Thyroid Disease

Question 1

What is another term for hyperthyroidism?

Answer 1

Thyrotoxicosis (high thyroid hormone levels, low TSH because pituitary gland senses you have enough thyroid hormone)

Question 2

Give the main potential causes of hypothyroidism

Answer 2

. Primary hypothyroidism (90% cases caused by Hashimoto’s autoimmune thyroiditis)
. Secondary to hypothalamus/anterior pituitary defect
. Iatrogenic (drug-induced, radiotherapy/surgery, lithium)
. Lack of dietary iodine
. Thyroid hormone resistance

Question 3

How would primary hypothyroidism affect the plasma concentrations of TSH and thyroid hormones? Would a goitre be present?

Answer 3

. Decrease in thyroid hormones (thyroid can’t produce much)
. Increase in TSH (anterior pituitary still working, but TSH can’t take effect so stays in blood)
. Goitre present (due to increased TSH over-stimulating thyroid gland)

Question 4

How would secondary hypothyroidism affect the plasma concentrations of TSH and thyroid hormones? Would a goitre be present?

Answer 4

. Decrease in thyroid hormones
. Decrease in TSH (hypothalamus produces less TRH–> less TSH from ant pit, or just ant pit dodgy so produces less TSH)

. Goitre not present because less TSH

Question 5

How would lack of dietary iodine, medical intervention, or thyroid hormone resistance affect the plasma concentrations of TSH and thyroid hormones?

Answer 5

. Decrease in thyroid hormones
. Increase in TSH (TSH still produced by functioning ant pit, but can’t have effect on dodgy thyroid)
. Goitre present (due to increased TSH over-stimulating thyroid gland)

Question 6

Give the main potential causes of hyperthyroidism

Answer 6

. Graves’ disease (autoimmune attack on thyroid= hypersecretion)
. Secondary to excess TRH/TSH secretion by hypothalamus/anterior pituitary
. Hyper-secreting thyroid tumour
. Iatrogenic (medications, lithium)

Question 7

What effect would Graves’ disease have on plasma levels of TSH and thyroid hormones? Would a goitre be present?

Answer 7

. Increase thyroid hormones, decrease TSH

. Goitre (even though decreased TSH, thyroid-stimulating antibodies over-stimulate thyroid gland)

Question 8

What effect would secondary hyperthyroidism have on plasma levels of TSH and thyroid hormones? Would a goitre be present?

Answer 8

. Increase TSH, increase thyroid hormones

. Goitre

Question 9

What effect would a tumour/iatrogenic causes of hyperthyroidism have on plasma levels of TSH and thyroid hormones? Would a goitre be present?

Answer 9

. Increase thyroid hormones, decrease TSH

. Goitre

Question 10

Why is a goitre always present with hyperthyroidism?

Answer 10

Because thyroid gland is overstimulated with TSH of TSIs (thyroid stimulating immunoglobulins), so becomes enlarged

Question 11

What is a goitre?

Answer 11

Enlargement of the thyroid gland

Question 12

What is a diffuse goitre? What is it caused by?

Answer 12

Whole thyroid gland enlarged due to overstimulation by excess TSH/TSIs

Question 13

What is a nodular goitre? What is it caused by?

Answer 13

Abnormal thyroid gland different from surroundings, often caused by tumour

Question 14

What is myxoedema?

Answer 14

Puffy appearance (face, hands, feet)
Skin thickened and dry

Question 15

What is cretinism?

Answer 15

Dwarfism and mental retardation (can occur in neonates with hypothyroidism- all newborns tested for T4 and TSH)

Question 16

What is the euthyroid state?

Answer 16

Normal thyroid state

Question 17

How do you test for hyper/hypothyroidism? What would the result be for primary and secondary hypothyroidism and hyperthyroidism?

Answer 17

. Thyroid function test (check levels of T3/T4 and TSH)
. Primary hypo: Low T3/T4, high TSH
. Secondary hypo: Low T3/T4, low TSH
. Primary hyper: High T3/T4, high TSH
. Secondary hyper: High T3/T4, high TSH

Question 18

How do you test for Hashimoto’s?

Answer 18

. Test for thyroid antibodies (TPO, anti-thyroid antibodies)

Question 19

How do you manage hypothyroidism? How do you manage hyperthyroidism?

Answer 19

Hypothyroidism: Give synthetic thyroid hormones, Levo-thyroxine (T4) or Liothyronine (T3)

Hyperthyroidism: Anti-thyroid drugs, surgery, radiotherapy

Question 20

Why is levo-thyroxine the drug of choice for hypothyroidism?

Answer 20

. Body can convert synthetic T4 to active T3, so can regulate amount used by body
. Longer half life, so doesn’t matter if patient forgets to take it once
. Liothyronine (synthetic T3) is very biologically active and the rapid onset can induce heart failure

Question 21

When must levo-thyroxine be used with caution? How can associated complications be avoided?

Answer 21

. Thyroid hormones act synergistically on beta-adrenoceptors with catecholamines and sympathetic NS
. Could uncover/worsen angina (increase HR etc.)
. Give beta-blocker alongside levo-thyroxine if patient has angina (check baseline ECG with initial dosage)

Question 22

When is liothyronine used over levo-thyroxine?

Answer 22

Liothyronine is used when a rapid effect is required, e.g. in severe hypothyroid state

Question 23

What is the most common cause of hypothyroidism? What is the most common cause of hyperthyroidism?

Answer 23

Hypothyroidism- Hashimoto’s
Hyperthyroidism- Graves’
(Both autoimmune)

Question 24

What is exophthalmos? What is it a symptom of? What is it caused by and how is it treated?

Answer 24

. Bilateral protrusion of eyes, common symptom of Graves’ disease (as well as goitre)
. Lipid proteins deposited in back of eyes, or
lymphocytes infiltrate soft tissue of eyes–> pushes eyes forwards
. Eye drops to lubricate so eyelids can close
. Surgery to remove lipid deposits

Question 25

How would you test for Graves' disease? How about a thyroid tumour?

Answer 25

. For Graves', test for thyroid-stimulating antibodies | . For tumour, use iodine-123 to do thyroid uptake test

Question 26

Anti-thyroid drugs are often given to treat hyperthyroidism. Give an example of two anti-thyroid drugs available in the UK. Which is the drug of choice?

Answer 26

. Thionamides: Carbimazole and propylthiouracil (PTU) | . Carbimazole usually drug of choice (unless adverse reaction, then use PTU)

Question 27

How does carbimazole work? What are the common side effects of carbimazole?

Answer 27

Inhibits TPO to inhibit iodination and coupling process (= decreased production of thyroid hormones) Common side effects: rashes, pruritus, can have bone marrow suppression

Question 28

How does propylthiouracil work?

Answer 28

Inhibits TPO and blocks conversion of T4 to T3

Question 29

Why do patients with Graves' disease often relapse after treatment?

Answer 29

They still have autoantibodies that attack the thyroid

Question 30

Why do anti-thyroid drugs take a few week to generate a response?

Answer 30

Colloid stores of thyroid hormones available in thyroid gland to continue using, and these have a long half-life

Question 31

How can symptoms of hyperthyroidism be relieved while anti-thyroid drugs (thionamides) are taking time to kick in?

Answer 31

. Use non-selective beta-blockers to reduce effect of catecholamines . Rapid relief of tremor, palpitations, anxiety (within 4 days)

Question 32

Two approaches to drug regimens with anti-thyroid drugs are 'dose titration' and 'block and replace'. What is the difference between these methods and which is more effective?

Answer 32

. Dose titration is when anti-thyroid drugs only are given . Block and replace is when T4 replacement is given alongside anti-thyroid drugs . Equally as effective, but dose titration associated with lower rate of side effects

Question 33

What is iodine-123 used for? What is iodine-131 used for?

Answer 33

. I-123 used to check if thyroid tumour present (uptake test) . Radioactive I-131 used for radiotherapy to destroy thyroid tumours (beta-emissions kill cells)

Question 34

Why can radioactive iodine be used to target thyroid tumours specifically?

Answer 34

Thyroid gland uptakes iodine (to synthesise thyroid hormones with tyrosine)

Question 35

When is radioactive iodine-131 first-line treatment? How is it administered? What is a potential negative effect?

Answer 35

. For older patients with hyperthyroidism and nodular goitres, when hyperthyroidism recurs after trying anti-thyroid drugs . Patient has single drink/capsule (maximum effect occurs 2-4 months after taking) . Can result in hypothyroidism