L7 Thyroid Hormones 2

Question 1

Toxic multinodular goitre usually occurs in…

Answer 1

older patients with longstanding euthyroid multinodular goitre

Question 2

Presentations of toxic multinodular goitre

Answer 2

• tachycardia, heart failure or arrhythmia
• sometimes weight loss, nervousness, weakness, tremors & sweats

Question 3

Laboratory findings of toxic multinodular goitre

Answer 3

suppressed TSH, elevated serum T3 levels, less striking elevation of serum T4

Question 4

Toxic multinodular goitre management

Answer 4

• control of the hyperthyroid state with anti-thyroid drugs, followed by radioiodine (therapy of choice)
• if goitre is very large, thyroidectomy is considered if patient is a good surgical candidate

Question 5

What is amiodarone?

Answer 5

an anti-arrhythmic drug that contains 37.3% iodine by weight

Question 6

Two types of amiodarone-induced thryotoxicosis

Answer 6

Type 1: thyrotoxicosis due to excess iodine
Type 2: amiodarone-induced thyroiditis, with inflammation and release of stored hormone into the bloodstream, causing thyrotoxicosis

Question 7

Which type of AIT typically develops after more prolonged amiodarone use?

Answer 7

Type 2 - thyroiditis

Question 8

Treatment for AIT

Answer 8

• iodine-induced thyrotoxicosis can be controlled with methimazole/carbimazole and beta blockers
• treatment with potassium perchlorate to block further iodine uptake requires careful monitoring because it has been associated with pernicious anaemia
• prednisone therapy for drug-induced thyroiditis
• mixed form of disease is treated with both thioamides and prednisone
• total thyroidectomy is curative - may be needed in patients who are non-responsive to pharmacologic therapy

Question 9

What is non-toxic goitre?

Answer 9

Goitre not associated with hyperthyroidism, can be diffuse or nodular

Question 10

What is the most common cause of non-toxic goitre?

Answer 10

Iodine deficiency

Question 11

Development of NTG in patients with impaired hormone synthesis or severe iodine deficiency causes an increase in __ secretion.

Answer 11

TSH

Question 12

TSH-induced diffuse thyroid hyperplasia causes…

Answer 12

focal hyperplasia with necrosis and haemorrhage, and development of new areas of focal hyperplasia

Question 13

Focal or nodular hyperplasia may or may not be able to…

Answer 13

concentrate iodine or synthesise TG

Question 14

Initially, the hyperplasia is dependent upon…

Answer 14

TSH, but later the nodules become TSH-independent

Question 15

Mutations of which gene have been found in a high proportion of nodules from patients with multinodular goitre?

Answer 15

gsp oncogene

Question 16

Chronic activation of which protein results in thyroid cell proliferation and hyperfunction, even when TSH is suppressed?

Answer 16

the Gs protein

Question 17

Patients with NTG usually present with?

Answer 17

thyroid enlargement, may be diffuse or multinodular

Question 18

What indicates obstruction to jugular venous flow?

Answer 18

Positive Pemberton sign: facial flushing and dilation of cervical veins on lifting the arms over the head

Question 19

The vast majority of patients with NTG are __.

Answer 19

euthyroid

Question 20

Thyroid enlargement in NTG probably represents __ __.

Answer 20

compensated hypothyroidism

Question 21

NTG treatment

Answer 21

• with the exception of those due to neoplasm, the current management of NTG consists simply of observation, without any specific therapy
• thyroid hormone suppression therapy rarely results in clinically significant decrements in goitre size
• T4 therapy may be required to suppress serum TSH levels (but could cause harm to elderly patients)

Question 22

TSH-independent/autonomous NTGs will not decrease in size and may contribute to…

Answer 22

iatrogenic hyperthyroidism

Question 23

Subacute thyroiditis is also known as…

Answer 23

De Quervain thyroiditis or granulomatous thyroiditis

Question 24

What is subacute thyroiditis?

Answer 24

An acute inflammatory disorder of the thyroid gland, most likely due to viral infection

Question 25

Examples of viruses that have been implicated in subacute thyroiditis

Answer 25

- mumps virus - coxsackievirus - adenoviruses

Question 26

Histological features of subacute thyroiditis

Answer 26

destruction of thyroid parenchyma, presence of many phagocytic cells (including giant cells)

Question 27

Who is more susceptible to subacute thyroiditis?

Answer 27

women, and individuals who are HLA-Bw35 positive

Question 28

Signs & symptoms of subacute thyroiditis

Answer 28

- fever, malaise, soreness in the anterior neck - initially, patient may have symptoms of hyperthyroidism, with palpitations, nervousness & sweats - clinical signs of thyrotoxicosis (tachycardia, tremor, hyperreflexia) may be present

Question 29

Treatment of subacute thyroiditis

Answer 29

- NSAIDs - patients who do not respond to NSAIDs - glucocorticoid treatment e.g. prednisone (daily for 7-10 days) to reduce inflammation - beta blockers to treat hyperthyroid symptoms - T4 if hypothyroid symptoms are present. T4 therapy may also prevent exacerbations of inflammation due to elevated TSH levels

Question 30

Chronic thyroiditis is also known as...

Answer 30

Hashimoto's disease/thyroiditis or lymphocytic thyroiditis

Question 31

What is the most common cause of hypothyroidism and goitre in the US?

Answer 31

Hashimoto's disease

Question 32

Example of an end stage of Hashimoto thyroiditis?

Answer 32

Idiopathic myxoedema, with total destruction of the gland

Question 33

Most common signs/symptoms of Hashimoto thyroiditis

Answer 33

- fatigue & sluggishness - increased sensitivity to cold - unexplained weight gain - enlarged & inflamed underactive thyroid (goitre)

Question 34

What is Hashimoto's disease?

Answer 34

An immunologic disorder in which lymphocytes become sensitised to thyroidal antigens and auto-antibodies are formed that react with these antigens. The thyroid gland is gradually destroyed.

Question 35

The 3 most important thyroid auto-antibodies

Answer 35

TG Ab, TPO Ab, TSH-R-blocking Ab

Question 36

Which auto-antibody is be present for many years?

Answer 36

TPO Ab

Question 37

What are Hurthle cells?

Answer 37

In Hashimoto thyroiditis, the follicular epithelial cells of the thyroid gland are frequently enlarged and contain an eosinophilic cytoplasm laden with mitochondria. These are known as Hurthle cells.

Question 38

What happens following destruction of the thyroid gland in Hashimoto thyroiditis?

Answer 38

a fall in serum T3 and FT4 and a rise in TSH

Question 39

What is Schmidt syndrome?

Answer 39

consists of Hashimoto thyroiditis, idiopathic adrenal insufficiency, and commonly, T1DM. The phenomenon has also been called the autoimmune polyglandular syndrome.

Question 40

Indications for Hashimoto's disease treatment

Answer 40

goitre or overt hypothyroidism (symptoms are usually mild)

Question 41

When is surgery considered for Hashimoto thyroiditis?

Answer 41

Rarely, but occasionally when goitre does not regress and continues to cause compressive symptoms

Question 42

Dyslipidaemia associated with Hashimoto's disease can be ameliorated by...

Answer 42

T4 therapy

Question 43

What is administered to normalise TSH and allow regression of the goitre in Hashimoto's disease?

Answer 43

sufficient T4

Question 44

Agenesis of one lobe of the thyroid, with hypertrophy of the other, can produce benign thyroid nodules. Which lobe is more likely to fail to develop?

Answer 44

It is usually the left lobe of the thyroid that fails to develop, and the hypertrophy occurs in the right lobe (presents as a mass in the neck and mimics a nodule)

Question 45

Examples of benign areas of hyperplasia and neoplasms in the thyroid that present as thyroid nodules

Answer 45

follicular adenomas, and Hurthle cell adenomas (also called oxyphil adenomas)

Question 46

Examples of rare benign thyroidal lesions

Answer 46

teratomas, lipomas, haemangiomas

Question 47

Diagnosis of a thyroid nodule

Answer 47

A patient with a thyroid nodule should have a serum TSH and thyroid ultrasound performed. If TSH is low, radionuclide thyroid scanning should be done.

Question 48

What happens when a nodule is cytologically malignant?

Answer 48

the patient is generally referred for thyroid surgery

Question 49

What happens when the nodule is classified as cytologically benign?

Answer 49

only reassessment of nodule size in 6-18 months by physical examination and/or ultrasound is required

Question 50

Types of thyroid cancer

Answer 50

- papillary carcinoma (80%) - follicular carcinoma (10%) - medullary carcinoma (5%) - undifferentiated (anaplastic) carcinomas (3%) - miscellaneous e.g. lymphoma, teratoma, fibrosarcoma (1%)

Question 51

Most common type of thyroid cancer

Answer 51

papillary carcinoma

Question 52

Management of thyroid cancer (low risk patients)

Answer 52

- Lobectomy or total thyroidectomy - radioiodine not given to most low risk patients - thyroxine for life with maintenance of low normal serum TSH - monitor with serum TG and neck ultrasound every 6-12 mnths for first 1-5 yrs

Question 53

Management of thyroid cancer (high risk patients)

Answer 53

- surgery - radioiodine therapy given to most intermediate and all high risk patients - thyroxine for life with maintenance of suppressed serum TSH - monitor with serum TG and neck US every 6-12 mnths for 3-5 yrs - repeat radioiodine scan and measure serum stimulated thyroglobulin