Thyroid

Question 1

Recall the physiology of the thyroid gland

Answer 1

TSH causes an uptake of iodide, and thyroid peroxidase turns iodide into iodine. TSH then binds iodine to thyroglobulins to form thyroxine, and thyroxine is released.

Question 2

How is the hypothalamus and the pituitary associated with the thyroid?

Answer 2

The hypothalamus releases TRH, which acts on the pituitary. The pituitary releases TSH which acts on the thyroid. T4 give negative feedback to the hypothalamus and the pituitary.

Question 3

What is hypothyroidism?

Answer 3

A lack of thyroxine, underactive thyroid

Question 4

What are the clinical features of hypothyroidism?

Answer 4

• Reduced basal metabolic rate (weight gain)
• Cold hands
• Constipation
• Dysmenorrhoea and infertility

Question 5

How should you investigate hypothyroidism?

Answer 5

• Blood TSH and T4

- Other autoimmune conditions

Question 6

What are the causes of hypothyroidism?

Answer 6

Autoimmune

• Hashimoto’s Thyroiditis (anti-thyroid peroxidase autoantibodies)
• Primary atrophic hypothyroidism

Other

• Iodine deficiency
• Post thyroidectomy/radioiodine
• Drug induces (amiodarone, lithium)

Question 7

What is subclinical hypothyroidism? What is this associated with?

Answer 7

A high TSH with a normal T4

This is associated with hypercholesterolaemia

Question 8

How do you manage hypothyroidism?

Answer 8

Check ECG to rule out CVD

Thyroxine replacement (levothyroxine) depending on BMI

50/125/200 mcg a day

Question 9

What is hyperthyroidism?

Answer 9

An overactive thyroid

Question 10

What can cause hyperthyroidism?

Answer 10

High uptake

• Grave’s disease (TSH receptor autoantibodies)
• Toxic multinodular goitre
• Toxic adenoma

Low uptake

• De Quervain’s thyroiditis
• Postpartum thyroiditis

Question 11

What are the features of hyperthyroidism?

Answer 11

• Increase basal metabolic rate (weight loss)
• Palpitations, AF
• Diarrhoea
• Dysmenorrhea and infertility

If Graves:

• Exophthalmos
• Smooth goitre

Question 12

How do you investigate a case of hyperthyroidism?

Answer 12

• TSH
• Free T4
• Other autoimmune diseases

Question 13

What is the management of hyperthyroidism?

Answer 13

• Beta blockers for heart rate
• Radioiodine
• Carbimazole (if unresponsive to radioiodine)
• Thyroidectomy (then thyroxine replacement)

Question 14

What is the most common thyroid neoplasia? What is the epidemiology surrounding it, how do you treat it and what is the prognosis?

Answer 14

Papillary (60%) of cases., usually in ages 30-40. It is treated with surgery, and carries an excellent prognosis.

Question 15

What are the thyroid neoplasia, in order of most common.

Answer 15

• Papillary (60%)
• Follicular (25%)
• Medullary
• Lymphoma
• Anaplastic

Question 16

Describe follicular thyroid cancer

Answer 16

Usually middle aged, well differentiated and surgery is used to treat

Question 17

Describe medullary thyroid cancer

Answer 17

Originates in the parafollicular C cells
Either:
- Linked to MEN2
- Familial

Question 18

Describe thyroid lymphoma

Answer 18

5% of all thyroid cancer cases, and has a MALT origin. Is precipitated by long standing Hashimoto’s disease

Question 19

Describe anaplastic thyroid cancer

Answer 19

Usually affects the elderly and is generally unresponsive to treatment; poor prognosis

Question 20

How can you investigate thyroid cancer?

Answer 20

Thyroglobulin is a marker of cancer cells

• Use to confirm diagnosis
• Use to confirm remission

Question 21

What is subclinical hyperthyroidism?

Answer 21

Where the T4 is normal but the TSH is low. This may progress to primary hypothyroidism.