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Pituitary tumour EAR:1 > Overview and hormonal mechanisms > Flashcards

Overview and hormonal mechanisms Flashcards

1
Q

What is a hormone

A

Secreted directly into blood stream from ductless endocrine gland

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2
Q

What is the Thyroid -stimulating hormone (TSH) and where is it released from

A

Released from ant. pituitary gland and acts on thyroid gland. It regulates the production and secretion of thyroid hormones T3 and T4

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3
Q

What are autocrine messengers and an example of this

A

Travels by itself into the interstitial fluid which means it is able to act on the same cell that made that hormone

-Prostaglandins

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4
Q

What are paracrine messengers and example

A

Substance secreted by one cell and travels short distance to a cell nearby such as a neighbouring cell and acts on that

Somatostatin

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5
Q

What are neuroendocrine hormones and when are they secreted?

Examples

A

Nerve cell secretes a hormone which travels some distance within circulation. Hormone is stored in axon terminal until it is ready for secretion

Oxytocin and ADH (both from posterior pituitary gland)

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6
Q

What are neurotransmitters

A

Secreted when there’s an action potential in that neurone and goes to an adjacent neurone e.g. Acetylcholine

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7
Q

What are peptide hormones

A

Chains of amino acids

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8
Q

Where are peptide hormones excreted from

A

HYpothalamus

Anterior and posterior pituitary gland

Pancreas

GIT

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9
Q

Where are steroid hormones derived from

A

Cholesterol

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10
Q

What are some examples of steroid hormones

A

Cortisol

Aldosterone

Sex hormones

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11
Q

What are examples of hormones derived from tyrosine

A

Thyroid hormones and catecholamines

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12
Q

What are examples of Eicosanoid hormones

A

Prostaglandins

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13
Q

How are peptide hormones synthesised and secreted

A

Same way a normal protein is

  • Gene for peptide hormone is transcribed into mRNA
  • mRNA is translocated into cytoplasm and translation occurs
  • Translation takes place on ribosome
  • Ribosome is attached to ER and forms RER
  • Preprohormone is formed at first. It is hydrophobic and needs further processing and packaging
  • Post translational modification takes place (e.g. protein folding, disulphide bridge forming and glycosylation)
  • By the time prehormone gets to Golgi, prohormone is formed
  • IN Golgi, there is additional processing, cleaving and packaging in secretory granules
  • Hormone is now in its mature state

Hormone is stored until stimulus comes

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14
Q

How are steroid hormones formed and excreted from cell

A

Biosynthetic enzymes convert cholesterol into steroid hormone. Cholesterol complex Is lipid soluble so is able to pass through the cell and are not stored in cells

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15
Q

What do steroid hormones need in order to be transported in circulation

A

Be bound by plasma proteins

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16
Q

Why are steroid hormones not stored

A

Because they are lipid soluble and so diffuse out of cells

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17
Q

If you need an increase in steroid hormone, what needs to happen? and why

A

There needs to be an increase in synthesis of hormones because it is not stored

18
Q

If you need an increase in peptide hormone, what needs to happen? and why

A

Secretion is regulated by release of pre made peptide hormones because they are stored in cells

19
Q

How does the half life of peptide hormones compare to steroid hormones and why

A

Peptide- MInutes
Steroid- Hours- days

Because peptide hormones exist as free hormones so they are susceptible to protease whereas steroid hormones are bound to plasma proteins by weak, reversible bonds

20
Q

How are steroid hormones able to bind to receptors even though they are bound to plasma proteins

A

Theres a small proportion of them which are free and so are able to bind

21
Q

Why are peptide hormones not readily available to cross the lipid bilayer and why?

-How do they overcome this

A

They are hydrophilic

Plasma membrane receptors mediate their effects (G protein coupled receptors and tyrosine kinase kinked receptor)

22
Q

Which membrane receptors mediate the effects of peptide hormones and how do they do this

A

G protein coupled receptors
Tyrosine kinase linked receptor

-Mediate signal transduction which bring about a physiological response (altered activity of enzymes or ion channels or altered expression of specific proteins)

23
Q

Why are steroid hormones able to pass through the lipid bilayer and what are their effects mediated by

A

Because they are lipophilic

-Intracellular receptors

24
Q

What do the intracellular receptors act as inside the cell

A

Hormone-regulated transcription factors. They increase or decrease transcription so therefore have an effect on the associated functions of that protein

25
Q

How are hormones metabolised

A

BY enzymes in liver, kidney and/or blood

Small proportion by target tissues

Excreted in urine and/or faeces

26
Q

What happens when peripheral levels get too high

A

Inhibit anterior pituitary hormone and decrease hypothalamus from releasing hormones which affect the anterior pituitary

27
Q

When the peripheral hormone levels get too high how does the long feedback loop get affected

A

The long feedback loop loop is less used

28
Q

What can be a cause of excess hormones (hyper secretion)

A

Tumour or immunological factor

29
Q

What can be a cause of lack of hormones (hyposecretion)

A

Genetic
Immunological attack Destruction by disease
Surgical removal

30
Q

what can be the cause of decreased target cell responsiveness

A

At level of receptor or downstream enzyme

31
Q

What is a primary defect

A

problem with gland that makes that hormone

32
Q

What is a secondary defect

A

Problem with something else higher up in the system

33
Q

How to investigate endocrine disorders

A

Signs and symptoms
Endocrine investigations (hormone levels)
-Single point (base-line)
-Dynamic or provocative test to check the integrity of feedback control
-Imaging

34
Q

When are stimulation tests used and how to do them

A

If suspect hypo secretion (failure to stimulate conforms hormone insufficiency)

-Increase a particular hormone

35
Q

When are suppression tests used and how to do them

A

If suspect hyper secretion (failure to suppress indicates autonomous secretion i.e. tumour)

-Give a hormone that suppresses the secretion of that hormone

36
Q

How to treat a hormone deficiency

A

Hormone replacement

37
Q

How to treat a hormone excess

A

Drugs to block production

38
Q

How to treat patient if there is decreased cell responsiveness

A

Drugs to enhance cellular response to hormone

39
Q

What is a primary cause of hormone disorders

A

Endocrine gland secreting hormone

40
Q

What is a secondary cause of hormone disorders

A

control by pituitary tropic hormone

Pituitary tumour EAR:1 (10 decks)

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