Pharmacology: Thyroid and Pituitary Disease Drugs

Question 1

Name the modes of administration of testosterone

Answer 1

Sustanon - IM every 3-4 weeks)

Skin gel (testogel, tostral)

Nebido - prolonged IM injection 10-14 weeks

Oral tablets (rarely used)

Question 2

What is the indication for propylthiouracil?

Answer 2

First line for hyperthyroidism only in first trimester of pregnancy

Question 3

Describe the mechanism of action of carbimazole

Answer 3

Inhibition of TPO thereby blocking thyroid hormone synthesis

Question 4

What is the indication for carbimazole?

Answer 4

First line for hyperthyroidism

Question 5

What are the potential side effects of propylthiouracil?

Answer 5

Allergic type reactions, agranulocytis

Liver damage - cholestatic jaundice, increased liver enzymes, 1: 10 000 risk of fulminant hepatic failure (monitor LFTs)

Question 6

Describe the side effects of levothyroxine

Answer 6

Usually occur when dose is too high, resulting in hyperthyroidism - increased appetite, weight loss, increased sweating etc.

Question 7

How would you ‘safety net’ a patient on carbimazole or propylthiouracil?

Answer 7

Warn patient verbally and in writing to stop drug and have urgent FBC checked in the event of fever, oral ulcer or oropharyngeal infection - agranulocytosis

Question 8

Why should you monitor FBC in patients prescribed testosterone?

Answer 8

Can cause polycythaemia - cause risk of stroke/MI

Question 9

What is the indication for testosterone?

Answer 9

Hypopituitarism resulting in testosterone deficiency

Question 10

Why should you use β-blockers with caution in asthmatics and what can you prescribe instead?

Answer 10

Risk of provoking bronchospasm

CCBs e.g. diltiazem can be useful instead

Question 11

What is levothyroixine?

Answer 11

Manufactured form of thyroxine (T4)

Question 12

Name 3 medications which can impair absorption of levothyroxine

Answer 12

PPIs, iron tablets, calcium tables

Question 13

Describe the mechanism of action of propylthiouracil

Answer 13

Inhibits DIO1 which decreases conversion of T4 to T3

Question 14

What effects may propylthiouracil have on a foetus?

Answer 14

Risk of aplasia cutis in early pregnancy

Risk of liver toxicity to foetus

Question 15

Describe the mechanism of action of β-blockers

Answer 15

β-adrenoceptor blockade - reduced activity of sympathetic nervous system

Question 16

Why is carbimazole contraindicated in the first trimester of pregnancy, and used in the rest of pregnancy in as low a dose as possible?

Answer 16

Risk of aplasia cutis in early pregnancy

Low dose to minimise other side effects on foetus when taken in pregnancy:

• Scalp abnormalities
• GI abnormalities
• Choanal and oesophageal atresia

Question 17

What is the indication for β-blockers in hyperthyroidism?

Answer 17

Immediate symptomatic relief of thyrotoxic syptoms

Question 18

Dose requirements of levothyroxine may increase by 25-50% in ________

Answer 18

Pregnancy

Question 19

Name two side effects of carbimazole

Answer 19

Allergic type reactions, agranulocytosis

Question 20

Why is propranalol the β-blocker of choice for symptomatic relief of hyperthyroidism?

Answer 20

Inhibits DIO1 as well as blocking β-adrenoceptors

Question 21

Why should you check PSA in a patient before you prescribe testosterone and monitor PR exam?

Answer 21

Testosterone causes prostate enlargement - does not cause prostate cancer but may cause it to grow

Question 22

What are the indications for levothyroxine?

Answer 22

Hypothyroidism and hypopituitarism

Question 23

Name a potential side effect of oral testosterone

Answer 23

Hepatitis

Question 24

What are the potential side effects of β-blockers?

Answer 24

Generally well tolerated

Nausea, headaches, tiredness