Thyrotoxicosis

Question 1

What is thyroitoxicosis?

Answer 1

Thyrotoxicosis is the state produced by excessive thyroid hormone. It is not strictly the same thing as hyperthyroidism, as thyrotoxicosis can exist without hyperthyroidism being present – for example – after the administration of excessive thyroxine that may be seen when hypothyroidism is treated. However, in clinical practice, the terms thyrotoxicosis and hyperthyroidism are often used interchangeably.

Question 2

What is the prevalence of thyrotoxicosis in GP practice?

Answer 2

Thyrotoxicosis is a common GP presentation – with a prevalence of around 0.5%

Question 3

What is the most common cause of Thyrotoxicosis?

Answer 3

Grave’s disease

Question 4

What are other causes of thyrotoxicosis?

Answer 4

1. Toxic multinodular goitre
2. Toxic adenoma
3. Thyroiditis
4. Occasionally, Hashimoto’s disease

Question 5

What is the epidemiology of Thyrotoxicosis?

Answer 5

Affects 2-5% of females and 0.2-03% of men.
The female : male ratio is 5:1.
Onset usually occurs between the ages of 20 and 40 in cases of Graves disease, but later in life where the cause is nodular thyroid disease.
99% of cases are caused by intrinsic thyroid disease, and less than 1% caused by a primary pituitary problem.
Grave’s disease accounts for 60-80% of cases of thyrotoxicosis.
Nodular thyroid disease accounts for most of the rest (20-40%).

Question 6

What is Grave’s disease?

Answer 6

Grave’s disease is an autoimmune disorder caused by the production of TSH receptor stimulating antibodies.
These antibodies stimulate the thyroid gland to produce more T3 and T4

Question 7

What is hyperthyroidism?

Answer 7

over-production of thyroid hormones T3 and T4

Question 8

What is primary hyperthyroidism?

Answer 8

where the thyroid gland produces excessive thyroid hormones

Question 9

What is secondary hyperthyroidism?

Answer 9

where pathology in the hypothalamus or pituitary produces too much TSH, stimulating the thyroid gland to produce excessive thyroid hormones

Question 10

How do thyroid hormones influence the basal metabolic rate?

Answer 10

by controlling the rate of cellular oxidative phosphorylation

Question 11

What autoantibodies are associated with Grave’s disease?

Answer 11

anti-TSH receptor autoantibodies

Question 12

Describe the pathophysiology of Grave’s disease:

Answer 12

autoantibodies bind to TSH receptors on the thyroid gland and stimulate increased production of T3 and T4

Question 13

What is Plummer’s disease also known as?

Answer 13

toxic multinodular goitre

Question 14

What is toxic multinodular goitre?

Answer 14

where nodules develop on the thyroid gland which are unregulated by the thyroid axis and continuously produce excessive T3 and T4

Question 15

Give 6 causes of thyrotoxicosis:

Answer 15

1) Grave’s disease
2) toxic multinodular goitre
3) iodine excess
4) solitary toxic thyroid nodule
5) thyroiditis
6) drugs (amiodarone and levothyroxine)

Question 16

What is a solitary toxic thyroid nodule?

Answer 16

where a single abnormal thyroid nodule (often benign adenomas) acts along to release excessive thyroid hormone

Question 17

Give 3 types of thyroiditis that can cause thyrotoxicosis:

Answer 17

1) post-partum thyroiditis
2) Hashimoto’s thyroiditis
3) De Quervain’s thyroiditis

Question 18

What is De Quervain’s thyroiditis?

Answer 18

where a viral infection causes inflammation that stimulates a sudden rise in thyroid hormone which presents as a painful lump in the neck which later becomes hypothyroidism

Question 19

Name two drugs that can cause thyrotoxicosis:

Answer 19

1) amiodarone (contains iodine)
2) levothyroxine

Question 20

Give 10 clinical presentations associated with thyrotoxicosis:

Answer 20

1) anxiety and irritability
2) sweating and heat intolerance
3) tachycardia and palpitations
4) weight loss
5) fatigue
6) insomnia
7) diarrhoea
8) sexual dysfunction and reduced libido
9) brisk reflexes
10) tremor

Question 21

What is a thyrotoxic storm?

Answer 21

Thyrotoxic storm is severe acute presentation of thyrotoxicosis (thyrotoxic crisis). In a similar way to myxedema coma, this often presents as a result of acute illness, and there may not be any previous history of thyrotoxicosis. It has a 20-30% mortality rate.

Question 22

What are the clinical presentations of a thyrotoxic storm?

Answer 22

A marked fever (>38.5’)
Seizures
Vomiting
Diarrhoea
Jaundice
Death – can be caused by arrhythmias, heart failure or hyperthermia.

Question 23

What is the treatment for a thyrotoxic storm?

Answer 23

Treatment should be started as soon as possible – and patients should be given propanolol, antithyroid drugs, potassium iodide (to reduce vascular flow to the gland) and corticosteroids.

Question 24

Give 4 clinical presentations specific to Grave’s disease:

Answer 24

1) diffuse goitre (no nodules)
2) Grave’s eye disease (exophthalmos)
3) pretibial myxoedema
4) thyroid acropachy (hand swelling and clubbing)

Question 25

What is pretibial myxoedema?

Answer 25

a skin condition where deposits of glycosaminoglycans build up under the skin of the anterior aspect of the leg giving the skin a discoloured, waxy and oedematous appearance

Question 26

Describe the T3, T4 and TSH results expected in primary hyperthyroidism:

Answer 26

high T3 and T4, low TSH (negative feedback)

Question 27

Describe the T3, T4 and TSH results expected in secondary hyperthyroidism:

Answer 27

high T3 and T4 and high TSH

Question 28

What three antibodies are associated with hyperthyroidism?

Answer 28

1) anti-TSHR
2) anti-thyroid peroxidase (also associated with hypothyroidism)
3) anti-thyroglobulin (also associated with hypothyroidism)

Question 29

What imaging should be used to investigate every thyroid lump?

Answer 29

ultrasound

Question 30

What is radionulide scans used for?

Answer 30

is the imaging modality of choice in differentiating the cause of thyroxtoxicosis

Question 31

What is the main nuclide used for a radionuclide scan?

Answer 31

Technithium pertechnetate (Tc-99m)

Question 32

What results would be shown on a radionuclide scan for different causes of thyrotoxicosis?

Answer 32

Grave’s disease – diffuse widespread uptake
Toxic multinodular goitre – Can be normal, or may show multiple nodes of uptake, with the rest of the thyroid often showing reduced uptake
Toxic adenoma – single area of increased uptake
Thyroiditis – none or minimal uptake

Question 33

what is the first line treatment for thyrotoxicosis/ Graves disease?

Answer 33

Anti-thyroid drug

Question 34

What is the first-line anti-thyroid drug?

Answer 34

carbimazole

Question 35

Describe the two ways in which carbimazole can be used to treat hyperthyroidism:

Answer 35

1) titration block - carbimazole titrated to keep T3 and T4 at a euthyroid level
2) block and replace - carbimazole is given at high doses to stop T3 and T4 production and levothyroxine is given as a replacement

Question 36

What is the second line anti-thyroid drug?

Answer 36

propylthiouracil

Question 37

What is a key side effect of carbimazole and propylthiouracil?

Answer 37

agranulocytosis and low WBC count (increased susceptibility to infection)

Question 38

Why are beta blockers prescribed as well as anti-thyroid drugs?

Answer 38

These are often used immediately after diagnosis to control the symptoms, before the drugs that affect thyroid hormones have taken effect.
They will reduce symptoms such as:
Tachycardia
Dysrhythmias
Tremor
Agitation
Beta-blockers also decrease peripheral conversion of T4 to T3.
In cases where beta-blockers are contraindicated (e.g. in asthma), then calcium channel blockers can be considered

Question 39

What beta blocker is commonly used in hyperthyroid treatment?

Answer 39

propanol

Question 40

Describe radioiodine as a treatment for hyperthyroidism:

Answer 40

patient drinks a single dose of radioactive iodine which the thyroid takes up - the radiation destroys a portion of the thyroid, reduces T3 and T4 production

Question 41

Name the 3 conditions for the use of radioiodine as a treatment for hyperthyroidism:

Answer 41

1) women must not be pregnant or breast feeding or get pregnant within 6 months of treatment
2) men must not father children within 4 months of treatment
3) limit contact with people after the dose - particularly children and pregnant women

Question 42

Give 3 instances where a thyroidectomy would be indicated to treat thyrotoxicosis:

Answer 42

1) other treatments are unsuccessful or unsuitable
2) thyroid goitre is causing compression to surrounding structures
3) thyroid malignancy is suspected

Question 43

What drug has to be taken lifelong after a thyroidectomy?

Answer 43

levothyroxine

Question 44

What is the long-term risk of hyperthyroidism?

Answer 44

increased risk of osteoporosis