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Endocrinology > Introduction > Flashcards

Introduction Flashcards

1
Q

What is a hormone

A

The bioactive messenger secreted by an endocrine gland into the blood

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2
Q

What is cryptocrine

A

Molecules within the cell that have effects on the cell

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3
Q

Compare endocrine to nervous system

A

chemical into the blood vs chemical across a synapse
affects target cells in the body vs only affects innervated cells
effect takes place over a long time vs effects generated in ms

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4
Q

What are the classic endocrine glands from head to toe

A 
Pituitary 
Parathyroids
Thyroid
Pancreas
Adrenals
Gonads
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5
Q

What are the two categories of hormones

A

Protein/polypeptide and steroid

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6
Q

Give 3 features of protein hormones

A

Active hormone drains into the capillaries
Specific amino acid receptors take the hormone to the nucleus
Short-Lifespan

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7
Q

Give features of steroid hormones

A

Derived from a cholesterol backbone
2 groups: intact steroid nucleus or broken steroid nucleus
LDL taken into the cell by LDL receptors
Cholesterol taken from LDL and stored while esterified

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8
Q

Describe the process of protein hormone synthesis

A
  1. mRNA is transcribed in the nucleus
  2. translation on the RER into the prohormone
  3. pro hormone transported to the golgi
  4. packaging into vesicles with proteolytic enzymes
  5. enzymes cleave to form active hormone
  6. exocytosis when required
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9
Q

What is the pro hormone for ACTH

A

POMC = ProOpioMelanoCorticotrophin

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10
Q

How are proteins transported

A

Freely through the blood as they are water soluble

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11
Q

When is hormone not directly released to systemic circulation

A

From hypothalamus to Hypophyseal portal system

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12
Q

Describe the process of protein hormone signalling

A
  1. protein binds to the Gs receptor
  2. alpha subunit dissociates
  3. Activation of adenyl cyclase
  4. ATP converted to cAMP
  5. protein kinase A activation
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13
Q

Which cell will ACTH bind to

A

Adrenal corticol cell

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14
Q

How may protein hormone signalling lead to steroid hormone synthesis

A
  1. PKA activates cholesterol esterase
  2. cholesterol esterase converts esterified cholesterol to free cholesterol
  3. stAR transfers the cholesterol to the inner mitochondrial membrane
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15
Q

How are steroid hormones synthesised

A
  1. liberation of cholesterol by esterase
  2. stAR takes cholesterol to the inner mitochondrial matrix
  3. Pathway to form the mature hormone
  4. Synthesised hormone can pass freely through the membrane
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16
Q

How are steroid hormones stored and transported

A

Stored in the blood by binding to plasma proteins e.g. albumin

17
Q

What is the consequence of greater binding of steroid hormones

A

Slower clearance of the hormone from the blood

18
Q

Describe the dynamic equilibrium for steroid hormones

A

Dynamic equilibrium between the free (active) hormones and those that are bound to proteins. Even if hormones are heavily bound, free hormones will always be free to access tissue

19
Q

Apply dynamic equilibrium to pregnancy

A

In pregnancy, CBG levels rise and so the levels of cortisol increases to balance it

20
Q

Give an example of plasma binding proteins

A

CBG - cortisol
TBG - thyroid
SHBG - testosterone/ oestrodiol

21
Q

Describe the process of steroid hormone signalling

A
  1. The hormone can diffuse by passive diffusion into the cytoplasm
  2. Binding to a specific receptor
  3. Alteration of the transcript and protein synthesis
22
Q

Which cytoplasmic receptor doe cortisol bind to

A

Glucocorticoid receptors

23
Q

Why is homeostasis essential for hormones

A

Closed loop system that prevents excessive hormone action through negative feedback

24
Q

How does homeostasis occur for protein and steroid hormones

A

Hormone that is produced by the peripheral target organ feeds back to the organ that stimulated it

Endocrinology (9 decks)

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