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P1: Endo > Hormone Synthesis and Action > Flashcards

Hormone Synthesis and Action Flashcards

1
Q

What are peptides and proteins?

A

→ Water soluble
→ Made from large precursors
→ Prohormones

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2
Q

What are steroids and iodinated tyrosines?

A

→ Lipid soluble

→ Made from low weight molecular weight precursors

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3
Q

What is a pre pro hormone?

A

→ Signal sequence + prohormone

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4
Q

What is a prohormone?

A

→ Hormone + peptide sequence

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5
Q

What is the inactive form of vasopressin called?

A

→ Arginine vasopressin

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6
Q

What are the steps in insulin synthesis?

A

1) transcription to mRNA
2) Excision of introns to mRNA
3) Removal of signal sequence and formation of disulfide bonds in RER
4) Pre-pro insulin → pro insulin
5) Transferred to golgi and excision of C peptide

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7
Q

What is StAR?

A

→ Steroidogeneic acute regulatory protein

→ Protein that transports cholesterol to the inner mitochondrial membrane

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8
Q

How is cholesterol made into steroids?

A

→ Lipid stores in the cell
→ Stimulus activates a second messenger
→ Cholesterol transfers from cytoplasm into mitochondria
→StAR protein transports cholesterol to the inner mitochondrial membrane

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9
Q

What is cholesterol cleaved into and how?

A

→ Cleaved to pregnenolone

→ Side chain cleavage enzyme P450cc

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10
Q

What are the hormones cholesterol can be converted into?

A 
Cholesterol
↓
Pregnenolone
↓
Progesterone → Aldosterone
Hydroxylated progesterone → Cortisol + Androgens
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11
Q

What enzymes do androgens need and what do they do?

A

→ Aromatase

→ Converts androgens to estrogens

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12
Q

What is aromatase deficiency in men?

A

→ Unable to synthesize estrogens from androgens
→ No epiphyseal closure (bone development)
→ Long stature

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13
Q

What happens if children have aromatase deficiency?

A

Girls
→ Virilization of XX fetuses
→Ambiguous genitalia

Boys
→ Precocious puberty
→ Early sexual development

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14
Q

What are the 8 steps for the synthesis of thyroid hormones?

A

1) Active uptake of iodide into follicular cell
2) Transport across the apical membrane
3) Oxidation of iodide to iodinated intermediate by thyroid peroxidase
4) Iodination of tyrosine residues of thyroglobulin
5) Coupling of iodinated tyrosine residues
6) Storage of T3 and T4
7) Uptake of thyroglobulin droplets into follicle cell
8) release of T3 and T4

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15
Q

Where is iodide hormone stored?

A

→ Colloid

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16
Q

What is goitre?

A

→ Enlargement of the thyroid gland

17
Q

What is Graves disease?

A

Antibodies to the TSH receptor act on the thyroid gland
→ Stimulates excess thyroid hormones and can cause ophthalmopathy
Proptosis- eye bulging. the immune system attacks the muscles and fatty tissues around and behind the eye

18
Q

What are properties of peptide and protein hormones?

A

→ Water soluble → cell surface receptors
→ Activate second messengers and/or enzymes
→ Cytoplasmic and nuclear effects

19
Q

What are properties of steroid hormones?

A

→ Lipophilic
→ Intracellular receptors in cytoplasm or nucleus
→ Receptors are transcription factors

20
Q

What are the two surface receptors?

A

→ G protein linked receptors

→ Tyrosine kinase domains

21
Q

What is involved the G protein signalling pathway?

A

→ Adenyl cyclase
→ cAMP
→ PKA

22
Q

What is involved the PIP pathway?

A

→ PIP
→ DAG
→ IP3
→ Ca2+

23
Q

What are the major pathways in tyrosine kinase?

A

→ RAF/ MEK/ ERK
→ PI3 kinase / AKT
→ JAK/ STAT

24
Q

What is mTOR a target for?

A

→ Cancer drugs

Hormone Synthesis and Action

25
Q

What can mTOR go on to do after being phosphorylated?

A
  1. promoting of ribosome synthesis/protein synthesis
  2. inhibiting of protein degradation
  3. stimulating protein uptake and metabolism
26
Q

What are two conditions if you have a defective G coupled receptor?

A

→ Thyroid adenoma

→ Precocious puberty

27
Q

What are 2 conditions if you have a defective G protein?

A

→ McCune Albright syndrome

  • fibrous dysplasia of bone
  • cafe au lait pigmentation

→ Combined precocious puberty

28
Q

What is the C domain of steroid hormone receptors?

A

→ DNA binding region

29
Q

What are the functional domains of steroid receptors?

A

→ A-F

30
Q

What is the C domain made up of?

A

→ 2 zinc fingers

→ Slot into helix of DNA

31
Q

What are the steps for steroid hormone binding?

A

1) Hormone crosses cell membrane
2) Heat shock protein dissociates from receptor
3) hormone binds to receptor and dimerization occurs and translocate to nucleus
4) Binds to hormones response element on DNA
5) Along with other transcription factors, transcription is initiated

32
Q

What can kinases do?

A

→ Activate transcription factors

33
Q

What are the causes of goitre?

A

Lack of iodine in the diet leads to deficiency in T3 and T4 (hypothyroidism)​

Graves disease (hyperthyroidism)​

Thyroid adenoma

34
Q

How does low T3 and T4 cause goitre?

A

reduced T3 and T4 lead to lack of inhibition of TSH

TSH responsible for thyroid gland growth

P1: Endo (12 decks)

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