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Diabetes & Endocrinology > Introduction to Endocrinology > Flashcards

Introduction to Endocrinology Flashcards

1
Q

What is the endocrine system?

A

The system that integrates and controls organ function via hormones from tissues or glands which are then carried in the blood to target organs distal from the site of the hormone synthesis where they influence the activity of the target organ

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2
Q

What are paracrine chemicals?

A

Act locally at the site of synthesis

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3
Q

What are autocrine chemicals?

A

Act on or in the same cell that synthesised them e.g. cytokines

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4
Q

What are exocrine chemicals?

A

Released from exocrine glands via ductus to the external environment and the GI tract e.g. saliva, sweat, bile

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5
Q

How do the basics of the endocrine communication operate?

A

Hormones travel in the blood to their target organs and/or tissues

Tissues detect the hormones via specific receptors for that chemical on or in the cells, if there are no receptors present there is no response

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6
Q

What is the link between the neural and endocrine systems?

A

The neuroendocrine systems are the combination of the neural and endocrine systems, where nerves release hormones and they travel in the blood to the target organs

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7
Q

Describe the specificity of tissues to organs

A

Generally tissues are highly specific, despite the perfusion of many hormones throughout the circulation

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8
Q

Give some examples of endocrine functions both in physiological systems and as distinct glandular systems

A

Physiological - reproductive, renal, GI

Glands - thyroid, adrenal, pituitary

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9
Q

Describe the secretion of endocrine hormones

A

Secretion is by a cell or group of cells and is directly into the blood, where the hormones are directed to the distant targets

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10
Q

Describe the concentration of endocrine hormone required to exert their effect

A

Very low concentrations required to have effect

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11
Q

What is often the termination stage that ceases the function of endocrine hormones?

A

Action of a negative feedback loop

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12
Q

What are the three classifications of endocrine hormone?

A

Peptide or Protein - most common

Steroid

Amine

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13
Q

From what are all steroid hormones derived?

A

Cholesterol

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14
Q

From what are all amine hormones derived?

A

One of two amino acids, either tyrosine or tryptophan

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15
Q

Give some examples of peptide hormones

A

TRH
FSH
Insulin

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16
Q

At what point are peptide hormones synthesised?

A

In advance of need and stored in vesicles until required

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17
Q

Describe the stages of the synthesis of peptide hormones

A

The initial protein produced by the ribosome contains at least one copy of the active hormone and is called the preprohormone

These are then cleaved into smaller units in the RER and are called prohormones

These prohormones are then packaged in vesicles in the golgi apparatus with proteolytic hormones which breakdown the prohormone into the active hormone and other fragments

The hormones are stored in these vesicles until required

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18
Q

Are peptide hormones water soluble?

A

Yes

19
Q

Can peptide hormones cross cell membranes? Why?

A

No, because they are water soluble

20
Q

What do peptide hormones do as they are unable to cross cell membranes?

A

Bind to membrane bound receptors on the target cell

21
Q

Are the responses caused by peptide hormones usually fast or slow?

A

Usually fast - seconds to minutes

22
Q

What are the two different pathways that peptide hormones may modulate once attached to a cell receptor?

A

GPCR pathway

Tyrosine Kinase Linked pathway

23
Q

Are peptide hormones hydrophilic or hydrophobic?

A

Hydrophilic

24
Q

What is the result and response speed if a peptide hormone modulates a GPCR pathway?

A

There is activation of a 2nd messenger system and modification of the existing protein

Rapid response

25
Q

What is the result and response speed if a peptide hormone binds to and modulates a tyrosine kinase linked pathway?

A

Gene expression is altered

Slower, longer lasting activity

26
Q

At what stage are steroid hormones synthesised?

A

Directly as needed rather than in advance

27
Q

Are steroid hormones lipophilic or lipophobic?

A

Highly lipophilic (lipid soluble)

28
Q

What happens once steroid hormones have been synthesised?

A

They diffuse across the membrane into the ISF and the blood

29
Q

Are steroid hormones easily soluble in water?

A

No, they are transported with carrier proteins like albumin, stabilising their transport and protecting them from enzymatic degradation, massively increasing their half life - 60-90 minutes versus 2 mins for adrenaline

30
Q

Where are steroid hormones produced?

A

The gonads, placenta, kidney, adrenal cortex

31
Q

Can steroid hormones cross the cell membrane?

A

Yes, easily, both in and out

32
Q

Where in/on the cell are receptors for steroid hormones?

A

Within the cell as the hormones can easily pass in and out of the cell

33
Q

What is the term for the effect that steroid hormones have on a cell? What is the result of this?

A

Genomic effect - this has a knock-on effect in altering the proteins

34
Q

What is the usual timescale for the effect of steroid hormones?

A

Relatively slow between release and biological effect - hours to days

35
Q

What is the only amine hormone not derived from tyrosine? What is its role?

A

Melatonin - regulating circadian rhythm

36
Q

Is the bound steroid hormone or the unbound free hormone in the physiologically relevant?

A

The free hormone - the vastly smaller portion

37
Q

Which two quantities make up the total plasma hormone content?

A

Free hormone + complexed hormone

38
Q

What are the functions of hormone carrier proteins?

A

Transport hormones in the plasma by increasing solubility

Protecting hormones from degradation

Increasing hormone half life

39
Q

How does the removal of hormone from the blood take place? Where?

A

By excretion or metabolic transformation and mainly occurs in the liver and kidneys

40
Q

Do steroid and thyroid hormones take more or less time than peptide and catecholamine hormones to be excreted/metabolised? Why?

A

Steroid and thyroid hormones take considerably more time - hours to days, because they are bound to carrier proteins

41
Q

What is an important principle in monitoring/testing hormone levels?

A

Single/instantaneous values may be misleading and so 24 hour monitoring is required to provide a clinically useful picture

42
Q

What is endocrine up-regulation?

A

An increase in the number of hormone receptors on target tissues in response to prolonged exposure to low levels of plasma hormone

43
Q

What is endocrine down-regulation?

A

A decrease in the number of hormone receptors on target tissues in response to prolonged to high levels of plasma hormone

Diabetes & Endocrinology (18 decks)

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