Thyroid Disorders

Question 1

What is the endocrine system?

Answer 1

A collection of glands that secrete hormones directly into the circulation to be carried to distant organs

Question 2

What are the endocrine glands?

Answer 2

1. Hypothalamus
2. Pituitary glands
3. Pineal gland
4. Thyroid gland
5. Parathyroid glands
6. Thymus gland
7. Adrenal gland
8. Pancreas
9. Ovary
10. Testes

Question 3

What is the function of the thyroid gland?

Answer 3

Synthesis, storage and secretion of thyroxine (T4) and triiodothyronine (T3)

Question 4

How does thyroid stimulation work?

Answer 4

1. The hypothalamus releases thyrotrophin releasing hormone.
2. This then stimulates the anterior pituitary to release thyroid stimulating hormone.
3. TSH stimulates the thyroid to produce T3 &T4

If T3 is too high - negative feedback to anterior pituitary to stop releasing TSH

If T4 too high - negative feedback to hypothalamus to stop producing TRH

Question 5

What do T3 and T4 do?

Answer 5

1. Stimulate metabolism - lipid and carbohydrate
2. Influence growth and development
3. Other effects on CNS, CV and reproductive system

Question 6

Who is affected most by hypothyroidism?

Answer 6

Women (5-10x more) associated with CV disease

Question 7

Who is affected by thyrotoxicosis?

Answer 7

CV disease and osteoporosis

Question 8

How would you investigate thyroid disease?

Answer 8

1. Suspect in people with depression or unexplained anxiety
2. Measure free T3 and T4 levels only if abnormal TSH

Question 9

What is hypothyroidism?

Answer 9

Decreased production of thyroid hormones

Question 10

What does hypothyroidism cause?

Answer 10

Slowing down of body processes due to decreased metabolic function

Question 11

What is the onset of hypothyroidism?

Answer 11

30-60 years old

Question 12

What causes primary hypothyroidism?

Answer 12

1. Post-operative hypothyroidism
2. Anti-thyroid drugs
3. Auto-immune hypothyroidism

Question 13

What causes secondary hypothyroidism?

Answer 13

1. Hypopituitarism - deficiency in hormones made
2. Hypothalamic disease

Question 14

What are the signs and symptoms of hypothyroidism?

Answer 14

1. Weight gain
2. Fatigue
3. Constipation
4. Depression
5. Being sensitive to cold
6. Muscle aches and weakness
7. Muscle cramps

Question 15

How do you treat hypothyroidism?

Answer 15

Levothryoxine sodium - maintain TSH levels within ref range but this may take 6 months to achieve

1. Starting dose (adults 18-49) - 50 to 100 micrograms daily
2. Increase dose by 25-50 micrograms every 3-4 weeks according to response
3. Maintenance dose - 100 to 200 micrograms daily
4. Starting dose (adults over 50 or cardiac disease) - 25 - 50 micrograms daily
5. Preferably taken 30 mins before breakfast or caffeine containing liquids

Question 16

What is hyperthyroidism?

Answer 16

Excessive production and secretion of thyroid hormone

Question 17

What does hyperthyroidism cause?

Answer 17

Increased metabolism of all body systems

Question 18

What causes hyperthyroidism?

Answer 18

1. Graves’ disease (toxic diffuse goitre)

• thyroid stimulating antibodies mimic the effects of TSH
• overactivity of the thyroid gland
• inflammation of tissue around the eye
• genetic predisposition

2. Toxic nodular goitre

• single hyperfunctioning nodule

Question 19

What are the signs and symptoms of hyperthyroidism?

Answer 19

1. Nervousness, anxiety and irritability
2. Mood swings
3. Difficulty sleeping
4. Persistent tiredness and weakness
5. Sensitivity to heat/increased sweating
6. Swelling in neck due to enlarged goitre
7. Palpitations

Question 20

How would you treat hyperthyroidism?

Answer 20

1. Anti thyroid drugs, initially supplemented by beta blockers
2. Radioactive iodine
3. Surgery

Question 21

How do antithyroid drugs work?

Answer 21

They prevent thyroid hormone synthesis

Question 22

What antithyroid drugs are used to treat hyperthyroidism?

Answer 22

1. Carbimazole - initially 15-40 mg daily progressively reduced to a maintenance dose of 5-15 mg daily

• take FBC and LFT before starting
• take for 12-18 months

2. Propylthiouracil - initially 200-400 mg daily reduced to a maintenance dose of 50-150 mg daily

• used if there is a sensitivity to carbimazole (2nd line)

3. Beta blockers - propranolol 20-40 mg 2 to 4 times daily

• rapid relief of palpitations, anxiety, sweating and tremor
• used adjunct to radioactive iodine and carbimazole in the first few weeks

Question 23

What is the blocking replacement regimen?

Answer 23

Giving high dose carbimazole (40 - 60mg/day) to block production and levothyroxine (50 - 150 micrograms/day) to supplement for 4 - 6 weeks

Question 24

What are the S/E’s of carbimazole?

Answer 24

1. Neutropenia
2. Agranulocytosis
3. Recognition of bone marrow suppression
4. Patients should report signs and symptoms of infection esp sore throat
5. Stop promptly if clinical or lab evidence of neutropenia

Question 25

Radioactive iodine (131I)…

Answer 25

1. Is safe - most patients become hypothyroid 2. C/I in children, pregnancy and breastfeeding 3. Euthyroidism within 2-3 months

Question 26

Surgery…

Answer 26

1. Patients should be biochemically euthyroid 2. Iodine 10-14 days before surgery 3. Less frequently used