Thyroid Disorders

Question 1

What is the physiology of thyroid function hormones?

Answer 1

The hypothalamus releases TRH which travels to the anterior pituitary = TSH is produced by the anterior pituitary and travels to the thyroid gland to produce T4. T3 is produced by the peripheral conversion of T4 to T3 and T3 is more active.

T3 and T4 travel in the blood bound to thyroxine-binding globulin.

T3 and T4 increase cell metabolism and increase Catecholamine effects,

Question 2

What is the difference between the serum levels of free T3 and T4 and total T3 and T4?

Answer 2

Total T3 and T4 is bound to TBG, and thus is increased when TBG is increased.

Free T3 and T4 is a more accurate representation.

Question 3

What conditions can increase TBG?

Answer 3

Pregnancy
Oestrogen therapy (HRT, COCP)
Hepatitis

Question 4

What conditions can decrease TBG?

Answer 4

Nephrotic syndrome and malnutrition (due to protein loss)
Drugs (androgens, corticosteroids, phenytoin)
Chronic liver disease
Acromegaly

Question 5

What is the general presentation of TFTs in hyperthyroidism?

Answer 5

Decreased TSH

Raised T4

Question 6

What is the general presentation of TFTs in hypothyroidism?

Answer 6

TSH varies throughout the day (trough at 2pm)

Question 7

What patients must have their TFTs screened?

Answer 7

AF
Hyperlipidaemia
Diabetes mellitus
Patients on amiodarone or lithium
Downs, Turners, Addisons

Question 8

What hormone profile will you see in hypothyroidism?

Answer 8

Increased TSH

Decreased T4

Question 9

What hormone profile will you see in a patient with treated hypothyroidism or sub clinical hypothyroidism?

Answer 9

Raised TSH

Normal T4

Question 10

What hormone profile will you see in patients with a TSH secreting tumour or thyroid hormone resistance?

Answer 10

Raised TSH

Raised T4

Question 11

What hormone profile will you see in a patient with hyperthyroidism?

Answer 11

Decreased TSH

Increased T4 or T3

Question 12

What hormone profile will you see in a patient with sub clinical hyperthyroidism?

Answer 12

Low TSH

Normal T3 and T4

Question 13

What hormone profile will you expect to see in a patient with sick euthyroidism or pituitary disease?

Answer 13

Decreased TSH

Decreased T4 and T3

Question 14

What are the signs of hypothyroidism?

Answer 14

BRADYCARDIC
Reflexes slow
Ataxia (cerebellar)
Dry thin hair/skin
Yawning/drowsy/coma
Cold hands and decreased temperature
Ascites and non pitting oedema
Round puffy face/double chin 
Defeated demeanour
Immobile
CCF

Question 15

How do you diagnose hypothyroidism?

Answer 15

Increased TSH
Decreased T4

Increased cholesterol and triglycerides
Macrocytosis

Question 16

What are the causes of primary autoimmune hypothyroidism?

Answer 16

Primary atrophied hypothyroidism (lymphocytic infiltration of thyroid leading to atrophy, hence no goitre)

Hashimoto’s thyroiditis (goitre due to lymphocytic infiltration. Older women.

Question 17

What are the causes of primary hypothyroidism?

Answer 17

Iodine deficiency (1)
Post thyroidectomy
Drug induced (anti thyroid drugs, amiodarone, lithium, iodine)

Question 18

What is secondary hypothyroidism?

Answer 18

Not enough TSH (due to hypopituitarism)

Question 19

What is the treatment of primary hypothyroidism?

Answer 19

Healthy and young: levothyroxine 0-100mcg/24h. Review at 12 weeks

Elderly or IHD: levothyroxine 25mcg/24h, increase by 24mcg/4weeks according to TSH

Question 20

If someone has already been given levothyroxine and the diagnosis of hypothyroidism is being debated, what should you do?

Answer 20

Stop levothyroxine

Recheck TSH in 6 weeks

Question 21

How can amiodarone cause thyroid problems?

Answer 21

Amiodarone is iron rich and structurally like T4. Some patients on amiodarone may begin to have their T4 release inhibited, resulting in hypothyroidism

Question 22

When should you suspect sub clinical hypothyroidism?

When should you treat it?

Answer 22

Suspect if TSH >4 with normal T3 and T4.

Treat if 
TSH >10
Positive thyroid autoantibodies
Past Graves' disease
Other organ specific autoimmunity

Question 23

What are the symptoms of thyrotoxicosis?

Answer 23

Tremor
Sweating
Weight loss
Tachycardia
Exaggerated reflexes
Palpitations
Oligomenorrhoea and infertility
Chorea
Itch
Urticaria

Question 24

What are the signs of thyrotoxicosis?

Answer 24

Irregular or fast pulse
Warm moist hands
Fine tremor
Palmar erythema
Lid lag
Goitre or thyroid nodules may be present

Question 25

What are the specific symptoms of Graves’ disease?

Answer 25

1) Exophthlamos/ophthalmoplegia

2) Pretibial myxoedema

Question 26

What do tests show in thyrotoxicosis?

Answer 26

Decreased TSH (suppressed), T4 and increased T3
Increased ESR, calcium, and LFTs 
Check thyroid autoantibodies

Question 27

What are the causes of thyrotoxicosis?

Answer 27

Graves' disease
Toxic multinodular goitre
Toxic Adenoma
Ectopic thyroid tissue
Exogenous

Question 28

What happens in Graves’ disease?

Answer 28

Typical in 40-60 year olds and caused by circulating IgG autoantibodies that bind to and activate thyrotopin receptors, which cause thyroid enlargement and increased hormone production.

Stress, infection, and childbirth can trigger it.

Question 29

What happens in toxic multinodular goitre?

What happens in toxic Adenoma?

Answer 29

Seen in the elderly
Nodules in the thyroid that secrete thyroid hormones

Toxic Adenoma: Singular nodule producing T3 and T4, looks hot on isotope scan

Question 30

What medications can you use to treat thyrotoxicosis?

Answer 30

Beta blockers: propranolol 40mg/6h for rapid control of symptoms

Anti thyroid medications:
Regimen 1: Carbimazole for 4wks, reduce according to TFTs every 1-2m.
Regimen 2: Carbimazole and levothyroxine simultaneously

In Graves, maintain either regimen for 12 months then withdraw

Question 31

What is the main SE of carbimazole?

Answer 31

Agranulocytosis

Question 32

Apart from drugs, what are the other treatments of thyrotoxicosis?

Answer 32

Radio iodine (most become hypothyroid post treatment. CI are pregnancy and lactation)
Thyroidectomy