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1.5 Flashcards

1
Q

Which sinus lies anterior to the pituitary gland?

A

Sphenoid sinus

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2
Q

What lies superior to the pituitary?

A

Optic chiasm

  • A tumour/swelling of puit gland can lead to compression of optic chiasm (bitemporal, hemianopia)
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3
Q

Which pituitary lobe is directly connected to the hypothalamus?

A

Posterior lobe

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4
Q

Where does the pituitary gland sit?

A

In the sella turcica of sphenoid (hypophyseal fossa)

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5
Q

Which major hormones are secreted by the anterior lobe (adenohypophysis)?

A 
FSH/LH
PRL - prolactin
GH
TSH (thyroid)
ACTH (adrenal)
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6
Q

Which major hormones are secreted by the posterior lobe (neurohypophysis)?

A

Vasopressin (ADH)

Oxytocin

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7
Q

Roles of PRH and PIH?

A

PRH prompts the anterior pituitary to stimulate breast milk production through the production of prolactin. Conversely, PIH inhibits prolactin, and thereby, milk production.

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8
Q

What is GH released in response to?

A

GHRH (from hypothalamus)

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9
Q

What does somatostatin released from the hypothalamus inhibit?

A

Growth hormone from the anterior pituitary

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10
Q

Where does GH act?

A

Mostly acts via insulin-like growth factor-1 (IGF-1) on:

  • Soft tissue
  • Growth at physis of cartilaginous bones
  • Metabolic: lipolysis, gluconeogenesis, glycogenolysis
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11
Q

What is GH also called?

A

Somatotropin

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12
Q

How does thyrotropin releasing hormone (TRH - from hypothalamus) act on anterior pituitary gland?

A

Stimulates the release of thyrotropin (thyroid-stimulating hormone or TSH) and prolactin from the anterior pituitary.

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13
Q

How does dopamine affect prolactin release from ant. pituitary?

A

Inhibits it

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14
Q

Actions of prolactin in the body?

A

Breast tissue growth

Lactation

Inhibition of LH and FSH secretion (acts as a contraceptive for a few months after birth)

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15
Q

When is oxytocin released?

A

Suckling and labour (neural reflex)

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16
Q

Actions of oxytocin in the body?

A

Mammary duct myoepithelial cell contraction

Uterine myometrial contraction

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17
Q

What are pituitary adenomas?

A

Benign (mostly) tumours of the pituitary gland

They are often known to secrete hormones of pit gland depending on affected cells

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18
Q

Pituitary adenomas (benign tumours) can be caused by physical compression or excess secretion.

List the 3 common conditions caused by excess secretion of a particular hormone.

A

Prolactinoma (PRL secreting tumour)

Acromegaly (GH-secreting-tumour)

Cushing disease (ACTH secreting tumour) - hypercortisolemia

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19
Q

What is Sheehan’s syndrome?

A

Related to pregnancy and major haemorrhage following partiution.

Pituitary gland hypertrophied due to lactotrophs so it demands high oxygen.

When mum hypotensive post-partum –> pituitary insufficiency (pan-hypopituitarism)

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20
Q

An enlarged thyroid (goitre) gland can compress which 3 important structures?

A

Oesophagus - dysphasia
Recurrent laryngeal nerve - horse voice
Trachea - dyspnea, SoB

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21
Q

Which arteries supply the thyroid gland?

A

4 major arteries - 2 on each side

Superior thyroid arteries (branch of external carotid)

Inferior thyroid arteries (branch of thyrocervical trunk - branch of subclavian a.)

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22
Q

Which arteries drain the thyroid gland?

A

6 total - 3 on each side

Superior thyroid vein (L&R)
Middle thyroid vein (L&R)
Inferior thyroid vein (L&R)

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23
Q

What are follicles in the thyroid, surrounded with?

A

Follicular cells (involved in thyroxine synthesis)

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24
Q

What do the parafollicular cell (C-cells) of the thyroid synthesis and secrete?

A

Calcitonin

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25
Q

Describe stages of thyroid hormone synthesis

A

Iodine imported

Thyroglobulin synthesised

Iodination of tyrosine in follicle lumen using thyroid peroxidase

Thyroglobulin endocytosed back into follicular cell

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26
Q

Which hormone is mainly secreted by thyroid follicular cells?

A

T4

T4:T3 ration is 10:1

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27
Q

Where to thyroid hormones act?

A

Nuclear receptors (they diffuse across plasma membrane of target cells)

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28
Q

In hypothyroidism when problem not in anterior pituitary what is the TSH levels like?

A

High

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29
Q

In hyperthyroidism when problem not in ant. pituitary what are the TSH levels like?

A

Low - due to negative feedback

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30
Q

Most common cause of hypothyroidism in UK?

A

Hashimoto thyroiditis - seen more commonly in younger females

Autoimmune (anti-thyroid peroxidase)

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31
Q

Common cause of hypothyroidism in less developed countries?

A

Iodine deficiency - large goitres

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32
Q

Most common cause of hyperthyroidism?

A

Graves’ disease
- Stimulatory autoantibody (anti-TSH receptor antibodies)

Leads to hyper-metabolic effects

33
Q

What does growth hormone act via?

A

IGF-1

Excess causes acromegaly

34
Q

Lack of hypothalamic dopamine causes what?

A

Hyperprolactinaemia

35
Q

What hormone is made from cleavage of iodinated thyroglobulin (T4) wither peripheral deiodination?

A

Active T3

36
Q

How many parathyroid glands are there?

A

4

37
Q

Where do the parathyroid glands lie relative to the thyroid gland?

A

Posterior to thyroid gland - there can be variation and ppl can have up to 8 parathyroid glands

38
Q

Chief cells are found in the parathyroid gland. What do they synthesis?

A

PTH

39
Q

Name the cell types found in parathyroid gland

A 
Chief cells (synthesises PTH)
Oxyphil cells (unknown function)
Adipocytes
40
Q

Name the 2 functions of PTH

A

Increase calcium reabsorption in bowels

Vitamin D hydroxylation in kidney

41
Q

Effects of 1, 25 hydroxy-vitamin D

A

Increases calcium absorption from intestines

Increases calcium reabsorption

42
Q

What does increased PTH secretion cause in the blood?

A

Increases plasma calcium levels through bone resorption and increased absorption in kidneys and bowels.

43
Q

When plasma calcium levels are too high what hormone prevents further bone resorption?

A

Calcitonin

44
Q

Hypercalcaemia is a common electrolyte abnormality. What does it cause clinically?

A

Stones - renal stones
Bones - bone pain due to bone resorption
Abdominal moans
Psychic groans - hypercalcaemia linked to psychosis

45
Q

Causes of hypercalcaemia

A

Primary hyperparathyroidism

Drugs (e.g. thiazide diuretics)

Malignancy –>bone metastasis, PTHrP, myeloma, dehydration

Other

46
Q

How is hypercalcaemia treated?

A

IV fluids to dilute blood

Bisphosphonates - switch off osteoclasts and promote osteoblast activity

47
Q

Which cells are the cortex and medulla of adrenal glands derived from?

A

Cortex - mesoderm

Medulla - neural crest

48
Q

Are the adrenal glands retro- of ante- peritoneal?

A

Retro

49
Q

Name the 3 arteries that supply the left adrenal gland

A

Superior suprarenal artery (branch of inferior phrenic)

Middle suprarenal artery (branch of aorta)

Inferior suprarenal artery (branch of renal artery)

50
Q

How many veins drain the right adrenal gland?

A

1 the right suprarenal vein (drains directly to IVC)

51
Q

How many veins drain the L adrenal gland?

A

1 - L suprarenal vein

Drains into renal vein

52
Q

In adrenal microanatomy what does the zona glomerulosa release?

A

Mineralocorticoids (aldosterone)

53
Q

In the adrenal microanatomy what does the zona fasciculata release?

A

Glucocorticoids (cortisol)

54
Q

In the adrenal microanatomy what is the zona reticularis responsible for releasing?

A

Androgens - predominantly DHEA and androstenedione

55
Q

Name the zones of the adrenal cortex from the capsule (superficial) to adrenal medulla (deep)

A

Capsule

Zona glomerulosa - salt
Zona fasiculata - sugar
Zona reticularis - androgens

Medulla - chromaffin cells (secrete adrenaline mostly + NA)

56
Q

What is Conn’s syndrome?

A

Tumour of zona glomerulosa (most superficial layer of adrenal cortex)

Increases aldosterone secretion –> salt retained –> hypertension, hypernatraemia, hypokalaemia

Raise aldosterone to renin ratio

57
Q

Which food can mimic aldosterone?

A

Liquorice

58
Q

What does the adrenal medulla release?

A

80% adrenaline

20% noradrenaline

59
Q

Innervation of adrenal medulla

A

Sympathetic nervous system
- Preganglionic fibres from T5-T11 (release ACh)

Specialised sympathetic ganglion because normally postganglionic fibre synapse with effector organ/tissue but adrenal gland is special

60
Q

What is a pheochromocytoma?

A

Pheochromocytoma (PCC) is a neuroendocrine tumour of the medulla of the adrenal glands (originating in the chromaffin cells), or extra-adrenal chromaffin tissue that failed to involute after birth, that secretes high amounts of catecholamines, mostly NA, plus A to a lesser extent.

Treatment = blocking alpha and beta adrenoreceptors + surgical resection of tumour

61
Q

Which hormones are needed in the HPA axis?

A

Stress –> hypothalamus releases CRH –> anterior pituitary releases ACTH –> adrenal gland releases cortisol

62
Q

What is CRH?

A

Corticotrophin releasing hormone

Secreted by hypothalamus

Acts on anterior pituitary

63
Q

What is ACTH?

A

Adrenocorticotropic hormone

Secreted by anterior pituitary gland

Acts on adrenal gland

64
Q

What is Addison’s disease?

A

Adrenocortical failure most commonly due to autoimmune.

Increased ACTH production causes pigmentation.

Cortisol + aldosterone deficiency.

It is characterised by progressive anaemia, low blood pressure, great weakness, and bronze discolouration of the skin.

It is caused by inadequate secretion of hormones by the adrenal cortex.

65
Q

Why does Addison’s disease cause hyper-pigmentation?

A

Inadequate cortisol means there is less negative feedback on anterior pituitary so high levels of POMC (precursor of ACTH and alpha + beta melanocyte stimulating hormone).

Melanocyte stimulating hormone causes pigmentation. High levels causes hyper-pigmentation.

66
Q

What is Cushing syndrome?

A

Hyperadrenalism

Features of raised glucocorticoids

Most common cause = taking in exogenous steroids e.g. asthma treatment prednisolone

67
Q

What is Cushing disease?

A

Pituitary adenoma secreting ACTH

68
Q

In an adrenal tumour causing Cushing’s syndrome, what are the cortisol and ACTH levels like?

A

High cortisol

Low ACTH

69
Q

In Cushing’s disease, where by there is a pituitary tumour making ACTH. What are the cortisol and ACTH levels like?

A

ACTH normal or high

Cortisol high

70
Q

Cushing’s vs Addison’s based on cortisol levels.

A

Cushing’s syndrome/disease - cortisol levels are high

Addison’s disease - cortisol levels are low

71
Q

What do alpha cells (of pancreatic islets of Langerhans) secrete?

A

Glucagon - brings up blood glucose levels + inhibits insulin

72
Q

What do beta cells (of pancreatic islets of Langerhans) secrete?

A

Insulin - does the opposite of glucagon

73
Q

What do delta cells (of pancreatic islets of Langerhans) secrete?

A

Somatostatin - inhibits gastrin, CCK, VIP

74
Q

Actions of insulin

A

Increases glucose uptake by cells via GLUT-4 receptors

Glycogen synthesis

Reduced gluconeogenesis

Inhibition of lipolysis

Promotes de novo lipogenesis

75
Q

Why do you feel tired after a meal?

A

Reactive hypoglycaemia

Insulin released after a meal, this can cause plasma glucose levels to drop below normal levels –> hypo

76
Q

The incretin system (GLP-1) causes insulin release in response to what?

A

Oral glucose

77
Q

What disease does the following indicate?

Autoimmune, absolute insulin deficiency, ketones positive

A

Type 1 DM

78
Q

What is metformin?

A

A peripheral insulin sensitiser, wo/ hypoglycaemia

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