Endo 3 Flashcards

1
Q

What are the steps to the calcium cycle (draw if possible)

A

Dietary Ca –> feces
|
Absorbed in plasma with Vitamin D and PTH
|
Calcitonin helps: 1. bone deposit or 2. Kidney filtration

  1. Can be Reabsorbed with PTH into plasma
  2. When filtered: will be lost in urine or reabsorbed in plasma with PTH
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2
Q

Where are the parathyroid hormone released from?

A

One of the four parathyroid hormone behind the thyroid

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3
Q

What is the general structure of PTH

A

84 polypeptide, only the 34 terminal are important PTH activity as they are the ones that bind to the receptors to be activated

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4
Q

What is the half-life of PTH

A

3-18 minutes depending on the individual, meaning it is a tightly regulated hormone

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5
Q

What is the main function of PTH? how does it do so?

A

Increase the concentration of plasma calcium
1. Bone resorption: increase demineralisation
2. Kidney:
…….2.1 increase reabsorption
…….2.2 stimulate the synthesis of 1.25D3 (active vit D)
3. Facilitate the reabsorption of Ca in the gut

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6
Q

How is PTH release controlled?

A

The circulating concentration of Calcium is the stimuli of the parathyroid receptors to adapt the amount of PTH released

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7
Q

Explain the calcium cycle (PTH actions) in LOW calcium situations

A

LOW Ca in blood
|
Parathyroid gland stimulation
|
Increased PTH (1.bone 2.kidney)

  1. More Ca reabsorbed with PTH into plasma (bone breakdown)
  2. More Ca is reabsorbed and low Ca in urine
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8
Q

Explain the calcium cycle (PTH actions) in HIGH calcium situations

A

HIGH Ca in blood
|
Parathyroid gland receives negative feedback
|
Decreased PTH (1.bone 2.kidney)

  1. More Ca is deposited with calcitonin, less is reabsorbed
  2. Less Ca is reabsorbed and high Ca in urine (calcitonin)
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9
Q

What is hypoparathyroidism and what are the associated symptoms?

What is an example of life-threatening symptom?

A

Low levels of PTH in the blood

-Hypocalcemia
-Decreased production of active vitamin D
-Tetany (convulsion due to neural over excitability, muscle spasms)

Ex: tetany in the laryngeal muscles can lead to death by asphyxiation

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10
Q

What is the treatment for hypoparathyroidism?

PTH CONTROLS…

A

Administration of 1.25 vitamin D and calcium supplements

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11
Q

What is hyperparathyroidism and what are the associated symptoms?

A

High levels of PTH in circulation, often caused by parathyroid adenoma (benign growth)

-High production of Vit D
-Elevated blood Ca
-Formation of kidney stones (irregular deposit)
(severe cases can effect arteries and bones)

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12
Q

What is the treatment for hyperparathyroidism?

replacement of what

A

Removal of the parathyroids and replacement therapy of 1.25 D3 and Ca

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13
Q

Where can vitamin D be found?

A
  1. dietary sources: cod liver oil, fatty fish
  2. synthesized from a cholesterol metabolite
    • UVB light in skin (not during winter)
      -reaction in liver and kidneys
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14
Q

What are the functions of vitamin D?

A
  • Increase Ca absorption in the intestines
  • Regulate the immune system (anti-inflammatory)
  • Anticancer
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15
Q

How is vitamin D regulated?

A

Vitamin D synthesis is increased when there is low circulating Ca and high PTH

Synthesis is decreased in the presence of high circulating Ca

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16
Q

What can the absence of UVB lead to? how is it different in growing individuals vs adults?

A

a lack of UVB will inhibit vitamin D synthesis and cause a deficiency, as well as deficient bone growth

Growing: causes rickets
Adults: Osteomalacia (soft bones from lack of mineralised Ca)

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17
Q

What are both ways a vitamin D deficiency can seen in the physiology (genetic defects)?

A
  1. lack of vitamin D receptors (can’t have replacement therapy, recognizable by lack of hair)
  2. No enzyme for the production of 1.25D3
18
Q

What is the role of calcitonin? How is it done?

A

Lower plasma calcium:
1. Promotes Ca transfer from blood to bone
2. Increase urinary excretion of Ca

19
Q

Of the three calcium controlling hormones (PTH, calcitonin and 1.25D3), which one is of lesser importance?

A

Calcitonin

20
Q

What are the two distinct tissues of the adrenal gland?

A

The cortex and the medulla

21
Q

Name the histologic appearance, origin and function of the cortex of the adrenal gland

A

Histology: large lipid-containing epithelial cells
Origin: derived from the mesoderm
Function: Produces steroid hormones (glucocorticoids, mineralocorticoids and progestin)

22
Q

Name the histologic appearance and origin of the medulla of the adrenal gland

A

Histology: Chromaffin cells (fine brown granules when fixed with potassium)
Origin: derived from the neural crest

Forms catecholamines (NE and E)

23
Q

There are three morphologically and functionally different layers to the adrenal cortex. Why is that? WHat do they do?

A

The different layers have different enzymes. A layer can only produce what it has the hormones for:

  1. Aldosterone
  2. Cortisol
  3. Glucocorticoids, progestin, androgens and estrogen
24
Q

What is the synthesis if adrenal steroids controlled by?

A

ACTH (adrenocorticotropin) a pituitary hormones

25
Q

What is the function of the steroid hormones released from the adrenal gland?

A

Regulate the transcription of receptors specific to the steroid hormone (remember intra cellular receptor)

26
Q

What two things vary a target tissue response to a steroid hormone?

A
  1. Each hormone brings on its specific hormone transcription
  2. A same hormone will have different reactions on different target tissue (overlap)
27
Q

What is the primary function of aldosterone?

A

[Sodium metabolism]
Increase the reabsorption of Na+ in the kidney (and plasma concentration of K+ and H+ to balance Na+)

28
Q

Even with aldosterone, Na+ can’t be uptaken on its own since the exchange has to be done in a _______.
How is that done?

A

Electrochemically neutral manner:
1. NaCl
2. Na in // K or proton out

29
Q

What are the 5 functions of glucocorticoids?

A
  1. Salt retention
  2. Effects the protein and carbohydrate metabolism
  3. Effects the lipid mechanism
  4. Anti-inflammatory
  5. Effects on bones
30
Q

How do glucocorticoid hormones affect salt retention?

A

Some action, but less effective than aldosterone

31
Q

How do glucocorticoid hormones affect the protein and carbohydrate metabolisms?

A

-Stimulates the synthesis of enzymes that break down muscle proteins
-Amino acids enter the liver and are converted to glucose and glycogen.
-Decrease glucose uptake, which INCREASES BLOOD GLUCOSE LEVELS, and increased insulin production

32
Q

How do glucocorticoid hormones affect the lipid metabolism?

A

-Maintain or increase lipid breakdown (lipolytic) in adipose tissue cells resulting in more lipid accessible to muscle as fuel or causing hyperlipidemia

33
Q

How do glucocorticoid hormones affect inflammation reactions?

A

-Inflammation can have fundamental changes in the metabolism, glucocorticoids help repress that change by acting as anti-inflammatories

34
Q

How do glucocorticoid hormones affect bones?

A

The protein catabolic effects of the hormone also decreased the protein matrix of bones. There can be an increased loss of Ca+ leading to osteoporosis

35
Q

How is glucocorticoid secretion controlled?

A

ACTH and a negative feedback loop to the hypothalamus and the pituitary gland

36
Q

What can happen in cases of enzyme deficiency for cortisol production?

think ffedback

A

Low cortisol stimulates ACTH production. Because cortisol is not produced, ACTH production will be unchecked and can cause congenital adrenal hyperplasia (acts like a non-toxic groiter)

37
Q

What is the treatment for an enzyme deficiency for cortisol production?

A

Administration of cortisol to
(i) correct the deficiency
(ii) normalize ACTH production

38
Q

What is the rhythm of plasma cortisol and ACTH release?

When will that rhythm be abolished?

A

a DIURNAL rhythm:
minimum at midnight and maximum in the morning

Under stress or Cushing’s disease

39
Q

When is CRH, ACTH and cortisol release increased? What does it affect?

A

Released during stress (ex., running)
It provides energy via the protein metabolism, but also prevents wound healing

40
Q

What are the effects of constant high levels of stress?

A

Glucocorticoids will lead to increased blood glucose (diabetes), decreased immune system, loss of bone, etc..