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Physiology & metabolism > week 3 - endocrine control of metabolism > Flashcards

week 3 - endocrine control of metabolism Flashcards

1
Q

What are thyroid follicles?

A

spherical sacs that make up most of the thyroid

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2
Q

What THs (thyroid hormones) does the thyroid produce?

A

T4 - thyroxine aka tetraiodothyronine

T3 - triiodothyronine

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3
Q

what are thyroglobulin the precursors for and when are they produced

A

thyroid hormone

when thyroglobulin’s tyrosine residues are combined with iodine and the protein is subsequently cleaved.

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4
Q

What are some actions of TH (thyroid hormones)

A

In the adipose tissue - THs promote lipolysis

In the liver - promotes mitosis/ gluconeogenesis

In the heart - helps with cardiac output

In the brain - Helps with development and function

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5
Q

What are the types of hyPOthyroidism?

A

Primary hyPOthyroidism

secondary hyPOthyroidism

Tertiary hyPOthyroidism

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6
Q

What is primary hyPOthyroidism?

A

Failure of the thyroid gland, which causes the underactive thyroid

usually caused by Hashimoto’s thyroiditis - an autoimmune disease

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7
Q

What is secondary hyPOthyroidism?

A

failure of the pituitary gland, usually caused by a pituitary tumour

This leads to reduced TSH which causes an underactive thyroid

REMEMBER TSH (THYROID STIMULATING HORMONE) IS PRODUCED BY THE PITUITARY WHICH PROMOTES THE THYROID TO PRODUCE THs T3, T4

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8
Q

What is tertiary hyPOthyroidism?

A

Failure/disease of the hypothalamus causing reduced TRH (Thyrotropin Releasing Hormone)

This leads to an under active thyroid

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9
Q

what does central hypothyroidism refer to

A

thyroid hormone deficiency

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10
Q

what is central hypothyroidism due to and what does it result to

A

due to disorder of the pituitary and or hypothalamus

results in diminished thyroid-stimulating hormone (TSH) and or thyrotropin-releasing hormone (TRH)

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11
Q

what are some causes to central hypothalamus

A

classical: space-occupying lesions, radiation to the pituitary/hypothalamus, vascular disease

non-classical: traumatic brain injury, infection, inflammation

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12
Q

how is central hypothyroidism diagnosed and treated

A

CT and MRI scans
treated by surgery/radiotherapy

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13
Q

What else can cause the thyroid gland to be under active/not produce enough hormone?

A

lack of iodine in the thyroid gland, the thyroid gland is usually rich in iodine.

A tumour that causes the thyroid hormones to not work.

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14
Q

what is the difference between compensated and decompensated hypothyroidism

A

compensated- organs working
decompensated- organs failing

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15
Q

What is the link between cardiovascular disease and hyPOthyroidism?

A

HyPOthyroidism can cause dyslipidaemia (lipid buildup) in blood vessels leading to heart attack/stroke.

This is due to the low levels of thyroid hormones so metabolic processes aren’t able to take place properly.

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16
Q

What is a treatment option for hyPOthyroidism?

A

Synthetic thyroid hormone - a type of medication that reverses the symptoms of hyPOthyroidism and restores thyroid hormone levels.

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17
Q

What is hyPERthyroidism?

A

It is an excess in production and secretion of thyroid hormones, which causes an over active thyroid gland.

It is the opposite of hyPOthyroidism

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18
Q

What is thyrotoxicosis?
Related to hyPERthyroidism.

A

It is when you have excess thyroid hormones circulating around the body. It is caused by hyPERthyroidism

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19
Q

What is thyroiditis?

A

When the thyroid gland becomes inflamed so swells, leading to the release of pre-formed thyroid hormones

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20
Q

What is Graves Disease?

A

It is an autoimmune condition that leads to hyPERthyroidism.

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21
Q

How does Graves Disease lead to hyPERthyroidism?

A

the immune system creates an antibody (thyroid stimulating immunoglobulin) which mimics TSH.

  1. The antibody mentioned above attach to thyroid cells
  2. The antibody turns on these thyroid cells to produce the thyroid hormones T3, T4
  3. This leads to the overproduction of T3, T4 causing an over active thyroid gland, which is hyPERthyroidism.
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22
Q

What is a toxic adenoma?
And how does it lead to hyPERthyroidism?

A

It is a nodule (growth of abnormal tissue) in the thyroid gland which leads to the overproduction of thyroid hormones T3, T4

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23
Q

What is a toxic multi nodular gaiter?

A

It is where many masses / nodules cause an enlarged thyroid gland, leading to excess thyroid hormone production, which is hyperthyroidism

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24
Q

What is colloid and what happens to it if you have hyPERthyroidism?

A

Colloid is present in the thyroid gland and you start to lose colloid when you have hyPERthyroidism - linked to Graves Disease

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25
Q

What are some symptoms of hyPERthyroidism/

A

Weight loss, muscle weakness, palpitations, skin thinning etc

These are due to increases hyper metabolism due to the increased hormone secretion of the thyroid gland.

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26
Q

what does hypermetabolism do

A

induces weight loss and increased appetite

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27
Q

What is thyroid storm and what is it caused by?

A

It is an acute, life threatening complication of hyPERthyroidism.

It is caused by UNTREATED or UNDERTREATED hyPERthyroidism - e.g. if you stop taking your medication

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28
Q

How can you diagnose hyPERthyroidism?

A
  1. checking medical history / do a physical exam

2.rRadioactive iodine uptake / scan

  1. Blood tests to measure T4 and TSH levels. - low TSH and high T4 levels indicate hyPERthyroidism
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29
Q

Iodine is found naturally in the thyroid gland.

What is its purpose in the thyroid gland?

A

It plays an essential role in the functioning of a healthy thyroid.

It is used to control thyroid function.

30
Q

What is radioactive iodine uptake and how is it used to diagnose hyPERthyroidism?

CHECK IODINE DIAGRAM

A

It is a test that measures the amount of radioactive iodine taken up by the thyroid gland.

A gamma probe is placed over the thyroid gland to measure the amount of iodine radioactivity.

This is compared with the original amount of radioactivity. - anything above 35% after 24 hours is considered elevated and could be hyPERthyroidism

31
Q

What are the treatments for hyPERthyroidism?

A

Taking radioactive iodine
Anti-thyroid medications
Beta blockers
Surgery (thyroidectomy)

32
Q

Describe radioactive iodine
(treatment for hyPERthyroidism)

A

It is iodine taken by mouth, and it is absorbed by the thyroid gland.
The iodine causes the gland to shrink.

However, the iodine may cause thyroid activity to slow down too much that the thyroid becomes under active (hyPOthyroidism)

33
Q

Describe anti-thyroid medication
(treatment for hyPERthyroidism)

A

Medicines such as methimazole and propylithiouracil. They reduce symptoms of hyPERthyroidism.
Treatment lasts for around a year.

However, people may experience relapse. The drugs can cause liver damage, even leading to death.

34
Q

Describe beta blockers
(treatment for hyPERthyroidism)

A

These do not affect thyroid hormone levels however can treat other symptoms such as rapid heart rate, tremors etc.

35
Q

Describe the thyroidectomy surgery
(Treatment for hyPERthyroidism)

A

Where the doctor removes most of your thyroid gland/parathyroid glands (control level of calcium in the blood).
Only used if you are pregnant or can’t handle anti-thyroid medication.

However, it can damage your vocal chords/parathyroid glands (if PTglands aren’t taken out.)
You’ll also need lifelong levothyroxine treatment to supply blood with normal thyroid hormone levels. And may need medication if your parathyroid glands are removed.

36
Q

What do corticosteroids comprise of?

A

Glucocorticoids
Mineralocorticoids

37
Q

What are glucocorticoids?

A

They regulate carbohydrates
The main glucocorticoid is cortisol aka hydrocortisone

38
Q

What are mineralocorticoids?

A

They regulate electrolytes.
The main mineralocorticoid is aldosterone.

39
Q

How are cortisol and aldosterone steroids controlled?

A

They are controlled by ACTH and Angiotensin

40
Q

What is ACTH?

A

It is a hormone produced by the pituitary gland that tells the adrenal glands to produce cortisol.

41
Q

What is Addison’s disease - also known as primary adrenal insufficiency?

A

It is where the adrenal glands become under active.
It can occur when the adrenal glands become damaged.
Results in decreased levels of cortisol, aldosterone and androgens, which leads to an increase in ACTH

42
Q

What is secondary adrenal insufficiency?

A

It is where there is damage to the pituitary gland which produces ACTH, rather than damage to the adrenal glands.

Because of this, if the pituitary doesn’t make enough ACTH, then the adrenal glands don’t make enough cortisol, so the adrenal glands start to shrink and eventually not work.

43
Q

What is tertiary adrenal insufficiency?

A

This is where there is damage to the hypothalamus.
The hypothalamus produces CRH, which tells the pituitary to produce ACTH, which tells the adrenal glands to produce cortisol.

If the hypothalamus doesn’t produce enough CRH, the pituitary gland won’t produce enough ACTH, then the adrenal gland won’t produce enough cortisol, which leads to under active adrenal glands.

44
Q

What is cortisol?

A

Known as the stress hormone as it helps your body to respond to stress.

It also helps to:
control blood pressure/blood glucose

reduce inflammation

control metabolism.

45
Q

What 2 condition cause the lack of aldosterone?

A

Hyponatremia - where there is low sodium in the blood (remember aldosterone regulates electrolyte balance)
It can cause fatigue, confusion

Hyperalkemia - where there is high potassium levels in the blood. Can cause life threatening changes such as changes in heart rhythm.

46
Q

Why does hyperpigmentation in the skin occur?

A

because MSH and ACTH share the same precursor molecule POMC

47
Q

How can you diagnose Addisons,/primary, secondary, tertiary adrenal insufficiency?

A

Measure blood cortisol levels - not really a good way to test as cortisol may be low from time to time normally anyways.

Short synacthen test - where you are injected with a synthetic ACTH intramuscularly.
This can determine whether you have primary, secondary or tertiary adrenal insufficiency

48
Q

How can you treat adrenal insufficiency, Addison’s disease?

A

Daily doses of glucocorticoids and mineralocorticoids usually for life.

For women androgen replacement may be recommended for women.

The goal is to stabilise hormone levels and relieve symptoms.

49
Q

What is adrenal crisis?

A

It’s very severe adrenal insufficiency

50
Q

what are some symptoms of adrenal crisis

A

fever
syncope
convulsions
hypoglycaemia
hyponatremia
severe vomiting and diarrhoea

51
Q

What is Cushing’s syndrome?

A

It is when you have an overactive adrenal gland.
It is caused by having very high levels of cortisol.

52
Q

What are some possible causes of Cushing’s syndrome ?

A

A pituitary tumour aka Cushing’s disease.

An adrenal tumour

Taking medicines containing glucocorticoids aka cortisol

53
Q

What are some symptoms of Cushing’s syndrome?

A

Weight gain
increased fat around base of neck
wide purple stretch marks
easy bruising
weak muscles

54
Q

What complications can Cushing’s syndrome cause?

A

heart attack
stroke
hypertension (high blood pressure)
type 2 diabetes
Unhealthy cholesterol levels

55
Q

How can you diagnose Cushing’s syndrome?>

A

It can be hard to diagnose since the symptoms can be cause by other diseases.

However, you can still carry out:
Low dose dexamethasone suppression test (LDDST)

Late night salivary cortisol test

24 hour urinary free - cortisol test

56
Q

Describe what LDDST is
(test to see for Cushing’s syndrome)

A

Where the patient receives a low dose of dexamethasone (type of glucocorticoid) at 11.00 pm

Blood sample is taken following morning?

57
Q

What do the results of LDDST suggest?

A

Usually after taking dexamethasone, blood cortisol levels should drop.
However, cortisol levels that don’t drop suggest Cushing’s syndrome.

58
Q

What is the late night salivary cortisol test?
(test to see for Cushing’s syndrome)

A

It is where the cortisol levels in your saliva are measured in the late evening.

59
Q

What do the results of a late night salivary cortisol test suggest?

A

Normally, cortisol levels drop after we fall asleep.
However, if the cortisol levels don’t drop, it suggests Cushing’s syndrome.

60
Q

What is the 24 hour urinary free-cortisol test?
(test to see for Cushing’s syndrome)

A

This is where urine of the patient is collected over a 24 hour period

61
Q

What do the results of the 24 hour urinary test suggest?

A

If the patient has higher than normal levels of cortisol in their urine, it suggests Cushing’s syndrome.
Levels higher than 50-100 micrograms per day in an adult suggest Cushing’s syndrome.

62
Q

When carrying out a blood test to check the amount of ACTH levels in a patient, what would be the cause of low ACTH levels?

A

The cause is likely to be a tumour in the adrenal glands.

63
Q

When carrying out a blood test to check the amount of ACTH levels in a patient, what would be the cause of normal/high ACTH levels?

A

The cause is likely to be a pituitary tumour or an ectopic tumour

64
Q

What is the CRH simulation test?
And how does it test to see whether a pituitary tumour is present?

A

If a tumour is present, CRH will increase the levels of ACTH and cortisol in the blood.

65
Q

How does the HIGH dose dexamethasone suppression test (HDDST) test to see whether you have a pituitary tumour?

A

If after taking a high dose of dexamethasone, your cortisol levels in your blood drop, then you probably have a pituitary tumour.

66
Q

How can imaging tests check for pituitary and adrenal tumours?

A

They show the size/shape of the pituitary and adrenal glands to look for tumours.

The most common imaging tests are computerised photography (CT)
and magnetic resonance imaging(MRI)

67
Q

How can you treat Cushing’s syndrome?

A

Drugs directed at the pituitary

Drugs directed at the adrenal glands.

Drugs directed at glucocorticoid receptors

68
Q

What do drugs directed at the pituitary do to treat Cushing’s syndrome/

A

They decrease ACTH production.

E.G. Pasireotide, Cabergoline

69
Q

What do drugs directed at the adrenal glands do to treat Cushing’s syndrome do?

A

They try to control excess production of cortisol at the adrenal glands.

E.G. Steroidogenesis inhibitors, Milotane(adsrenolytic drug)

70
Q

What do drugs directed at glucocorticoid receptors to treat Cushing’s syndrome do?

A

It doesn’t decrease cortisol production, but blocks the effect of cortisol on your tissues.

E.G. Mifepristone

Physiology & metabolism (8 decks)

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