pressure effect on surrounding tissues or structures

62
Q

What is the overall structure of an endocrine gland?

A

A functional unit consisting of cuboidal secretory cells with a lumen at the centre
Not all functional endocrine units have a lumen - pituitary and parathyroid gland cells have no lumen
Secretory cells supported by myoepithelial cells

63
Q

Describe three types of cells of the anterior pituitary gland

A

Acidophils - take up acidic dyes - stain pink
Basophils - take up basic dyes - stain purple
Chromophobe - no specific staining features

64
Q

Does the staining pattern relate to a specific hormone secretion?

A

No - ACTH is secreted by both basophils and chromophobes

65
Q

Name the types of pathology of the pituitary gland

A 
Pituitary adenoma (benign tumours)
- can be functional = secreting hormones causing HYPERPITUITARISM
or non-functional = not producing hormones - a pressure effect causing HYPOPITUITARISM
66
Q

What are the space occupying effects of functional or non-functional adenomas?

A 
Diplopia - double vision
Impaired vision because the skull cannot expand to allow for extra space being taken up 
Headaches
Nausea 
Vomiting
67
Q

What effect do cancers that metastasise to the brain have?

A

Space occupying - build up of pressure

68
Q

What are the names of the two hormones secreted by the thyroid gland?

A

Triiodothyronine T3

Thyroxine T4

69
Q

What is the function of T3 and T4?

A

To stimulate metabolic rate

70
Q

What is required in order to synthesise T3 and T4?

A

Iodine

71
Q

Where is iodine commonly found?

A

Sea salt

72
Q

What condition is associated with a lack of iodine?

A

GOITRE - an enlarged thyroid gland

73
Q

Why does the thyroid gland enlarge when there is a lack of iodine?

A

To absorb the maximum amount of iodine

74
Q

Describe the composition of a ‘normal’ thyroid gland

A

Thyroid tissue is composed of follicles with variable sized lumina
The follicles contain colloid with an eosinophilic/pink appearance
The follicles are lined with cuboidal cells

75
Q

The thyroid gland is highly vascular - True or False?

A

True

76
Q

What is the purpose of the fenestrations in the endothelial cells lining the capillaries around the thyroid gland?

A

The fenestrations allow passage of the hormone into the circulation

77
Q

What type of cells are found between the follicles?

A

Parafollicular cells or C cells

78
Q

What is the function of C cells?

A

C cells secrete calcitonin which promotes reduction of calcium concentration in the blood

79
Q

Describe the various types of pathology of the thyroid gland and their effects.

A

Goitre - enlargement of the thyroid gland - can be euthyroid
Grave’s Disease - excess T3 and T4 low TSH - causing hyperthyroidism
Hashimoto’s disease - low T3 and T4 high TSH - aka thyroiditis - causing hypothyroidism
Adenoma - can be euthyroid
Cancer - can be euthyroid

80
Q

Why does multi-nodular goitre occur?

A

Multi-nodular just means enlargement of many nodes
Due to a lack of iodine
Goitre due to hyperplasia and hypertrophy of the thyroid cells
The gland enlarges to maximise the amount of iodine absorbed

81
Q

How can patients with goitre be euthyroid?

A

Because the enlarged gland means more iodine is absorbed and so overcomes the deficiency - therefore the pt is euthyroid

82
Q

What gives rise to the irregular appearance of the thyroid gland in goitre?

A

Fibrosis of the thyroid tissue but the pt is euthyroid

83
Q

Why is it important to assess the radiology before thyroidectomy surgery?

A

The patient might arrest even after successful thyroidectomy due to tracheomalacia

84
Q

What is tracheomalacia?

A

softening of the trachea which collapses and obstructs the airways

85
Q

What do you do to prevent cardiac arrest during or after a thyroidectomy?

A

Intubate the patient

86
Q

What causes Grave’s disease?

A

Autoantibodies which stimulate TSH receptors

87
Q

What is Grave’s disease?

A

Diffuse enlargement of the thyroid gland - goitre due to hyperplasia of thyroid cells

88
Q

What characteristic appearance does a Grave’s disease thyroid gland have following thyroidectomy?

A

Vascular surface

89
Q

What characteristic appearance does the colloid have in Grave’s Disease and why?

A

The colloid has a ‘soap bubble’ appearance due to hyperactivity

90
Q

Name two associated consequences of Grave’s Disease

A

Infiltrative opthalmopathy - accumulation of soft tissue and inflammatory cells behind the eye leading to proptosis
Infiltrative dermopathy - thickening and induration of the skin on the anterior shin - pre-tibial myxoedema

91
Q

What is Hashimoto’s thyroiditis?

A

An autoimmune disease where the immune system destroys its own thyroid tissue
There is progressive depletion of thyroid cells by inflammation & replaced by fibrosis

92
Q

What happens to T3, T4 and TSH in Hashimoto’s thyroiditis?

A

Low T3/T4 and high TSH because the negative feedback is disrupted

93
Q

Name the four main types of thyroid carcinoma

A
  1. Papillary carcinoma (75-85%) increased risk of lymph node metastasis
  2. Follicular carcinoma (10-20%) increased metastasis to bone, lung and liver
  3. Medullary (5%) - arises from C cells; 20% as with MEN2 syndrome (multiple endocrine neoplasm)
  4. Anaplastic (<5%) - older patients & poor prognosis
94
Q

What is a follicular adenoma?

A

A benign tumour of the thyroid follicular cells - where the follicular cells join together

95
Q

What do parathyroid glands secrete?

A

Parathyroid hormone (PTH)

96
Q

What is the function of PTH?

A

To control levels of calcium in the blood - a decrease in blood calcium stimulates PTH secretion

97
Q

Describe the types of pathology of the parathyroid glands

A

Parathyroid adenoma - involving one gland
Parathyroid hyperplasia - involving all four glands
Both cause hypercalcaemia

98
Q

The adrenal glands consist of the adrenal cortex and medulla which are embryonically, morphologically and functionally distinct. True or false?

A

True

99
Q

What colour are normal adrenal glands and why?

A

Orange/yellow because the cells are rich in lipids

100
Q

Describe the different causes of adrenocortical hyperactivity

A

Adrenal hyperplasia, adenoma or cancer (rare)
Cushing’s syndrome
Conn’s syndrome
Adrenogenital syndrome

101
Q

What is Cushing’s syndrome?

A

Where there are excessive levels of cortisol

102
Q

What is Conn’s syndrome?

A

Excess levels of aldosterone

103
Q

What’s is adrenogenital syndrome?

A

Excess androgens

104
Q

Describe a cause of adrenocortical insufficiency

A

Addison’s disease

105
Q

What are the two types of adrenal cortex adenoma?

A

Functional adrenal cortex adenoma - can cause Cushing’s or Conn’s Syndrome
Non-functional adrenal cortex adenoma

106
Q

What is the function of the cells of the adrenal medulla?

A

To secrete catecholamines in response to intense emotional reaction - fight or flight hormones

107
Q

Secretion of catecholamines (noradrenaline, adrenaline, cortisol) results in:

A

vasoconstriction, increased heart rate, increased blood glucose - part of organism’s defence to stress

108
Q

Why do adrenal medulla cells stain darker than cortical cells?

A

Because medullary cells are neuroendocrine cells

109
Q

What is a phaeochromocytoma?

A

Adrenal medulla tumour

0.1 -0.3% cause of treatable hypertension

110
Q

Why are phaeos called 10% tumours?

A 
Because:
10% are familial as part of the MEN2 syndrome 
10% are extra adrenal 
10% are bilateral
10% are malignant 
10% arise in childhood
111
Q

What occurs as a result of a phaeo?

A

Due to high levels of catecholamines, there is a precipitous increase in BP, tachycardia, palpitations, headache, sweating, tremor and sense of apprehension

112
Q

What are complications of increased BP?

A

Congestive cardiac failure (CCF)
Ischaemic heart disease (IHD)
Cardiac arrhythmias
Cerebrovascular accident (CVA)

Endocrinology (11 decks)

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