Hypothyroidism and Hyperthyroidism Flashcards
What are causes of hypothyroidism?
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)
Describe the features of Hashimoto’s thyroiditis
- 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
Which thyroidism is it easier to treat?
Hyperthyroidism
How can a central pituitary tumour lead to hypothyroidism?
- Non-functional tumour compressing pituitary gland
- Low TSH causing secondary hypothyroidism
How do you diagnose hypothyroidism?
1) Elevated TSH (reduced feedback from T3 and T4)
2) Decreased free T3 and T4
3) Presence of anti TPO/anti Tg antibodies
What two antibodies are elevated in Hashimoto’s thyroiditis?
1) Anti-thyroid peroxidase (anti-TPO)
2) Anti-thyroglobulin (anti-Tg)
What are is the treatment for hypothyroidism?
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
What is myxoedema?
- Profound hypothyroidism
- Decreased GCS (coma)
- Presents with heart failure
- Most often TSH is undetectable or v highly elevated
- Severe goitre
- Poor prognosis
What is goitre?
- Increase in size of thyroid gland
- Causes = hypothyroidism, hyperthyroidism, iodine deficiency
What is iodine deficiency?
- <50μg/day
- Dietary iodine requirement 150μg/day
- Leads to formation of non-toxic goitre
- Treat with iodine supplements, decrease intake of goitrogen
What is a goitrogen?
- 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
What are the 4 main symptoms of hypothyroidism?
1) Cold intolerance
2) Weight gain
3) Constipation
4) Slow reflexes
What are the 4 main signs of hypothyroidism?
1) Dry skin
2) Hoarse voice
3) Slow movements
4) Coarse hair
What are other common but not the main symptoms/signs of hypothyroidism?
1) Fatigue
2) Generalised swelling/oedema - fluid retention
3) Periorbital puffiness
4) Hypercholesterolaemia
5) Heart failure - from profound hypothyroidism
What are the physiological effects of hypothyroidism?
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
What is the relationship between thyroid hormones, TSH and hypothyroidism?
- 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
What are causes of hyperthyroidism?
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
What happens in Graves’ disease?
- 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
How does hCG cause hyperthyroidism?
- hCG has the same structure as TSH
- So in the first trimester of pregnancy can have hyperthyroidism due to high levels of hCG
What is amiodarone and why can it cause hyperthyroidism?
- Anti-arrhythmic medication
- Can upset thyroid function due to its iodine content
What is factitious hyperthyroidism?
Hyperthyroidism due to people taking too much thyroxine due to maybe underlying psychiatric problem or attention seeking
What are the two types of treatment for hyperthyroidism?
1) Anti-thyroid drugs
2) Beta blocked - to treat cardiovascular symptoms
What are the two types of antithyroid drugs used to treat hyperthyroidism?
1) Carbimazole
2) Propylthiouracil (PTU)
Describe treatment of hyperthyroidism with anti-thyroid drugs
- 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
What beta blocker is used to treat cardiovascular symptoms linked to hyperthyroidism?
Propranolol - blocks sympathetic effects of hormones esp. on heart
Describe treatment of hyperthyroidism with radioiodine
- 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
When is radioiodine used to treat hyperthyroidism?
When there is a relapse of Graves’ after anti-thyroid medication
What antibody test is used to diagnose Graves’ disease?
- TSH receptor antibody (TSHRAb) is the most sensitive - it is elevated in almost 100% of cases of Graves’
What surgery can be used for hyperthyroidism?
Partial thyroidectomy
What drug is used to treat hyperthyroidism if antithyroid drugs don’t work (to try and avoid surgery)?
Radioiodine (131I)
When is surgical treatment for hyperthyroidism considered?
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
What do you give before surgery for hyperthyroidism?
Iodine in LUGOL’S solution (5% I2 + 10% KI) - used prior to surgery to reduce vascularity of thyroid gland to reduce blood loss
What are the top 6 symptoms of hyperthyroidism?
1) Anxiety, nervousness (insomnia)
2) Sweating
3) Heat intolerance
4) Palpitations
5) Fatigue
6) Weight loss
What are the top 6 signs of hyperthyroidism?
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
What are other symptoms and signs of hyperthyroidism
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
Describe the eye symptoms in hyperthyroidism
- Exophthalmos - upper and lower sclera and eyeballs are prominent and protruded (proptosis) - normally can’t see the lower sclera
- Upper lid retraction
What investigations would you do to diagnose hyperthyroidism?
1) TSH (low)
2) Free T4/T3 (high)
3) Testing for antibodies e.g. TSH receptor antibody (TSHRb) or TSAb
4) Thyroid uptake scan
How can Hashimoto’s cause transient hyperthyroidism?
- 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
How can a thyroid uptake scan diagnose thyroid problems?
- 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
What are the physiological effects of hyperthyroidism?
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
