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Perioperative Care > Endocrine Physiology > Flashcards

Endocrine Physiology Flashcards

1
Q

List the 3 types of hormones

A
  1. Steroids
  2. Peptides
  3. Altered amino acids
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2
Q

List the 3 types of hormone receptor

A
  1. Cell surface
  2. Cytoplasmic
  3. Nuclear (thyroid hormone)
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3
Q

Where is the hypothalamus situated

A

In the forebrain in the floor of the third ventricle between thalamus above and pituitary below

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4
Q

What links the hypothalamus to the pituitary gland

A

Hypophyseal stalk

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5
Q

Embryological origin of the anterior pituitary

A

Outpouching of tissue from the oral cavity (ectoderm)

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6
Q

Embryological origin of the posterior pituitary

A

Derived from a downgrowth of neural tissue, continuous with the hypothalamus

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7
Q

How is anterior pituitary hormone secretion regulated

A

By hormones secreted along the hypophyseal tract from the hypothalamus

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8
Q

List the hormones secreted from the anterior pituitary gland (6)

A
  1. ACTH
  2. TSH
  3. FSH
  4. LH
  5. Prolactin
  6. Growth hormone
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9
Q

List the hormones secreted from the posterior pituitary gland (2)

A
  1. Oxytocin

2. ADH

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10
Q

What stimulates secretion of ACTH

A

Corticotropin-releasing hormone from the hypothalamus

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11
Q

Function of ACTH

A
  • Stimulates release of glucocorticoids from the adrenal cortex
  • Stimulates release of beta-endorphin and precursors of melanin-releasing hormone
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12
Q

What stimulates secretion of FSH and LH

A

Gonadotrophin-releasing hormone (GnRH)

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13
Q

What stimulates secretion of prolactin

A

Factors that decrease dopamine lead to the release of prolactin

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14
Q

What inhibits the release of growth hormone

A
  • Growth hormone-inhibiting hormone

- Somatostatin

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15
Q

Which cells produce oxytocin

A

Cells of the paraventricular nucleus of the hypothalamus

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16
Q

What stimulates the secretion of oxytocin

A

Sensory stimuli activating mechanoreceptors in the breast during suckling

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17
Q

Function of oxytocin

A
  • Milk ejection
  • Uterine contraction
  • Sexual arousal
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18
Q

Which cells produce ADH

A

Cells of the supraoptic nucleus of the hypothalamus

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19
Q

Why does amenorrhoea occur in hyperprolactinaemia

A

Inhibitory effect of high prolactin on GnRH production

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20
Q

Disorders caused by raised growth hormone

A
  • Children = gigantism

- Adults = acromegaly

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21
Q

Diagnostic criteria for SIADH

A
  • Hyponatraemia
  • Reduced plasma osmolality
  • Raised urine osmolality
  • Urinary Na >30
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22
Q

List the causes of SIADH

A
  1. Tumours - lung, pancreas, lymphomas
  2. TB
  3. Lung abscess
  4. CNS lesions e.g. meningitis
  5. Metabolic e.g. alcohol withdrawal
  6. Drugs e.g. Carbamazepine
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23
Q

What is Kallman Syndrome

A

LH and FSH deficiency

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24
Q

What is Sheehan’s Syndrome

A

Pituitary infarction following post-partum haemorrhage

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25
Q

Microscopic structure of the thyroid gland

A

Outer layer of cuboidal epithelium filled with colloid

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26
Q

Which cells secrete Calcitonin

A

Parafollicular C cells

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27
Q

What are Thionamides

A
  • Antithyroid drugs
  • e.g. Carbimazole, propythiouracil
  • Competitively inhibit the peroxidase-catalysed reaction (iodide to iodine)
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28
Q

What are anion inhibitors

A
  • Antithyroid drugs
  • e.g. Perchlorate
  • Competitively inhibit the uptake of iodine
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29
Q

Significant side effect associated with Perchlorate

A

Aplastic anaemia

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30
Q

Outline the process by which thyroid hormones are secreted

A
  1. Hypothalamus releases thyrotropin-releasing hormone
  2. Transported to endocrine cells of anterior pituitary which secrete TSH
  3. TSH stimulates thyroid hormone production and secretion
  4. T3 and T4 have a negative feedback effect on TRH
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31
Q

What is the majority of thyroid hormone in the circulation bound to

A

Thyroglobulin

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32
Q

In which phase of thyroiditis would a patient be found to be hyperthyroid and why

A
  • Acute phase

- Early phase of cell injury causes release of stored thyroid hormone

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33
Q

What drug is classically associated with hyperthyroidism

A

Amiodarone

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34
Q

What is Plummer’s disease

A

Hyperthyroidism secondary to solitary toxic adenoma/nodule

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35
Q

Which ovarian tumour is associated with secondary hyperthyroidism

A

Struma ovarii

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36
Q

Which drug is classically associated with hypothyroidism

A

Lithium

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37
Q

Biochemical presentation of sick euthyroid syndrome

A
  • Low T4/T3

- Low TSH

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38
Q

How does Calcium affect the permeability of the Na channel in nerve and muscle

A
  • Low Calcium = Increased permeability to Na causing increased depolarisation
  • High Calcium = Reduced permeability, decreasing nerve and muscle activity
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39
Q

Why is Calcium essential for clotting

A

Co-factor to several clotting factors

40
Q

What stimulates PTH release

A

Fall in extracellular fluid Calcium level

41
Q

List the ways in which PTH causes calcium to rise

A
  1. Stimulates release from bone
  2. Increases uptake from renal tubules
  3. Stimulates urinary phosphate excretion
  4. Increases rate of vitamin D activation in the kidney
42
Q

How is Calcium released from bone in response to TSH

A
  • Initially = rapid Calcium release from osteocytes mobilising the exchangeable bone calcium
  • Long-term = osteoclasts release Calcium from the bone pool
43
Q

What stimulates the conversion of Vitamin D into its active form

A
  1. PTH

2. Low phosphate levels

44
Q

How does Vitamin D increase plasma Calcium levels

A
  • Increases Calcium and phosphate absorption from the gut
  • Increases renal tubular absorption of calcium and phosphate
  • Stimulates osteoclastic bone resorption
  • Promotes mineralisation of osteoid
45
Q

How does Calcitonin reduce serum calcium levels

A
  • Reduces calcium and phosphate reabsorption from the renal tubules
  • Stimulates osteoblasts to mineralise bone
46
Q

What regulates phosphate levels

A
  • PTH reduces phosphate levels

- Vitamin D increases phosphate levels

47
Q

Most common cause of primary hyperparathyroidism

A

Single adenoma

48
Q

Describe secondary hyperparathyroidism

A
  • Conditions such as chronic renal failure cause prolonged hypocalcaemia
  • Causes parathyroid gland hypertrophy
  • Results in low/normal Calcium and raised PTH
49
Q

Difference between PTH and PTH-rp

A
  • PTH = 84 amino acid polypeptide

- PTH-rp = 141 amino acid polypeptide

50
Q

What is the result of vitamin D deficiency

A
  • Adults = osteomalacia
  • Children = rickets
    (Inadequate mineralisation of bone)
51
Q

List the causes of Vitamin D deficiency

A
  • Dietary e.g. vegans
  • Lack of sunlight
  • Malabsorption e.g. post-gastric surgery, Coeliacs
  • Renal disease
  • Hepatic failure
  • Vitamin-D resistant rickets
52
Q

Describe the symptoms of hypocalcaemia

A

Symptoms related to neuromuscular irritability:

  • Paraesthesia
  • Numbness
  • Cramps
  • Tetany
  • Chovtek’s sign
  • Trousseau’s sign
53
Q

ECG features of hypocalcaemia

A

Prolonged QT interval

54
Q

ECG features of hypercalcaemia

A

Reduced QT interval

55
Q

List the common causes of hypercalcaemia

A
  • Excess PTH
  • Excess Vitamin D
  • Sarcoidosis
  • Milk-Alkali syndrome
  • Drugs e.g. Thiazides
  • Malignancy
56
Q

Symptoms of hypophosphataemia

A
  • Confusion
  • Convulsions
  • Muscle weakness
  • Reduced 2,3-DPH causes left shift of oxygen dissociation curve
57
Q

List the causes of hypophosphataemia

A
  • Hyperparathyroidism (PTH reduces renal tubule absorption)
  • Vitamin D deficiency
  • TPN
  • DKA
  • Alcohol withdrawal
  • Acute liver failure
  • Paracetamol overdose (phosphaturia)
58
Q

How is the adrenal cortex divided and what does each division secrete

A
  1. Zona Glomerulosa = mineralocorticoids
  2. Zona Fasciculata = glucocorticoids
  3. Zona Reticularis = sex hormones
59
Q

What are Chromaffin cells

A

Specialised sympathetic post-ganglionic neurones situated in the adrenal medulla

60
Q

What stimulates the adrenal medulla to secrete catecholamines

A

Sympathetic stimulation via splanchnic nerves which secrete ACh

61
Q

What is produced by the adrenal medulla

A
  • Epinephrine (adrenaline)
  • Norepinephrine (noradrenaline)
  • Dopamine
  • Beta-hydroxylase
  • ATP
  • Opioid peptides
62
Q

What stimulates aldosterone secretion

A
  1. RAS system (specifically angiotensin 2)
  2. Hyperkalaemia
  3. ACTH
63
Q

List the actions of aldosterone

A
  1. Stimulates Na+ reabsorption from DCT
  2. Secretion of K+ in DCT
  3. Secretion of H+ in DCT
64
Q

List the glucocorticoids released from the Zona Fasciculata

A
  • Cortisol
  • Corticosterone
  • Cortisone
65
Q

What is the majority of cortisol bound to

A
  • Transcortin (75%)

- Albumin (15%)

66
Q

What stimulates the release of cortisol

A
  • ACTH
  • Circadian rhythm
  • Stress
  • Trauma
  • Burns
  • Infection
  • Exercise
  • Hypoglycaemia
67
Q

List the metabolic effects of cortisol

A

(Generally oppose those of insulin)

  • Breakdown of protein into amino acids
  • Gluconeogenesis
  • Storage of glucose as glycogen
  • Lipolysis
68
Q

What is the cardiovascular significance of cortisol

A

Required for vasopressors to work

69
Q

What stimulates the release of androgens from the zona reticularis

A

ACTH

70
Q

Which amino acid are epinephrine and norepinephrine synthesised from

A

Tyrosine

71
Q

Which receptors does norepinephrine mainly bind to

A

Alpha receptors (alpha-1)

72
Q

Which receptors does epinephrine mainly bind to

A

Beta receptors

73
Q

Which enzymes inactivate catecholamines

A
  • Monoamine oxidase

- Catechol-0-methyltransferase

74
Q

Mineralocorticoid deficiency features of Addison’s disease

A
  • Dehydration from increase Na+ loss
  • Hyponatraemia
  • Hypotension
  • K+ retention causing hyperkalaemia
  • H+ retention causing acidosis
75
Q

Glucocorticoid deficiency features of Addison’s disease

A
  • Weight loss
  • Anorexia
  • Lethargy
  • Hypoglycaemia during fasting
76
Q

What is the most common cause of primary hyperaldosteronism

A

Adrenal adenoma (Conn’s) - 60-70%

77
Q

Describe secondary hyperaldosteronism

A

Results from excess secretion of renin due to:

  • Renal artery stenosis
  • CCF
  • Cirrhosis
78
Q

Outline the effects of hyperaldosteronism

A
  • Sodium and water retention causing HTN
  • Renal K+ loss causing hypokalaemia
  • Renal H+ loss causing metabolic alkalosis
79
Q

What is Cushing’s disease

A

ACTH-secreting pituitary tumour

80
Q

What is the cause of Adrenogenital syndrome (Congenital adrenal hyperplasia)

A
  • Genetic deficiency in the enzymes involved in cortisol synthesis
  • Results in reduced cortisol but increased ACTH
  • Unused cortisol precursors are driven into the androgenic hormone synthetic pathway
81
Q

Phaeochromocytoma is a tumour of

A

Chromaffin cells of the adrenal medulla

82
Q

List the effects of increased circulating catecholamines

A
  • Palpitations and arrhythmias
  • Tremors
  • Sweating and flushing
  • Episodic HTN
  • Episodic hyperglycaemia
83
Q

When is the most growth hormone released in the day

A

During periods of deep sleep

84
Q

List the causes of GH stimulation

A
  • Hypoglycaemia
  • Anxiety
  • Pain
  • Hypothermia
  • Haemorrhage
  • Trauma
  • Fever
  • Exercise
85
Q

Role of growth hormone in the adult

A
  • Increased glycogenolysis
  • Reduced glucose uptake by cells
  • Promotes amino acid uptake into cells
  • Promotes protein synthesis
  • Increases lipolysis
  • Reduced LDL cholesterol
86
Q

Role of growth hormone in children/adolescents

A

Stimulates skeletal growth through stimulating mitosis in the cartilage cells of the epiphyseal plates

87
Q

List the hormones that increase with stress

A
  • GH
  • Cortisol
  • Renin
  • ACTH
  • Aldosterone
  • Prolactin
  • ADH
  • Glucagon
88
Q

List the hormones that decrease with stress

A
  • Insulin
  • Testosterone
  • Oestrogen
89
Q

List the hormone that are unaffected by stress

A
  • TSH
  • LH
  • FSH
90
Q

Sympathetic response following trauma

A
  • Sympathetic stimulation
  • Caused catecholamine release
  • Results in tachycardia/HTN
  • Blood is redistributed to heart/muscle/brain
91
Q

How is insulin release inhibited by stress

A

Beta-cells are inhibited by the alpha-2 adrenergic inhibitory effects of catecholamines

92
Q

Effect of trauma on glucose

A

Initial hyperglycaemia

93
Q

Effect of trauma on salt and water metabolism

A

ADH causes water retention, concentrated urine, and potassium loss which can continue for 3-5 days

94
Q

Which cytokine is mainly associated with surgery

A

IL-6 (peaks 12-24 hours following surgery

95
Q

How can spinal anaesthesia affect the response to surgery

A

Reduces changes in:

  • Glucose
  • ACTH
  • Cortisol
  • GH
  • Epinephrine

Perioperative Care (6 decks)

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