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Endocrine > Overview > Flashcards

Overview Flashcards

1
Q

Definition of endocrinology

A

The study of hormones and their glands of origin, their receptors, intracellular signalling pathways, and their associated diseases

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2
Q

Definition of hormone

A

A regulatory substance produced in an organism and transported in tissue fluids (i.e. blood) to stimulate a specific cellular tissue into action

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3
Q

Definition of endocrine

A

Glands which secrete hormones or other products directly into the blood

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4
Q

Definition of exocrine

A

Glands which secrete their products through ducts opening on to an epithelium rather than directly into the blood

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5
Q

Name the key organs of the endocrine system

A

Pituitary, thyroid, parathyroid, adrenal glands, pancreas, ovaries, testes

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6
Q

What is the endocrine hormone action?

A

Blood borne, acts at distant sites

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7
Q

What is the paracrine hormone action?

A

Acting on adjacent cells

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8
Q

What is the autocrine hormone action?

A

Feedback on the same cell that secreted the hormone

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9
Q

Give features of the functional anatomy of water-soluble hormones

A
  • Transported unbound
  • Bind to surface receptor on cells
  • Have a short half-life
  • Are cleared fast
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10
Q

Give examples of types of water-soluble hormones

A

Peptides and monoamines - both stored in vesicles

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11
Q

Give features of the functional anatomy of fat-soluble hormones

A
  • Transported bound to protein
  • Diffuse into cells
  • Have a long half-life
  • Are cleared slowly
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12
Q

Give examples of types of fat-soluble hormones

A

Thyroid hormones and steroids (synthesised on demand)

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13
Q

Name the four classes of hormones

A
  1. Peptides
  2. Amines
  3. Iodothyronines
  4. Cholesterol derivatives and steroids
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14
Q

Give features of peptide hormones

A
  • Vary in length
  • Stored in secretory granules in the cytoplasm
  • Hydrophilic and water soluble
  • Cleared by the tissue or circulating enzymes
  • Synthesised first as preprohormones then processed (by ER and Golgi) to prohormones
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15
Q

Describe how insulin is activated to cause glucose uptake

A
  1. Insulin binds to its receptors
  2. This causes the receptor to be phosphorylated
  3. The secondary messenger, tyrosine kinase is activated
  4. There is phosphorylation of the signal molecules
  5. Cascade of effect
  6. Glucose uptake
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16
Q

Give features of amine hormones

A
  • Water soluble
  • Stored in secretory granules
  • Released in pulses
  • Have rapid clearance
  • Synthesis = Phenylalanine -> L-Tyrosine -> L-Dopa -> Dopamine -> Noradrenaline -> Adrenaline
  • Rate limiting step is conversion to L-DOPA
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17
Q

What does cortisol do in relation to noradrenaline?

A

Converts noradrenaline to adrenaline

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18
Q

Name some physiological reactions that alpha receptors are responsible for

A
  • Vasoconstriction
  • Pupil dilatation
  • Bowel muscle and anal sphincter contraction
  • Sweating
  • Anxiety
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19
Q

Name some physiological reactions that beta receptors are responsible for

A
  • Vasodilation
  • Increase in HR
  • Increase force of contractility
  • Relaxation of bronchial smooth muscles
20
Q

How does adrenaline activate the secondary messenger system?

A
  • Binds to alpha receptors: Protein kinase C is converted to active protein kinase C and IP3 stimulates calcium release to exert tissue functions
  • Binds to beta receptors: Adenyl cyclase converts ATP to cyclic AMP, activation protein kinase to exert its function on the cell
21
Q

Which receptors do adrenaline, noradrenaline and dopamine bind to?

A
  • Adrenaline: all adrenergic receptors
  • Noradrenaline: α1, α2, β1 receptors
  • Dopamine: α1, α2, β1 and the two dopamine receptors
22
Q

Are thyroid hormones water-soluble and what is the structural consequence of this?

A

No so they must be bound to a protein. 99% of thyroid hormones are bound to thyroid-binding globulin (TBG)

23
Q

Compare T3 to T4

A
  • T3 (aka triiodothyronine) is more active than T4

* T4 (aka thyroxine) is less active than T3 but more of it is produced

24
Q

How are T3 and T4 stored?

A

Iodothyrosines are conjugated to give rise to T3 and T4 which are stored in colloid and bound to thyroglobin

25
Q

Why can T4 be thought of as a reservoir for T3?

A

Because most of T3 is made from the breakdown of T4 to T3 outside the thyroid gland (only 20% of T3 in circulation is secreted by the thyroid)

26
Q

What class of hormone does Vitamin D fall under?

A

Cholesterol derivatives and steroids

27
Q

Give 3 features of vitamin D

A
  1. Fat soluble vitamin
  2. Enters the nucleus directly to stimulate mRNA production
  3. Transported by Vitamin D binding protein
28
Q

How is vitamin D produced by sunlight exposure?

A

7-dehydrocholesterol -> cholecalciferol (vitamin D3) -> (in the liver) -> 25-hydroxyvitamin D3 -> (in the kidney) -> 1,25-dihydroxyvitamin D3

29
Q

Name the 5 key adrenocortical and gonadal steroids

A
  • Cortisol
  • Aldosterone
  • Testosterone
  • Oestrogen
  • Progesterone
30
Q

Are adrenocortical and gonadal steroids protein bound?

A

Yes, 95% are

31
Q

What is the action of steroids?

A

• EITHER:
enter cell and directly bind to the nucleus and stimulate mRNA production (e.g. oestrogen)
• OR:
1. Diffuse through plasma membrane and binds to cytoplasm receptor
2. Receptor-hormone complex enters the nucleus
3. In the nucleus it binds to glucocorticoid response element (GRE)
4. Binding initiated transcription of gene to mRNA
5. mRNA directs protein synthesis

32
Q

Where are the 3 receptor locations for hormones and what binds to them?

A
  1. Cell membrane (for water-soluble hormones)
    - Peptides/amines e.g. insulin
    - Allows for cell selectivity
  2. Cytoplasm (for fat-soluble hormones)
    - Steroids (more lipid soluble so can cross the cell membrane)
    - Examples: glucocorticoids (e.g. cortisol), mineralocorticoids (e.g. aldosterone), androgens (e.g. testosterone), progesterone
  3. Nucleus (for fat-soluble hormones)
    - Thyroid hormones
    - Oestrogen
    - Vitamin D
33
Q

Give the 4 ways that hormone secretion is controlled with examples

A
  1. Basal secretion = continuously/pulsatile
    - Continuous release e.g. prolactin
    - Pulsatile release e.g. insulin
  2. Circadian rhythm e.g. ACTH, prolactin, GH, TSH and cortisol
  3. Release inhibiting factors e.g. Dopamine inhibits prolactin, the sum of the positive and negative effects (GHRH (+) and somatostatin (-) on GH)
  4. Releasing factors
    - Humoral stimulus = hormone release caused by altered levels of certain critical ions or nutrients e.g. low Ca2+ stimulates PTH release
    - Neural stimulus = hormone release caused by another hormone (tropic hormones) e.g. hypothalamus secretes hormones to stimulate the pituitary gland to release hormones
34
Q

Give 5 ways that the action of hormones is controlled

A
  1. Hormone metabolism = metabolism increases to reduce function
  2. Hormone receptor induction
  3. Hormone receptor down regulation
  4. Synergism = combined effects of two hormones amplified
  5. Antagonism = one hormone opposes another hormone
35
Q

Definition of appetite

A

The desire to eat food

36
Q

Definition of hunger

A

The need to eat

37
Q

Definition of satiety

A

The feeling of fullness, disappearance of appetite after a meal

38
Q

What does BMI stand for and what are the units?

A

Body mass index - kg/m2

39
Q

What are the ranges for BMI?

A
  • < 18.5 = underweight
  • 18.5-24.9 = normal weight
  • 25.0-29.9 = overweight
  • 30.0-39.9 = obese
  • > 40.0 = morbidly obese
40
Q

What sort of stimuli stimulate appetite?

A

Olfactory, gustatory, cognitive and visual stimuli

41
Q

What is the role of stretch receptors in satiety?

A

They increase satiety by increasing the feedback on the brain

42
Q

What is the role of leptin and insulin in satiety and where are they produced?

A
  • They have a net effect of increasing satiety and reducing appetite
  • Leptin is secreted by white fat
  • Insulin is secreted by the pancreas
43
Q

Name the 4 main gut peptides involved in appetite regulation

A
  1. Ghrelin
  2. PYY
  3. Glucagon-like peptide 1 (GLP1)
  4. Cholecystokinin (CCK)
44
Q

What does ghrelin do and where is it secreted?

A
  • Increases appetite and stimulates GH release

* Secreted by the stomach

45
Q

What does PYY do and where is it secreted?

A
  • Inhibits gastric motility and reduced appetite

* Secreted by neuroendocrine cells in the ilium, pancreas and colon in response to food

46
Q

What does GLP1 do and where is it secreted?

A
  • Secreted by the small intestine

* Enhances insulin secretion

47
Q

What does CCK do and where is it secreted?

A
  • Delays gastric emptying and causes gallbladder contraction and insulin release
  • Causes satiety via the vagus nerve
  • Secreted by the duodenum
  • Receptors in the pyloric sphincter

Endocrine (7 decks)

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