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MCRP: Clinical Sciences > Endocrine Physiology > Flashcards

Endocrine Physiology Flashcards

1
Q

What does the adrenal medulla secrete?

A

Adrenaline
Small amount of noradrenaline

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2
Q

Where is ADH secreted and what is its function?

A

Released from Posterior pituitary

Promotes water reabsorption in the collecting ducts of the kidneys by the insertion of aquaporin-2 channels.

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3
Q

Where is ADH synthesised?

A

Supraoptic nuclei of the hypothalamus, released by the posterior pituitary

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4
Q

What factors cause increased secretion of ADH?

A
  1. Extracellular fluid osmolality increase
  2. Volume decrease
  3. Pressure decrease
  4. Angiotensin II
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5
Q

What factors cause decreased secretion of ADH?

A
  1. Extracellular fluid osmolality decrease
  2. volume increase
  3. temperature decrease
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6
Q

What are the two forms of diabetes insipidus?

A

Cranial diabetes insipidus
Nephrogenic diabetes insipidus

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7
Q

What is the pathophysiology of diabetes insipidius?

A

Characterised by either a deficiency of antidiuretic hormone, ADH, (cranial DI) or an insensitivity to antidiuretic hormone (nephrogenic DI)

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8
Q

How can cranial diabetes insipidius be treated?

A

Desmopressin
An analog of ADH

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9
Q

Where in the kidney of ADH work?

A

Collecting duct

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10
Q

What are the downstream metabolites of arachidonic acid metabolism?

A

Endoperioxidases:
Prostacyclin - decrease platelet aggregation
Thromboxane - increase platelets aggregation
Prostaglandin PGE2 - increases pain, temperature

Leukotrines:
- LTB4: Increased neutrophil chemotaxis
- LTA, LTC, LTD, LTE - bronchoconstriciton

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11
Q

What are leukotrienes?

A

A family of inflammatory mediators produced by leukocytes

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12
Q

What is the function of the leukotrienes LT A-E 4?

A

LTA4 - bronchoconstriction
LTB4 - Neutrophil chemotaxis
LTC4- bronchoconstriction
LTD4 - bronchoconstriction
LTE4 -bronchoconstriction

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13
Q

What antibiotics can you use when breast feeding?

A

Penicillins, cephalosporins, trimethoprim

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14
Q

What epilepsy medication can be used when breast feeding?

A

Sodium valproate
Carbamazepine

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15
Q

What anticoagulants can be used in breastfeeding?

A

Heparin
Warfarin

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16
Q

What drugs should be avoided in breast feeding?

A

Antibiotics: ciprofloxacin, tetracycline, Chloramphenicol, sulphonamides
Psychiatric drugs: lithium, Benzodiazepines
Aspirin
Carbimazole
Methotrexate
Sulfonylureas
Cytotoxic drugs
Amiodarone

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17
Q

What hormone co-ordinate calcium metabolism?

A

Main:
Parathyroid hormone (PTH)
1,25-dihydroxycholecalciferol (calcitriol, the active form of vitamin D)

Others:
Calcitonin
Thyroxine
Growth Hormone

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18
Q

What are the actions of PTH?

A

Increases plasma calcium, decreases plasma phosphate
Increases renal tubular reabsorption of calcium
Increases osteoclastic activity*
Increases renal conversion of 25-hydroxycholecalciferol to 1,25-dihydroxycholecalciferol
decreases renal phosphate reabsorption

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19
Q

What are the actions of 1,25-dihydroxycholecalciferol?

A

increases plasma calcium and plasma phosphate
increases renal tubular reabsorption and gut absorption of calcium
increases osteoclastic activity
increases renal phosphate reabsorption

Absorption from gut is > than kidneys

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20
Q

What is the action of calcitonin?

A

Secreted by C cells of thyroid
Inhibits osteoclast activity
Inhibits renal tubular absorption of calcium

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21
Q

What makes growth hormone?

A

secreted by the somatotroph cells of the anterior lobe of the pituitary gland.

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22
Q

What is the mechanism of action of growth hormone?

A

Acts on a transmembrane receptor for growth factor
binding of GH to the receptor leads to receptor dimerization
Acts directly on tissues and also indirectly via insulin-like growth factor 1 (IGF-1), primarily secreted by the liver

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23
Q

What increases secretion of growth hormone?

A

Growth hormone releasing hormone (GHRH): released in pulses by the hypothalamus
Fasting
Exercise
Sleep (particularly delta sleep)

24
Q

What decreases secretion of growth hormone?

A

Glucose
Somatostatin (itself increased by somatomedins, circulating insulin-like growth factors, IGF-1 and IGF-2)

25
Q

What are the causes of metabolic alkalosis?

A

vomiting / aspiration
vomiting may also lead to hypokalaemia
diuretics
liquorice, carbenoxolone
hypokalaemia
primary hyperaldosteronism
Cushing’s syndrome
Bartter’s syndrome

26
Q

What is the mechanism of metabolic alkalosis?

A

activation of renin-angiotensin II-aldosterone (RAA) system is a key factor
aldosterone causes reabsorption of Na+ in exchange for H+ in the distal convoluted tubule
ECF depletion (vomiting, diuretics) → Na+ and Cl- loss → activation of RAA system → raised aldosterone levels
in hypokalaemia, K+ shift from cells → ECF, alkalosis is caused by shift of H+ into cells to maintain neutrality

27
Q

What are features of primary hyperparathyroidism?

A

PTH (Elevated)
Ca2+ (Elevated)
Phosphate (Low)
Urine calcium : creatinine clearance ratio > 0.01

May be asymptomatic if mild
Recurrent abdominal pain (pancreatitis, renal colic)
Changes to emotional or cognitive state

Most cases due to solitary adenoma (80%),

28
Q

What are features of secondary hyperparathyroidism?

A

PTH (Elevated)
Ca2+ (Low or normal)
Phosphate (Elevated)
Vitamin D levels (Low

May have few symptoms
Eventually may develop bone disease, osteitis fibrosa cystica and soft tissue calcifications

Parathyroid gland hyperplasia occurs as a result of low calcium, almost always in a setting of chronic renal failure

29
Q

What are features of tertiary hyperparathyroidism?

A

Ca2+ (Normal or high)
PTH (Elevated)
Phosphate levels (Decreased or Normal)
Vitamin D (Normal or decreased)
Alkaline phosphatase (Elevated)

Occurs as a result of ongoing hyperplasia of the parathyroid glands after correction of underlying renal disorder, hyperplasia of all 4 glands is usually the cause

30
Q

What secretes prolactin?

A

Anterior pituitary

31
Q

What increases prolactin secretion?

A

thyrotropin releasing hormone
pregnancy
oestrogen
breastfeeding
sleep
stress
drugs e.g. metoclopramide, antipsychotics

32
Q

What decreases prolactin secretion?

A

Decreases secretion
dopamine
dopaminergic agonists

33
Q

What is the function of prolactin?

A

Stimulates breast development (both initially and further hyperplasia during pregnancy)
Stimulates milk production

It decreases GnRH pulsatility at the hypothalamic level and to a lesser extent, blocks the action of LH on the ovary or testis.

34
Q

What secretes renin?

A

Renin is secreted by juxtaglomerular cells and hydrolyses angiotensinogen to produce angiotensin I

35
Q

What factors cause secretion of renin?

A

hypotension causing reduced renal perfusion
hyponatraemia
sympathetic nerve stimulation
catecholamines
erect posture

36
Q

What factors reduce secretion of renin?

A

Factors reducing renin secretion
drugs: beta-blockers, NSAIDs

37
Q

What are the layers and secretions of the adrenal medulla?

A

Adrenal cortex (mnemonic GFR - ACD)

  • zona glomerulosa (on outside): mineralocorticoids, mainly aldosterone
  • zona fasciculata (middle): glucocorticoids, mainly cortisol
  • zona reticularis (on inside): androgens, mainly dehydroepiandrosterone (DHEA)
38
Q

What is the mechanism of angiotensin II?

A

angiotensin-converting enzyme (ACE) in the lungs converts angiotensin I → angiotensin II

39
Q

What is the action of angiotensin II?

A

causes vasoconstriction of vascular smooth muscle leading to raised blood pressure and vasoconstriction of efferent arteriole of the glomerulus → increased filtration fraction (FF) to preserve GFR. Remember that FF = GFR / renal plasma flow
stimulates thirst (via the hypothalamus)
stimulates aldosterone and ADH release
increases proximal tubule Na+/H+ activity

40
Q

What is the action of aldosterone?

A

released by the zona glomerulosa in response to raised angiotensin II, potassium, and ACTH levels
causes retention of Na+ in exchange for K+/H+ in distal tubule

41
Q

What isthe chloride shift?

A

Chloride shift
CO2 diffuses into RBCs
CO2 + H20 —- carbonic anhydrase -→ HCO3- + H+
H+ combines with Hb
HCO3- diffuses out of cell,- Cl- replaces it

Allows HCO3 to move into systemic circulation

42
Q

What is the Bohr effect?

A

Bohr effect
increasing acidity (or pCO2) means O2 binds less well to Hb

43
Q

What is the haldane effect?

A

Haldane effect
increase pO2 means CO2 binds less well to Hb

44
Q

What is the function of thiamine?

A

important in the catabolism of sugars and aminoacids. The clinical consequences of thiamine deficiency are therefore seen first in highly aerobic tissues such as the brain (Wenicke-Korsakoff syndrome) and the heart (wet beriberi).

45
Q

Conditions associated with low thiamine?

A

Wernicke’s encephalopathy: nystagmus, ophthalmoplegia and ataxia

Korsakoff’s syndrome: amnesia, confabulation

dry beriberi: peripheral neuropathy

wet beriberi: dilated cardiomyopathy

46
Q

Consequences of B2 deficiency?

A

Riboflavin
Consequences of riboflavin deficiency:
angular cheilitis

47
Q

What is vitamin B3 used for?

A

Niacin
precursor to NAD+ and NADP+ and hence plays an essential metabolic role in cells.

48
Q

Consequences of B3 deficiency?

A

Biiosynthesis of niacin issues:
Hartnup’s disease: hereditary disorder which reduces absorption of tryptophan

carcinoid syndrome: increased tryptophan metabolism to serotonin

Consequences of niacin deficiency:
pellagra: dermatitis, diarrhoea, dementia

49
Q

What is the use of vitamin B6?

A

Pyridoxine
converted to pyridoxal phosphate (PLP) which is a cofactor for many reactions including transamination, deamination and decarboxylation.

50
Q

Causes of vitamin B6 deficiency?

A

Causes of vitamin B6 deficiency
isoniazid therapy

51
Q

Features of B6 deficiency?

A

Consequences of vitamin B6 deficiency
peripheral neuropathy
sideroblastic anemia

52
Q

What clotting factors does vitamin K affect?

A

II, VII, IX, X

53
Q

How long does it take vitamin K to have an effect on clotting?

A

4 hours

54
Q

What is the function of vitamin C?

A

antioxidant
synthesis of collagen
facilitates iron absorption
cofactor for norepinephrine synthesis

55
Q

Features of vitamin C deficiency ?

A

gingivitis, loose teeth
poor wound healing
bleeding from gums, haematuria, epistaxis
general malaise

56
Q

What vitamin aids absorption of iron and why?

A

Vitamin C (ascorbic acid) supplementation can aid iron absorption from the gut by conversion of Fe3+ to Fe2+

MCRP: Clinical Sciences (11 decks)

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