Hyperthyroidism

Question 1

What is the most common for of hyperthyroidism in most areas of the world?

Answer 1

Grave’s disease

Autoimmune thyroid disease

Caused by stimulatory TSH receptor antibodies (TRAb)

Question 2

Causes of hyperthyroidism

Answer 2

• Grave’s
• Pituitary adenoma
• Levothyroxine
• Iodine
• Amiodarone
• Toxic thyroid adenoma
• Toxic multinodular goitre

Question 3

Thyroid axis

Answer 3

Hypothalamus secretes TRH - thyrotropin releasing hormone

Anterior pituitary secretes TSH

TSH binds to receptors on the thyroid and causes it to release T3 and T4 into the blood

T3 and T4 then inhibit the production of TRH and TSH

Question 4

Pathophysiology of Grave’s disease

Answer 4

Autoantibodies (TRAbs) bind to the TSH receptor on the thyroid gland and cause the gland to release thyroid hormones

The high levels of T3 and T4 feedback to the anterior pituitary to tell it to stop producing TSH

Question 5

How do patients with hyperthyroidism present?

Answer 5

As if everything is sped up/ buzzing

• Hyperactive
• Fast speech
• Tremor in extremities
• Sweaty
• Anxiety
• Irritability

THINK TOOOOO MUCH COFFEE ☕️

Question 6

What is the overall function of thyroid hormones?

Answer 6

Increase the rate of metabolism within cells

• Increase rate of thinking, moving and talking
• Increase heat generation
• Activate the sympathetic nervous system

Question 7

Physical examination in a patient with hyperthyroidism

Answer 7

Skin: warm and moist

Hair: fine and brittle

• Eyelid retraction
• Pretibial myxoedema
• Muscle weakness
• Exagerated deep tendon reflexes
• Tachycardia
• Mesntrual irregularities

Question 8

1st investigations for hyperthyroidism

Answer 8

• TSH - if normal it is unlikely the patient has hyperthyroidism
• Serum free or total T3 and T4: elevated

Low TSH and normal T3/T4 - subclinical hyperthyroidism

Low TSH and raised T3/T4 = hyperthyroidism

Question 9

Thyroid function tests in pregnancy

Answer 9

Physiological suppression of TSH levels can occur in the first trimester of pregnancy due to the stimulation of thyroid hormone release by hCG = GESTATIONAL TRANSIENT THYROTOXICOSIS

T4 levels usually normalise by week 14-18

Question 10

Secondary tests to consider in the case of hyperthyroidism

Answer 10

• Blood test for TRAbs - will be + if Grave’s disease is the cause
• Thyroid USS
• CT or MRI of orbit
• Radioactive iodine uptake - if the patient has Grave’s their uptake level will be higher

Question 11

What is the second most common cause of hyperthyroidism?

Answer 11

Toxic multinodular goitre

At least two autonomously functioning thyroid nodules secrete excess thyroid hormone

Question 12

What is a thyroid storm?

Answer 12

Life-threatening condition associated with untreated hyperthyroidism

Results in volume depleteion, vomiting, agitation, increased heart rate and blood pressure and rising body temperature

Question 13

How is a thyroid storm managed?

Answer 13

High dose anti-thyroid medication

Propylthiouracil, carbimazole, thiamazole

Corticosteroids, beta blockers, iodine solution and supportive care

Question 14

What are the results of TFTs in the case of thyroid cancer?

Answer 14

Usually normal

Question 15

Discuss medication for hyperthyroidism

Answer 15

Should only be initiated following advice from speciliast and are typically used short term to restore euthyroidism, medium term to induce remission in Grave’s or long term if radioactive iodine treatment or surgery is contraindicated or declined

Carbimazole and propythiouracil

*propythiouracil is usually not used first line because it can cause liver injury*

Question 16

How long does it generally take for people to become euthyroid after treatment with carbimazole?

Answer 16

4-8 weeks

Question 17

Once the patient is euthyroid, how is hyperthyroidism managed?

Answer 17

a) Titration block regime: dose of carbimazole is adjusted based on T4 levels with the aim being to titrate to the lowest dose needed to maintain euthyroidism
b) Block and replace regime: carbimazole given to suppress thyroid hormone synthesis until it is within the reference range and then levothyroxine given - continued for 18months

Question 18

Discuss radioactive iodine treatment

Answer 18

First line - definitive treatment for adults with Grave’s disease and those with toxic multinodular goitre

Radioactive iodine induces damage and death of thyroid cells

Most people become euthyroid and then hypothyroid 6weeks - 6months after treatment

*Contraindicated in women who are pregnant or planning pregnancy within 4-6 months as it crosses the placenta*

Question 19

Typical presentation of thyroid cancer

Answer 19

Asymptomatic thyroid nodule in a woman in her 30s/40s

Detected following physical examination or an incidental finding on neck USS/ CT