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Metabolism, Endocrinology, Haematology > Endocrinology Session 3 > Flashcards

Endocrinology Session 3 Flashcards

1
Q

What is the function of the pituitary gland and the hypothalamus?*

A

Link between endocrine and nervous system

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2
Q

Where does the pituitary gland sit?

A

Sella turcica

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3
Q

What processes are modulated by the complex?

A
  • Growth
  • Reproduction
  • Adrenal gland function
  • Water homeostasis
  • Milk secretion and lactation
  • Thyroid gland function
  • Puberty
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4
Q

Why is the posterior pituitary not a true gland?

A

It secretes hormones that are produced by the hypothalamus

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5
Q

Where does the anterior pituitary gland arise from?

A
  • Oral ectoderm (Rathke’s pouch)

- Primitive gut tissue

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6
Q

What does the posterior pituitary gland arise from?

A

Neuroectoderm (primitive brain tissue)

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7
Q

How is the posterior pituitary gland physically connected to the hypothalamus?*

A

Through infundibulum

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8
Q

What nuclei secrete oxytocin and antidiuretic hormone in the posterior pituitary?

A

Supraoptic and paraventricular hypothalamic nuclei

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9
Q

How does the neurocrine function of the posterior pituitary occur?

A
  • Hormones from nuclei transported down axons to posterior pituitary
  • Stored and released from PP into general circulation to act on distant targets
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10
Q

Where are the hormones synthesised in hypothalamus stored?

A
  • Stored in median eminence
  • Released into blood supply called the HYPOPHYSEAL PORTAL SYSTEM (connection of two capillary beds) and into anterior pituitary
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11
Q

What is the function of the hormones released by the anterior pituitary?*

A

Stimulation/inhibition of target endocrine cells in anterior pituitary gland

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12
Q

What are the functions of anterior pituitary hormones?

A
  • Acting on neighbouring cells (autocrine/paracrine)

- Acting on distant targets (neurocrine)

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13
Q

What are the functions of the hormones secreted into the hypophyseal portal system?

A

Acting on endocrine cells within anterior pituitary

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14
Q

What is the function of ADH/vasopressin?

A

Regulation of body water volume and how much water is reabsorbed back into the body via the kidney

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15
Q

What is the function of oxytocin?

A
  • Regulating uterine contractions during childbirth

- Milk letdown during breastfeeding

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16
Q

What are the tropic (hormones that are affecting the synthesis and release of another hormone) hormones in the hypothalamus?

A

TRH (thyrotropin releasing hormone) - stimulate thyroid gland
PIH (prolactin release-inhibiting hormone) - dopamine
CRH (corticotropin release hormone) - ACTH and cortisol synthesis
GnRH (gonadotropin release hormone) - FSH and LH
GHRH (growth hormone releasing hormone)
GHIH (growth hormone inhibiting hormone)

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17
Q

What is the difference between tropic and trophic hormones?

A

Tropic: stimulate/inhibit release of other hormones
Trophic: hormones affecting growth

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18
Q

What is TSH?

A

AP gland:
Thyroid stimulating hormone
(secretion of thyroid hormone)

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19
Q

What is ACTH?

A

AP gland:
Adrenocorticotropic hormone
(secretion from adrenal cortex)

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20
Q

What is LH?

A

AP gland:
Luteinising hormone
(ovulation/sex hormone secretion)

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21
Q

What is FSH?

A

AP gland:
Follicle stimulating hormone
(egg/sperm development)

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22
Q

What is PRL?

A

AP gland:
Prolactin
(mammary gland development, milk secretion)

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23
Q

What is GH?

A

AP gland:
Growth hormone
(Growth and energy metabolism)

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24
Q

What is the relationship between the hormones and the glands?**

A

Slide 12

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25
Q

How are the pathways of hormonal production regulated?**

A

Negative feedback (short/long loops)

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26
Q

What stimulates the hypothalamus to produce CRH and then ACTH?*

A

Stress (pain, hypoglycaemia, low BP) produces CRH and acts on the anterior pituitary (via hypophyseal portal system) which produces ACTH, and which then stimulates adrenal cortex to produce cortisol.

27
Q

What controls growth?

A
  • Genetics
  • Environment
  • Nutrition
  • GROWTH HORMONE
28
Q

What is necrosis?

A

Cell death by damage

29
Q

What is atrophy?

A

Decrease in cell size/number

30
Q

What is apoptosis?

A

Programmed cell death

31
Q

What is hypertrophy?

A

Increase in cell size

32
Q

What is hyperplasia?

A

Increase in cell number

33
Q

Where is growth hormone produced and what stimulates its production?

A
  • Anterior pituitary
  • Stimulated by hypothalamic GHRH
  • Inhibited by hypothalamic somatostatin
34
Q

How are growth-promoting effects triggered?

A

Via insulin-like growth factors (somatomedins)

35
Q

Which cells produce IGFs and why?

A

Cells of liver and skeletal muscle produce and secrete IGF in response to growth hormone secreted from the anterior pituitary

36
Q

Is GH an active hormone?

A

No - it has a signal peptide that must be cleaved before proper folding

37
Q

What is the function of GH?*

A

Stimulating bone growth

  • Length & width before epiphyseal closure
  • Width after epiphyseal closure (maintain bone mass)
38
Q

What are the direct and indirect effects of GH?

A
  • Direct: GH receptors
  • Indirect: Producing IGFs
  • Local tissue growth (muscle)
39
Q

What is the function of IGF?

A

Bone and cartilage growth stimulation

40
Q

What do GH and IGFs do in adults?

A

Maintain muscle and bone mass
Promoting healing and tissue repair
Modulating metabolism and body composition

41
Q

How is GH secretion controlled?

A

Via hypothalamus

  • GHRH: + GH secretion
  • Somatostatin: - GH secretion
42
Q

How does sleep affect GH secretion?*

A
  • Deep sleep = a lot of GH
  • REM = less GH secretion
    (Why uninterrupted sleep important in children)
43
Q

How do stress and exercise affect GH secretion?

A 
Stress = GH secretion
Exercise = GH secretion
44
Q

How do glucose and FAs affect GH secretion?

A
  • Low glucose/FA = Increase

- High glucose/FA = Decrease

45
Q

How do fasting and obesity affect GH secretion?

A
  • Fasting: + Secretion

- Obesity: - Secretion

46
Q

How is GH secretion regulated?*

A

Short loop and long loop negative feedback

47
Q

What mediates long loop feedback and how?*

A
  • IGFs
  • Inhibit release of GHRH
  • Stimulate somatostatin release, which therefore inhibits GH release from anterior pituitary
48
Q

What mediates short loop feedback?

A

GH itself via stimulating somatostatin release

49
Q

What does growth hormone deficiency cause in children and what are the defining features?*

A

Pituitary dwarfism

  • Proportionate
  • Hormone can be absent or deficient
  • Respond to GH
  • Height below 3rd percentile
  • Slow growth
  • Delayed sexual development
50
Q

What are the causes of pituitary dwarfism?

A

Damage to skull due to a traumatic injury which then causes damage to pituitary gland and release of GH

51
Q

What is acromegaly and what causes it?*

A

Large extremities (hands/feet/jaw) caused by excess growth hormone

Caused by a pituitary adenoma developing in adulthood and causing widening

52
Q

What is gigantism and what causes it?*

A

Prolonged bone growth before epiphyseal plate fusion due to excess GH

Caused by pituitary adenoma in childhood

53
Q

How does GH exert effects on cells?*

A
  • GH receptors activate Janus kinases (JAKs, tyrosine kinase receptors)
  • GH binding causes receptor dimerisation
  • Causes change in conformation and activates receptor
  • Autophosphorylation of own residues
  • Activates transcription of IGF and signalling pathways
54
Q

What are the differences between IGF1 and IGF2?

A

IGF1: adults
IGF2: foetal growth

55
Q

How are IGFs modulated?

A

Binding proteins (modulate bioavailability)

56
Q

What do IGFs modulate?

A
  • Hypertrophy
  • Hyperplasia
  • Protein synthesis +
  • Lipolysis +
57
Q

What are IGF actions?

A
  • Autocrine/paracrine (skeletal muscle)

- Endocrine (liver)

58
Q

Discuss the insulin like growth factor receptors. ***

A

SLIDE 25

  • Hybrid receptors (1/2 insulin 1/2 IGF1 receptors, etc)
  • Mitogenic and metabolic effects
59
Q

What is the action of insulin?

A

Somatic growth + IGF interaction

60
Q

What is the action of thyroid hormones?

A

CNS development and GH secretion

61
Q

What is the action of androgens?

A

Pubertal growth, increase in muscle mass, closure of epiphyseal plates

62
Q

What is the action of oestrogen?

A

Decrease of somatic growth and closure of epiphyseal plates

63
Q

What is the action of glucocorticoids?

A

Inhibition of somatic growth

Metabolism, Endocrinology, Haematology (16 decks)

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