Thyroid Disease

Question 1

Describe the thyroid axis

Answer 1

Hypothalamus secretes TRH (thyrotropin-releasing hormone) which stimulates TSH (thyroid-stimulating hormone) from anterior pituitary. TSH increases production of T3 and T4 from thyroid gland. T3 and T4 have a negative feedback effect on production of TSH.

Question 2

What would you expect the thyroid function tests of a patient with primary hypothyroidism to show?

Answer 2

Low T4

High TSH

Question 3

What are the causes of primary hypothyroidism?

Answer 3

Hashimoto’s thyroiditis (an autoimmune condition)
Post-treatment e.g. surgery, anti-thyroid medication, radioactive iodine
Primary atrophic hypothyroidism

Question 4

What would you expect the thyroid function tests of a patient with primary hyperthyroidism to show?

Answer 4

Low TSH

High T4

Question 5

What are the causes of primary hyperthyroidism?

Answer 5

Grave’s disease
Toxic multinodular goitre
Solitary toxic adenoma

Question 6

What would you expect the thyroid function tests of a patient with secondary hypothyroidism to show?

Answer 6

TSH normal or borderline low (definitely not raised)

T4 low

Question 7

What would you expect the thyroid function tests of a patient with secondary hyperthyroidism to show?

Answer 7

Borderline high TSH

High T4

Question 8

What are the causes of secondary hyperthyroidism?

Answer 8

TSHoma - a TSH secreting tumour

Question 9

What are the causes of secondary hypothyroidism?

Answer 9

Pituitary / hypothalamic dysfunction

Question 10

What is the most common malignancy affecting the thyroid?

Answer 10

Papillary carcinoma

Question 11

Why must steroids be given before levothyroxine for treatment of a pituitary tumour?

Answer 11

Thyroxine can precipitate an adrenal crisis