Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Endocrinology > Hyper/hypothyroidism > Flashcards

Hyper/hypothyroidism Flashcards

1
Q

What are the 4 major histological components of the thyroid gland?

A

Follicle - secretory sac containing colloid
Colloid - mixture which contains prohormone thyroglobulin
Follicular cells - cells which make up the follicle
Parafollicular cells (C-cells) - calcitonin secreting cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Describe the steps in the formation of thyroid hormone.

A
  1. Iodine taken up by follicular cells and passed into colloid.
  2. Iodine attaches to thryoglobulin forming either monoiodotyrosine (MIT) ot di-iodotyrosine (DIT)
  3. MIT+DIT = triiodothyronine (T3)
    DID+DID = thyroxine (T4)
  4. T3 and T4 stored in colloid
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Describe the steps in the secretion of thyroid hormone.

A
  1. Thyroid releasing hormone (TRH) secreted from hypothalamus and acts on anterior pituitary gland to release thyroid stimulating hormone (TSH).
  2. TSH acts on G-protein coupled receptors on follicular cells which increases intracellular cAMP
  3. Stimulates transportation of T3/T4 into follicular cells by and then into the blood by pinocytosis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the active form of thyroid hormone?

A

T3 (triiodothyronine)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What transports thyroid hormone in the blood?

A

Thyroxine binding protein (70%)

Also transthyretin (20%) and albumin (5%)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Describe the steps in the action of thyroid hormone.

A
  1. T3/T4 enters cell through membrane transporter and T4 converted to T3 by de-iodinase 2 (D2) enzymes in cytoplasm
  2. T3 binds to and activates thyroid hormone receptor in the nucleus
  3. This converts inhibitoary co-repressor (CoR) to co-actuivator (CoA) protein which binds to thyroid response element (TRE) on DNA increasing metabolic rate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What enzyme converts T4 to T3 inside tissues?

A

Deiodinase 2 (D2)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is hyperthyroidism?
What is thyrotoxicosis?

Why are they different?

A

Hyperthyroisism - overactive thyroid gland

Thyrotoxicosis - state arising when tissues exposed to excess thyroid hormone

Thyrotoxicosis can occur without hyperthyroidism e.g. excess exogenous thyroxine, ectopic thyroid tissue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is primary hyperthyroidism?

A

Problem within the thyroid gland causing hypersecretion.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

TFTs show:

  • T3/4: high
  • TSH: low

Diagnosis?

What test would you do next and why?

A

Primary hyperthyroidism

TSH receptor antibody (TRAb): helps differentiate Graves’ disease from mutinodular goitre/solitary toxic nodule

TRAb elevated - Graves

TRAb low - not Graves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is Graves’ disease?

A

Autoimmune condition of the thyroid gland (thyroid receptor antibody - TRAb) causing hyperthyroidism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How does Graves’ disease present?

A 
Tachycardia, anxiety, sweating, tremor
Muscle weakness
Weight loss and increased appetite
Diarrhoea
Light periods/amenorrhoea

Proptosis

Smooth goitre

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is pretibial myxoedema?

A

Swelling and lumpiness of shins from Graves’ disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is Thyroid Eye Disease (TED)?

A

Exopthalmus, lid retraction and painful eye movements caused by Graves’ disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Are thyroid cancers normally

  • hyperthyroid
  • euthyroid
  • hypothyroid?
A

Usually euthyroid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is choriocarcinoma and why can it cause hyperthyroidism?

A

Tumour secreting human chorionic gonadotrophin (hCG)

Has a very similar structure to TSH (alpha chains identical, ß chain different) and can mimic its effects

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What does amiodarone do to T3/4 levels and why?

What is the clinical significange of this?

A

Amiodarone inhibits deiodinase 1 (DIO1) which converts T4 to T3 resulting in high T4 and low T3

This tends to cause

  • hyperthyroidism in iodine deficient areas
  • hypothyroidism in iodine rich areas
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

TFTs show:

  • T3/4: high
  • TSH: high

Diagnosis?

A

Secondary hyperthyroidism

Dysfunctional hypothalamic-pituitary-thyroid axis producing excess TSH and consequent T3/4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

TFTs show:

  • T3/4: normal
  • TSH: low

Diagnosis?

A

Subclinical hyperthyroidism

Biological state which has risk of progressing to overt hyperthyoidism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How is hyperthyroidism treated?

A

Anti-thyroid drugs (carbimazole, propylthiouriacil)

ß-blockers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Patient in first trimester of pregnancy is diagnosed with hyperthyroidism. What treatment do you prescribe?

A

Propylthiouracil

22
Q

Name 2 anti-thyroid drugs and their different characteristics.

A

Carbimazole

  • first line
  • once daily
  • less side effects
  • more potent

Propylthiouracil

  • second line (unless 1st trimester of pregnancy)
  • twice daily
  • more side effects
  • less potent
23
Q

What is the most important side effect to warn patients on anti-thyroid drugs (ATD) about?

A

Agranulocytosis

(warn patient verbally and in writing that if they get fever they must stop drugs and get urgent FBC)

Patient can never use ATD again.

24
Q

How do you manage a patient with hyperthyroidism who developed agranulocytosis after using antithyroid medication?

A

Radioiodine

Thyroidectomy if radioiodine contraindicated (pregnancy, active thyroid eye disease)

25
Q

What is the main risk in thyroidectomy?

A

Recurrent laryngeal nerve palsy

26
Q

What is a thyroid storm?

A

Acute and serious attack of hyperthyroidism usually affecting hyperthyroid patient who suffers acute infection/surgery

27
Q

How do you manage thyroid storms?

A

ABC
High dose antithyroid drugs
Hydrocortisole
Potassium iodide

28
Q

TFTs show:

  • T3/4: low
  • TSH: high

Diagnosis?

What test would you do next and why?

A

Primary hypothyroidism

Anti-thyroid peroxidase (anti-TPO)

Would be raised in Hashimoto’s thyroiditis

29
Q

How does Hashimoto’s thyroiditis present?

A

Weight gain, lethargy, puffy skin, bradycardia, consipation
Menorrhagia/amenorrhoea
Slow tendon jerks

Goitre

30
Q

Why does hypothyroidism cause oligo/amenorrhoea?

A

Increased TRH increases prolactin secretion. Prolactin inhibits gonadotrophin action

31
Q

What treatments can cause hypothyroidism?

A

Radiotherapy
Amiodarone
Lithium
Thyroidectomy

32
Q

What is the commonest cause of hypothyroidism

  1. in the UK
  2. worldwide?
A
  1. Hashimoto’s thyroiditis

2. Iodine deficiency

33
Q

TFTs show:

  • T3/4: low
  • TSH: low

Diagnosis?

A

Secondary hypothyroidism

Dysfunctional hypothalamic-pituitary-thyroid axis

34
Q

TFTs show:

  • T3/4: normal
  • TSH: high

Diagnosis?

A

Subclinical hypothyroidism

35
Q

What does hypothyroidism cause in babies? Why is this rare?

A

Cretinism: dwarfism and poor mental function (thyroid hormones important in brain development)

Guthrie screening test (5th day of life TFTs done) means this is rare

36
Q

How do you treat primary hypothyroidism?

A

Slowly increase thyroid levels with daily levothyroxine (T4 tablets)

37
Q

What doses of levothyroxine are used in

  1. normal patients?
  2. elderly?
  3. pregnant women?
A
  1. 50-100µg
  2. 25-50µg (half)
  3. Increase previous dose by 25µ
38
Q

What is myxoedema coma?

A

Potentially fatal loss of brain function from severe hypothyroidism

39
Q

How does myxoedema coma present?

A

Hypothyorid signs

Reduced mental status

Hypothermia

Respiratory failure

40
Q

How do you manage myxoedema coma?

A 
ABC
Slowly rewarm
Broad spectrum antibiotics
Cautious thyroxine
Hydrocortisone if adrenal failure
41
Q

What is sick euthyroid syndrome?

A

Abnormal TFTs caused by non-thyroid illness

Avoid checking TFT in ill patient without clinical indication of thyroid pathology

42
Q

What TFT pattern often shows in ill people?

A

Sick euthyroid syndrome

  • T3/4: low
  • TSH: low
43
Q

How would resistance to thyroid receptor hormone alpha (TRa1/2 mutation) present?

A

Delayed development
Bradycardia
Chronic consiptation

44
Q

How would resistance to thyroid receptor hormone beta (TRß1/2 mutation) present?

A

Increased T3/4 and TSH
Goitre
Affected colour vision

45
Q

Is resistance to thyroid receptor alpha or beta more common?

A

resistance to thyroid receptor hormone beta is more common

46
Q

What does thyroiditis show on scintigraphy?

A

Homogenously reduced iodine uptake

47
Q

What is the classic effect of thyroidtitis on thyroid hormone levels?

A

Increased initially
Hypothyroid after
Euthyroid once inflammation settles

48
Q

Name 3 causes of thyroiditis and when they would present.

A

De Quervian’s thyroiditis - after viral infection

Post-partum thyroiditis - after pregnancy

Drug induced thyroiditis - after treatment with amiodarone/lithium

49
Q

What TFT pattern do multinodular goitres often show?

A

Subclinical hyperthyroidism
(normal T3/4, low TSH)

This can progress to primary hyperthyroidism (high T3/4, low TSH)

50
Q

What investigations can be done if patient presents with breathlessness and a multinodular goitre?

A

CT scan

Flow volume loops

51
Q

What does a multinodular goitre often show on scintigraphy?

A

Multiple nodules but one dominant nodule taking up most of the iodine

52
Q

When is surgery indicated in toxic multinodular goitre?

A

Tracheal compression
Retrosternal extension
Cancer suspicion

Endocrinology (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions