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medicine unit 10 uos > Endocrinology I > Flashcards

Endocrinology I Flashcards

1
Q

What are the functions of endocrine glands?

A

Regulate concentration of blood fluid (haemostasis)
Regulate body temperature
Regulation of reproduction, development and metabolism

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2
Q

What are the three major classes of hormones?

A

Polypeptide - proteins and peptides (water soluble)
Amine - derived from amino acids (water soluble)
Steroid hormones (lipid soluble)

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3
Q

What is the HPA pathway for stress and circadian rhythm?

A

Stressful stimulus causes the hypothalamus to release CRH
CRH stimulates the pituitary gland to release ACTH
ACTH stimulates the adrenal cortex which releases cortisol and androgens > stress metabolism. Positive and negative feedback

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4
Q

How is hormone secretion regulated?

A

Positive feedback and negative feedback loops
Positive feedback loop: hormones act on anterior pituitary
Negative feedback long loops: hormones act on anterior pituitary and hypothalamus. Short loops from anterior pituitary to hypothalamus

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5
Q

What is the embryological origin of the pituitary gland?

A

Anterior lobe (adenohypophysis) - protrusion of the ectoderm from roof of mouth
Posterior lobe (neurohypophysis) - neuroectoderm

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6
Q

What is the difference between the anterior and posterior pituitary gland?

A

Anterior pituitary: synthesise and stores hormones
Posterior hormones: only stores and releases them

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7
Q

What are examples of hormones released by anterior lobe of pituitary gland? what cells release them?

A

GH by somatotrophs
TSH by thyrotrophs
ACTH by corticotrophs
FSH and LH by gonadotrophs
Prolactin by lactotrophs

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8
Q

What hormones are released by the posterior pituitary gland? what cells release them?

A

ADH and oxytocinby cell bodies of hypothalamic neurons, secreted by nerve terminals

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9
Q

Where do the problems lie in primary, secondary and tertiary endocrine disorders?

A

Primary - Thyroid gland, parathyroid gland
Secondary - Anterior pituitary
Tertiary - Hypothalamus

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10
Q

What may cause hypersecretion?

A

Hormone secreting tumours
Hyperplasia
Autoimmune stimulation
Ectopically produced peptide hormone - ACTH, ADH

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11
Q

What may cause hyposecretion?

A

Autoimmune disease
Tumours
Infection
Haemorrhage

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12
Q

What regulates GH release from the anterior pituitary?

A

GNRH from hypothalamus has positive feedback, stimulates GH release
Somatostatin from hypothalamus has negative feedback, inhibits GH release

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13
Q

What are the two functions of GH? How does it exert these functions?

A

Growth of skeletal and soft tissue
Metabolic on carbohydrate, lipid and protein metabolism
- Indirect - through hormone - IGF1/somatomedins
- Direct - through GH receptors in target tissue

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14
Q

When may GH secretion increase/decrease?

A

Increase: sleep, stress, young age
Decrease: old age, obesity

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15
Q

What are the direct actions of GH?

A
  • Increased cartilage formation, bone growth
  • Increaesd protein synthesis, cell growth and proliferation
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16
Q

What are the indirect actions of GH?

A

Increased lipolysis
Increased blood sugar

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17
Q

What can GH deficiency cause in children?

A

Pituitary dwarfism:
- Impaired pituitary GH secretion
- Decreased rate of growth and short stature
- Normal brain development
- Decreased plasma GH and IGF1
Laron dwarfism:
- Defective GH receptors in target tissue and defective IGF1 production
- Decreased plasma IGF1 but elevated plasma GH

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18
Q

What can GH deficiency cause in adults?

A

If GH deficiency occurs after epiphyseal fusion of long bones, height unaffected
- Increased body fat
- Reduced muscle mass
- Fatigue
- Decreased physical fitness

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19
Q

What does excess GH in children cause - before epiphyseal plates have fused?

A

Gigantism
Rapid increase in growth and weight
Can be due to tumour in pituitary that hypersecretes GH
- Large hands and feet
- Coarse facial features, frontal bossing, prognathism
- Headaches
- Excessive sweating

20
Q

What can excess GH cause in adults - once epiphyseal plates have fused?

A

Acromegaly
Excessive skeletal, soft tissue and internal organ growth
Acral bony overgrowth ->
- Frontal bossing
- Increased hand and foot size
- Mandibular enlargement with prognathism
- Frontal bossing
- Headaches, sweating, increased BP, increased blood glucose

21
Q

How may acromegaly be treated?

A

Somatostatin analogues - lanreotide, octreotide, pasireotide

22
Q

What does prolactin do? 4

A
  • Breast development
  • Milk production
  • Suppresses sex drive in both sexes
  • Anovulation in ovary
23
Q

What releases prolactin, and what causes increase in levels?

A

Secreted by lactotrophs
Inhibited mainly by hypothalamic dopamine in male and female
Level very low in male and female
Increases inly during pregnancy and breast feeding

24
Q

What are prolactinomas?

A

Tumour in pituitary gland that causes excess secretion of prolactin

25
Q

What are the symptoms of prolactinomas in men? 4

A

Men:
- Low sperm count
- Erectile dysfunction
- Low testosterone
- Gynaecomastia

26
Q

What are the symptoms of prolactinomas in women? 3

A

Women:
- Loss of menstruation
- Anovulation
- Galactorrhoea

27
Q

What are the symptoms found in both men and women with prolactinomas? 5

A
  • Loss of libido
  • Headache
  • Infertility
  • Secondary hypogonadism
  • Osteoporosis
28
Q

What synthesises and releases oxytocin?

A

Synthesised by paraventricular nucleus in hypothalamus
Stored and released by posterior pituitary

29
Q

What is the action of oxytocin?

A
  • Stimulates Myoepithelial cells of the mammary gland -> milk ejection
  • Stimulates Myometrium -> expulsion of foetus and placenta
    Both positive feedback mechanism
30
Q

What synthesises and releases ADH?

A

Synthesised by supraoptic nuclei of the hypothalamus
Stored and released by posterior pituitary

31
Q

What are the actions of ADH?

A
  • Increases water permeability of principal cells in late DCT and CT in kidney
  • Acts via V1 receptors in vascular smooth muscles to cause contractions
32
Q

What stimulates ADH secretion?

A
  • Increased body fluid osmolality
  • Decreased blood volume
  • Decreased blood pressure
  • Angiotensin II
  • Pain/stress
  • Nausea and vomiting
33
Q

What inhibits ADH secretion?

A
  • Decreased body fluid osmolality
  • Increased blood volume
  • Increased blood pressure
  • Atrial natriuretic peptide
  • Ethanol
  • Diuretic
34
Q

What can decreased ADH cause?

A

Decreased ADH action > diabetes insipidus (DI)
- Neurogenic DI
- Nephrogenic DI

35
Q

What causes neurogenic (central) DI?

A

(Decreased ADH secretion)
- Hypothalamus, pituitary tumour

36
Q

What causes nephrogenic DI?

A

(Failure to respond to circulating ADH)
- Polycystic kidneys
- Chronic pyelorephritis
- Lithium in drugs
- Mutation in V2 receptor gene

37
Q

What are the symptoms of DI?

A
  • Polyuria
  • Nocturia
  • Polydipsia
  • Passage of large volumes of dilute urine
  • Marked dehydration
  • Anorexia and epigastric fullness
  • Hypernatremia
  • Fatigue
38
Q

What investigatory tests are used to diagnose DI?

A
  • Serum osmolality
  • Serum electrolyte level
  • Urine osmolarity
  • Water deprivation test followed by vasopressin test
39
Q

What are the treatments for the different types of DI?

A

Central: synthetic AVP analogue desmopressin (DDAVP)
Nephrogenic: adequate fluid intake; salt restriction

40
Q

What disorders can occur with increased ADH?

A
  • Small cell lung cancer
  • Severe brain trauma
  • Sepsis or infection of the brain (meningitis)
41
Q

What are the signs and symptoms of increased ADH?

A
  • Plasma ADH abnormally high
  • Physiologic ADH regulation not working
  • Highly concentrated (hypertonic) urine
  • Hyponatremia and osmolality
  • Normal or high BP
42
Q

What is the treatment for increased ADH?

A

Stop fluid and
Treatment of underlying cause

43
Q

Where are gonadotrophins released from and what is there function?

A

FSH and LH released from gonadotropic cells of anterior pituitary
FSH:
- stimulate production of gametes
LH:
- female: matures follicles, trigger ovulation, stimulate release of estrogen and progesterone
- male: stimulate production of testosterone
Sex hormones have key role in bone metabolism

44
Q

What is the release of GnRH like?
What is the HPG affected by?
What eventually happens to HPG axis over time in males vs females?

A

GnRH secretion is pulsatile
HPG axis affected by: stress, weight loss, excercise
In time:
Deregulation of HPG leads to menopause in females
HPA activity in males decreases over time

45
Q

What is hypopituitarism and panhypopituitarism?

A

Hypopituitarism: deficiency of one or more hormones of the pituitary gland
Panhypopituitarism: absent production of all anterior pituitary hormones

46
Q

What may cause hypopituitarism?

A

Congenital or acquired defects
Compression (tumour), gene mutation, tumours, ischaemia, iatrogenic or chronic inflammation

medicine unit 10 uos (26 decks)

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