Endocrine - Hypothyroidism

Question 1

What is primary hypothyroidism?

Answer 1

Thyroid produces inadequate thyroid hormones

No negative feedback
High TSH
Low T3/T4

Question 2

What is secondary hypothyroidism?

Answer 2

AKA Central hypothyroidism

Pituitary doesn’t produce enough TSH

Low TSH
Low T3/T4

Question 3

Complete the table

Answer 3

Question 4

What is the most common cause of primary hypothyroidism?

Answer 4

Hashimoto’s thyroiditis
In developed countries
Autoimmune condition causing inflammation
Anti-TPO and anti-Tg antibodies

Iodine deficiency
Developing countries

Question 5

What treatments for hyperthyroidism can cause hypothyroidism?

Answer 5

Carbimazole
Propylthiouracil
Radioactive iodine
Thyroidectomy

Question 6

What drugs can cause hypothyroidism?

Answer 6

Lithium
- Inhibits production of T3/4

Amiodarone
- Interferes with production and metabolism
- Can also cause thyrotoxicosis

Sodium Valproate

Question 7

What are some causes of secondary hypothyroidism?

Answer 7

Associated with a lack of pituitary hormones e.g. ACTH

• Tumours
• Pituitary surgery
• Radiotherapy
• Sheehan’s syndrome (major post-partum haemorrhage causes avascular necrosis of the pituitary gland)
• Trauma

Question 8

How does hypothyroidism present?

Answer 8

Weight gain
Fatigue
Dry skin
Fluid retention
Heavy or irregular periods

Question 9

What is the mainstay of treatment for hypothyroidism?

Answer 9

Oral levothyroxine

Levothyroxine is synthetic T4 which metabolises to T3

Question 10

How is dosage decided for hypothyroidism?

Answer 10

Based on TSH level every 4 weeks