Thyroid

Question 1

What are the TSH and T4 levels in hypothyroidism?

Answer 1

TSH high, T4 low

Question 2

What are the TSH, T4 and TSI levels in hyperthyroidism?

Answer 2

TSH low, T4 high, TSI high

Question 3

What is the main concern for using levothyroxine?

Answer 3

Cardiac abnormalities (tachyarrhythmias, angina, MI)

Question 4

TSH goals for hypothyroidism

Answer 4

0.4-4 mIU/L

Question 5

How to take levothyroxine?

Answer 5

Empty stomach
30-60min before breakfast, 4h after dinner

Space apart from calcium/iron supplements, antacid, milk by ≥2h

Question 6

Target TSH in pregnancy for the different trimesters?

Answer 6

1st: <2.5
2nd: <3
3rd: <3.5

Question 7

Causes of hypothyroidism?

Answer 7

• iodine deficiency
• Hashimoto disease (autoimmune)
• iatrogenic (thyroid resection / radioiodine ablative therapy for hyperthyroidism)
• drug induced (secondary)

Question 8

What drugs can affect thyroid function and how?

Answer 8

• amiodarone: thyroiditis (hypo/hyper)
• lithium: thyroiditis (hyper), inhibit TH secretion & release (hypo)
• interferon alpha: thyroiditis (hyper > hypo)

Question 9

Can thyroid issues cause psychiatric disorders?

Answer 9

Yes (e.g. depression)

Question 10

Causes of hyperthyroidism?

Answer 10

• Graves disease (autoimmune, create TSI)
• adenomas
• drug induced

Question 11

Treatment options for hyperthyroidism?

Answer 11

• surgery
• radioactive iodine ablative therapy
• PTU, carbimazole
• propranolol (symptomatic)

Question 12

How does carbimazole and PTU work?

Answer 12

Inhibit iodination and synthesis of thyroid hormones
(PTU can block T4/T3 conversion at periphery at high doses)

Question 13

Doses of PTU and carbimazole?

Answer 13

PTU: higher numbers
Carbimazole: lower numbers

Question 14

Major concerns on using carbimazole and PTU?

Answer 14

Agranulocytosis (within 3m)
Hepatotoxicity (for PTU)

Question 15

Which trimester should you use which hyperthyroid drug and why?

Answer 15

1st: PTU (carbimazole increases risk of congenital malformations)
2nd & 3rd: carbimazole (PTU increases risk of hepatotoxicity and less potent)

Question 16

When are iodides for hyperthyroidism used?

Answer 16

• before surgery (7-10 days) to shrink gland
• after ablative therapy (3-7 days) to inhibit thyroiditis-mediated release of stored TH
• thyroid storm

Question 17

How do iodides work for hyperthyroidism?

Answer 17

• inhibit release of stored TH
• decrease vascularity and size of gland