Hypothyroidism

Question 1

What are primary causes of hypothyroidism?

Answer 1

Hashimoto’s thyroiditis

Iodine deficiency (most common worldwide)

Atrophic thyroiditis

Iatrogenic= secondary to radiation damage which might be used to treat lymphoma

Congenital

Infiltration of thyroid due deposits from sarcoidosis and amylodosis

Virtual thyroiditis

Question 2

What are secondary causes of hypothyroidism?

Answer 2

Hypopituitarism= tumours or Sheehans disease or infection can lead to decreased in TSH production

Medication

• lithium inhibits production of thyroid hormones
• amiodarone= interferes with thyroid hormone production and metabolism

Treatment for hyperthyroidism

Question 3

What is the pathology behind Hashimoto’s thyroiditis?

Answer 3

AI condition associated with production of antithyroid peroxidase antibodies (anti-TPO) and antithyroglobulin antibodies

Question 4

How might someone with hypothyroidism present?

Answer 4

Weight gain 
Fatigue 
Dry skin 
Coarse hair and hair loss
Fluid retention= oedema/pleural effusion/ascites 
Heavy or irregular periods 
Constipation 
Intolerance for cold 
Bradycardia 
Goitre

Question 5

How would you differentiate between primary and secondary hyperthyroidism on a TFT?

Answer 5

Primary

• low T3/4
• high TSH= due to lack of negative feedback leading to pituitary increasing the production of TSH to try and raise T3/4 levels

Secondary

• low T3/4
• low TSH= problem lies in the pituitary i.e. decreased TSH production is the cause of low thyroid hormone levels

Question 6

Apart from TFT what other bloods would you want to order in suspected hypothyroidism and why?

Answer 6

Autoantibodies

• anti-TPO
• anti-thyroglobulin

Raised CK= due to myofibre degeneration in the severe hypothyroidism

FBC= may have signs of anaemia

Question 7

Why might a patient with hypothyroidism develop anaemia?

Answer 7

Hypothyroid state leads to decreased bone marrow activity which leads to decreased production of RBC

Question 8

How is hypothyroidism managed?

Answer 8

Primary:

• levothyroxine= synthetic T4 which is metabolised to T3 in the body
• treat deficiency if present with iodine supplements

Stop drugs which can interfere with thyroid hormone production

• ferrous sulphate
• calcium supplements
• Rifampicin
• amiodarone

Secondary
-treat the cause= tumour

Question 9

How does pregnancy impact the management of hypothyroidism?

Answer 9

Need to have increased monitoring= each trimester

Need to be u-thyroid before pregnancy

Increase levothyroxine dose= increased demand during pregnancy