Hypothyroidism and Hyperthyroidism

Question 1

What are causes of hypothyroidism?

Answer 1

1) Hashimoto’s thyroiditis (autoimmune, most common cause)
2) Radiotherapy/surgery for hyperthyroidism or cancer in the neck area (over correction)
3) Failure of delivery of thyroid hormones int he fetus causing cretinism (problem with neurological problems)
4) Central pituitary tumour
5) Late effects from chemotherapy using newer chemotherapeutic agents with endocrine side effects e.g. ipilimumab (tyrosine kinase inhibitors)

Question 2

Describe the features of Hashimoto’s thyroiditis

Answer 2

• Autoimmune
• Antibodies attack thyroid peroxidase or thyroglobulin (anti-TPO or anti-Tg) and are elevated
• Women more commonly affected aged 30-50
• Strong genetic component - need good FH, screen relatives

Question 3

Which thyroidism is it easier to treat?

Answer 3

Hyperthyroidism

Question 4

How can a central pituitary tumour lead to hypothyroidism?

Answer 4

• Non-functional tumour compressing pituitary gland

- Low TSH causing secondary hypothyroidism

Question 5

How do you diagnose hypothyroidism?

Answer 5

1) Elevated TSH (reduced feedback from T3 and T4)
2) Decreased free T3 and T4
3) Presence of anti TPO/anti Tg antibodies

Question 6

What two antibodies are elevated in Hashimoto’s thyroiditis?

Answer 6

1) Anti-thyroid peroxidase (anti-TPO)

2) Anti-thyroglobulin (anti-Tg)

Question 7

What are is the treatment for hypothyroidism?

Answer 7

1) Thyroxine (T4) - well tolerated, life long treatment, restores TSH
2) Liothyronine (sodium salt of T3) - more for acute treatment in severe case, replace with thyroxine when better

Question 8

What is myxoedema?

Answer 8

• Profound hypothyroidism
• Decreased GCS (coma)
• Presents with heart failure
• Most often TSH is undetectable or v highly elevated
• Severe goitre
• Poor prognosis

Question 9

What is goitre?

Answer 9

• Increase in size of thyroid gland

- Causes = hypothyroidism, hyperthyroidism, iodine deficiency

Question 10

What is iodine deficiency?

Answer 10

• <50μg/day
• Dietary iodine requirement 150μg/day
• Leads to formation of non-toxic goitre
• Treat with iodine supplements, decrease intake of goitrogen

Question 11

What is a goitrogen?

Answer 11

• A substance containing high iodine that suppress hormone secretion, so increases TSH secretion and causes formation of goitre
• e.g. litium, iodine in kep (seaweed), brassicae (cabbage), cassava, some local drinking water, cough mixtures

Question 12

What are the 4 main symptoms of hypothyroidism?

Answer 12

1) Cold intolerance
2) Weight gain
3) Constipation
4) Slow reflexes

Question 13

What are the 4 main signs of hypothyroidism?

Answer 13

1) Dry skin
2) Hoarse voice
3) Slow movements
4) Coarse hair

Question 14

What are other common but not the main symptoms/signs of hypothyroidism?

Answer 14

1) Fatigue
2) Generalised swelling/oedema - fluid retention
3) Periorbital puffiness
4) Hypercholesterolaemia
5) Heart failure - from profound hypothyroidism

Question 15

What are the physiological effects of hypothyroidism?

Answer 15

1) Increase body weight
2) Decrease oxygen consumption
3) Decreased heat production
4) Decrease BMR
5) Drowsiness
6) Decreased reflexes
7) Decreased sympathetic effects
8) Bradycardia + decrease in CO and BP
9) Decrease in gut effects

Question 16

What is the relationship between thyroid hormones, TSH and hypothyroidism?

Answer 16

• Initially have a low T3 and T4 and then the TSH slowly starts to rise
• The higher the TSH, increased morbidity and mortality - can lead to myxoedema coma

Question 17

What are causes of hyperthyroidism?

Answer 17

1) Graves’ disease
2) Thyroiditis
3) Toxic nodule
4) hCG-induced hyperthyroidism
5) TSH-producing pituitary gland tumour - stimulates thyroid, rare
6) Amiodarone induced
7) Factitious
8) Struma ovarii- ovarian tumour which can produce excess thyroxine

Question 18

What happens in Graves’ disease?

Answer 18

• Autoimmune disease
• Thyroid-stimulating antibody (TSAb) binds to and causes prolonged stimulation of TSH receptors or TSHRAb stimulates the thyroid repetitively
• Therefore actually have low TSH as all the thyroid hormone circulating negatively feedbacks to decrease TSH production

Question 19

How does hCG cause hyperthyroidism?

Answer 19

• hCG has the same structure as TSH

- So in the first trimester of pregnancy can have hyperthyroidism due to high levels of hCG

Question 20

What is amiodarone and why can it cause hyperthyroidism?

Answer 20

• Anti-arrhythmic medication

- Can upset thyroid function due to its iodine content

Question 21

What is factitious hyperthyroidism?

Answer 21

Hyperthyroidism due to people taking too much thyroxine due to maybe underlying psychiatric problem or attention seeking

Question 22

What are the two types of treatment for hyperthyroidism?

Answer 22

1) Anti-thyroid drugs

2) Beta blocked - to treat cardiovascular symptoms

Question 23

What are the two types of antithyroid drugs used to treat hyperthyroidism?

Answer 23

1) Carbimazole

2) Propylthiouracil (PTU)

Question 24

Describe treatment of hyperthyroidism with anti-thyroid drugs

Answer 24

• Inhibit thyroid peroxidase
• PTU also prevents peripheral conversion of T4 to T3
• Treat for 18 months
• Side effects = low WCC, can drop to 0 (neutropenia and agranulocytosis), sore throat (infection), skin rash
• Carbimazole has better side effect profile except low WCC, used first
• PTU safer in pregnancy and breastfeeding
• 60% relapse rate

Question 25

What beta blocker is used to treat cardiovascular symptoms linked to hyperthyroidism?

Answer 25

Propranolol - blocks sympathetic effects of hormones esp. on heart

Question 26

Describe treatment of hyperthyroidism with radioiodine

Answer 26

- Taken up into follicular cells and irradiates them (kills them) - Given as drink - Achieves remission in 80-90% - Causes hypothyroidism in almost all patients and patients normally end up on thyroxine forever - Side effect = dry mouth (sialadenitis) due to uptake by salivary glands and occasional nausea (side effects not bad) - Can worsen Graves' orbitopathy - don't give if eye disease is bad, otherwise can give steroids with it - Used instead of surgery

Question 27

When is radioiodine used to treat hyperthyroidism?

Answer 27

When there is a relapse of Graves' after anti-thyroid medication

Question 28

What antibody test is used to diagnose Graves' disease?

Answer 28

- TSH receptor antibody (TSHRAb) is the most sensitive - it is elevated in almost 100% of cases of Graves'

Question 29

What surgery can be used for hyperthyroidism?

Answer 29

Partial thyroidectomy

Question 30

What drug is used to treat hyperthyroidism if antithyroid drugs don't work (to try and avoid surgery)?

Answer 30

Radioiodine (131I)

Question 31

When is surgical treatment for hyperthyroidism considered?

Answer 31

1) Uncontrolled thyrotoxicosis on anti-thyroid medication - younger women often quite resistant to this medication 2) Cannot tolerate any other forms of therapy due to bad side effects e.g. low WCC, severe nausea or vomiting 3) Very large goitre - unlikely to respond to radioiodine 4) Refractory amiodarone-induced cases

Question 32

What do you give before surgery for hyperthyroidism?

Answer 32

Iodine in LUGOL’S solution (5% I2 + 10% KI) - used prior to surgery to reduce vascularity of thyroid gland to reduce blood loss

Question 33

What are the top 6 symptoms of hyperthyroidism?

Answer 33

1) Anxiety, nervousness (insomnia) 2) Sweating 3) Heat intolerance 4) Palpitations 5) Fatigue 6) Weight loss

Question 34

What are the top 6 signs of hyperthyroidism?

Answer 34

1) Tachycardia 2) Tremor on outstretched hands 3) Thyroid bruit - increase thyroid blood volume 4) Eye signs - ophthalmopathy 5) Goitre - thyroid is working hard, smoothly enlarged goitre throughout bc thyroid is producing too much T4 6) Skin changes

Question 35

What are other symptoms and signs of hyperthyroidism

Answer 35

1) SoB (palpitations) 2) Weakness - proximal myopathy bc of increased catabolic state - lose muscle mass 3) Diarrhoea 4) Leg swelling - can be linked to heart failure 5) Menstrual irregularity - oligomenorrhoea 6) Atrial fibrillation - due to uncontrolled long time thyrotoxicosis (blood clots and stroke) 7) Pre-tibial myxoedema - thickening of skin over tibia due to deposition of glycosaminoglycans

Question 36

Describe the eye symptoms in hyperthyroidism

Answer 36

- Exophthalmos - upper and lower sclera and eyeballs are prominent and protruded (proptosis) - normally can't see the lower sclera - Upper lid retraction

Question 37

What investigations would you do to diagnose hyperthyroidism?

Answer 37

1) TSH (low) 2) Free T4/T3 (high) 3) Testing for antibodies e.g. TSH receptor antibody (TSHRb) or TSAb 4) Thyroid uptake scan

Question 38

How can Hashimoto's cause transient hyperthyroidism?

Answer 38

- Anti-TPO antibodies cause inflammation and destroy the thyroid gland - Therefore whatever is in the thyroid (thyroid hormones) spills into the circulation - This causes a transient hyperthyroid state which will eventually will go back to normal or become hypothyroid

Question 39

How can a thyroid uptake scan diagnose thyroid problems?

Answer 39

- If overactive, thyroid increases uptake of technetium (contrast) so it looks very dark - if consistent in both lobes = Graves' - If only just a patch of darkness/uptake e.g. lower part of left lobe this would indicate a toxic nodule - When there is barely any uptake (light grey, fuzzy) this indicates destructive thyroiditis incl. Hashimoto's

Question 40

What are the physiological effects of hyperthyroidism?

Answer 40

1) Decrease body weight 2) Increase oxygen consumption 3) Increased heat production 4) Increased BMR 5) Insomnia, excitability 6) Increased reflexes 7) Increased sympathetic effects 8) Tachycardia + increase in CO and BP 9) Increase in gut effects