L68 Endocrinology Basics Flashcards

1
Q

What are characteristics of classical endocrine glands

A

Ductless
Secrete into bloodstream/EC space
entire organ dedicated primariy to endocrine function

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2
Q

What are non classical endocrine organs and what do they secrete?

A
Brain/Hypothalamus: releasing hormones
Kidney: Renin, Vitamin D, EPO
Heart: ANP, BNP
Liver: IGF-1
GI: Stomach: Serotonin, Ghrelin
Adipose: Leptin
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3
Q

What are the 3 mechanisms of hormone action?

A

Endocrine: secrete into blood to act on downstream target tissues
Paracrine: secrete into interstitial space and act on nearby cells
Autocrine: secrete into interstitial space and act back on same cell

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4
Q

What type of signaling is neurotransmitter transmission?

A

Paracrine

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5
Q

How do hormone binding proteins affect hormone half lives?

A

They increase it by binding hormones in blodo to facilitate transport

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6
Q

Which hormones use hormone binding proteins?

A
Steroid hormones (lipophilic)
IGF-1, GF, T4/T3
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7
Q

What hormones do SHBG (sex hormone binding globulin) bind?

A

Estrogen and TEstosterone

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8
Q

What hormones do CBG (Corticotrophin binding protein) bind?

A

Cortisol/Corticosterone

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9
Q

What hormones do TBG ad TTR (Thyroid Binding Globulin and Transthyretin) bind?

A

Thyroid hormones

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10
Q

Which hormones are considered bioavailable?

A

Free/Unbound and Albumiin bound hormones

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11
Q

Which hormones are considered free?

A

Unbound/free

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12
Q

What role does albumin play in hormone transport in blood?

A

Binds nonspecifically to lipophilic hormones in blood

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13
Q

How is hormone delivered to atarget cell?

A
  1. Steroid hormone released at membrane -> cross lipid bilayer-> intracellular target
  2. Hormone/Protein complex binds to MEGALIN -> Form endocytic vesicle-> hormone dissociates and is released from vesicle
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14
Q

What is required for hormones to elicit their effects?

A

Receptors

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15
Q

What is the difference between specificity and affinity?

A

specificity: ability to distinguish between similar substances (Ki: ability to displace ligand at 50% of max activity=> smaller ki->higher specificity)
Affinity: binding affinity (Kd: ligand concentration that takes up 50% of binding sites; smaller number-> higher affinity)

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16
Q

What are lipophobic receptor characteristics?

A

Bind to cells urface receptors
Use 2nd messenger signaling pathways
Rapid internalization/degradation

17
Q

What are xamples of lipophobic receptors?

A

GPCR: protein hormones
Receptor linked Kinases: EPO, GH, Prolactin
Receptor Kinases: Insulin, ANP

18
Q

What are lipophilic receptor characteristics?

A
Bind to intracellular receptors
Bound to large chaperone proteins in cytoplasm
Slow biological response
Repress/Activate Transcription
Example: Thyroid hormone receptor
19
Q

How does the thyroid hormone receptor work?

A

Thyroid hormone binds to nuclear receptors
Nuclear receptors not bound to ligand repress transcription-> binding of thyroid hormone allows activation of gene transcription4

NOTE: Thyroid hormones are NOT steroid hormones!

20
Q

Describe how Steroid hormones and receptors work in a cell

A

Steroid hormones freely enter cells -> bind to intracellular receptors that are associated with chaperone proteins -> chaperones dissociate with hormone binding -> hormone/receptor complex translocate to nucleus-> act as transcription factor for genes

21
Q

What factors affect hormone bioavailability?

A

Hormone transport
Target tissues: receptors, chaperone proteins
Hormone Synthesis/Release
Regulatory Mechanisms